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  • 1401.
    Yi, Changping
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Zhang, Ping
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Shirzadegan, Shahin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nyberg, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Numerical modelling of dynamic response of underground openings under blasting based on field tests2016Ingår i: Proceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction / [ed] E. Nordlund, T.H. Jones and A. Eitzenberger (eds), 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to assess the capacity of ground support systems when subjected to dynamic loading, simulated rockburst tests by using blasting have been conducted at LKAB Kiirunavaara underground mine. In this paper, a numerical simulation for one of the field tests is conducted using LS-DYNA code to numerically investigate the effect of the different aspects of the charge design including the initiation point and the geometry on the test results. In the simulation, an explosive material model is used to model the detonation of explosive used in field tests and the Riedel-Hiermaier -Thoma (RHT) material model is used to model the dynamic response of the rock mass. The decoupling effect between the explosive and the wall of borehole is also taken into account in the model. The numerical results show a similar particle vibration pattern and a crack pattern to those of the field measurment. The effects of the position of the initiation point and the charge structure on the dynamic response of rock mass are also discussed. The results can be a reference for blast design for future field tests.

  • 1402.
    Yi, Xiaoping
    et al.
    Central South University of Technology, Changsha.
    Sun, Zongqi
    Central South University of Technology, Changsha.
    Ouchterlony, Finn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Stephansson, Ove
    Kungliga tekniska högskolan, KTH.
    Fracture toughness of Kallax gabbro and specimen size effect1991Ingår i: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 28, nr 2/3, s. 219-223Artikel i tidskrift (Refereegranskat)
  • 1403.
    Yi, Xiaoping
    et al.
    Laurentian University.
    Sun, Zongqi
    Central South University of Technology, Changsha.
    Ouchterlony, Finn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Stephansson, Ove
    Luleå tekniska universitet.
    Specimen size effect of the fracture toughness of Kallax gabbro1992Ingår i: Rock mechanics: proceedings of the 33rd U.S. Symposium, Sweeney Convention Center, Santa Fe, New Mexico 3 - 5 June 1992 / [ed] J R Tillerson; W Waversik, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1992, s. 847-856Konferensbidrag (Refereegranskat)
  • 1404. Young, Raymond N.
    et al.
    Nakano, Masashi
    Pusch, Roland
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Environmental soil properties and behaviour2012Bok (Refereegranskat)
    Abstract [en]

    Examining the many changes in soil properties and behavior as a result of stresses from both anthropogenic and environmental forces, this critical work details the requirements of soils to maintain their design engineering properties (rheological, transmission, buffering, and ion-accumulation) over their projected life-spans. It discusses the use of soils as engineered materials in the construction of structures on and in the ground, including foundations, bridges, nuclear waste repositories, tunnels, and other civil infrastructures. The book presents numerous laboratory tests, procedures, techniques, data gathering, data reduction models, and analyses of soil structure.

  • 1405.
    Yousif, Ali A.
    et al.
    Water Resources Engineering Department, College of Engineering, University of Duhok, Duhok, Iraq.
    Sulaiman, Sadeq Oleiwi
    Dams and Water Resources Department, College of Engineering, University of Anbar, Ramadi, Iraq.
    Diop, Lamine
    UFR S2ATA, Sciences Agronomiques, de l’Aquaculture et des Technologies Alimentaires, Université Gaston Berger (UGB), Saint Louis, Sénégal.
    Etheram, Mohammad
    Department of Water Engineering and Hydraulic Structures, Faculty of Civil Engineering, Semnan University, Semnan, Iran.
    Shahid, Shamsuddin
    School of Civil Engineering, Faculty of Engineering, Universiti Teknologi Malaysia, Johor Bahru, Malaysia.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Yaseen, Zaher Mundher
    ustainable Developments in Civil Engineering Research Group, Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam.
    Open Channel Sluice Gate Scouring Parameters Prediction: Different Scenarios of Dimensional and Non-Dimensional Input Parameters2019Ingår i: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 11, nr 2, artikel-id 353Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The determination of scour characteristics in the downstream of sluice gate is highly importantfor designing and protection of hydraulic structure.  The applicability of modern data-intelligence technique known as extreme learning machine (ELM) to simulate scour characteristics has been examined in this study.  Three major characteristics of scour hole in the downstream of a sluice gate, namely the length of scour hole (Ls), the maximum scour depth (Ds), and the position of maximum scour depth (Lsm), are modeled using different properties of the flow and bed material. The obtained results using ELM were compared with multivariate adaptive regression spline (MARS). The dimensional analysis technique was used to reduce the number of input variable to a smaller number of dimensionless groups and both the dimensional and non-dimensional variables were used to model the scour characteristics. The prediction performances of the developed models were examined using several statistical metrics. The results revealed that ELM can predict scour properties with much higher accuracy compared to MARS. The errors in prediction can be reduced in the range of 79%–81% using ELM models compared to MARS models. Better performance of the models was observed when dimensional variables were used as input. The result indicates that the use of ELM with non-dimensional data can provide high accuracy in modeling complex hydrological problems.

  • 1406.
    Zainy, Maher
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Bauer, Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ask, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    The Tectonic and Structural Classifications of the Western Part of the Zagros Fold and Thrust Belt, North Iraq, Review and Discussion2017Ingår i: Journal of Earth Sciences and Geotechnical Engineering, ISSN 1792-9040, Vol. 7, nr 2, s. 71-89Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Zagros fold and thrust belt represents a tectonically significant area, and one

    of the richest areas in oil and gas reservoirs in the world. The Zagros fold and

    thrust belt is the deformational product of the Cretaceous-present day convergence

    of the Arabian and Iranian (Eurasian) plates (subduction and collision). The belt

    extends more than 2000 km from southern Turkey through the north and

    northeastern Iraq to the Strait of Hormuz in southwestern Iran. The Zagros fold

    and thrust belt is divided into two parts which are; Western part within Iraqi

    region and Eastern part within Iranian region. The western part of the Zagros fold

    and thrust belt has been traditionally subdivided into several structural zones that

    are generally striking parallel to the plate boundary. This is characterized by

    exposure of Late Ordovician to Pliocene - Pliestocene formations with different

    types of Quaternary Sediments. This research will concentrate on Western part of

    Zagros fold and thrust belt and the styles of structural classifications, which will

    aid to clarify and better understand the tectonic and structural history and

    evolution of the region. We have considered the last version of structural

    classification as the most relevant one to the reality, especially within outer

    platform (Unstable shelf). Where it divides the region into four structural zones,

    which are: Low Folded zone, High Folded Zone, Imbricate Zone, and Zagros

    Suture Zone and these zones were further divided to several subzones. This

    classification is based on the structural style and intensity of deformation,

    stratigraphy, mechanicalstratigraphy and tectono-stratigraphy of the deformed

    sequences, Age of deformation, surface physiography and morphology. The data

    used in the classification is more reliable, up to date and relevant.

  • 1407.
    Zainy, Maher T.
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Bauer, Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ask, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    The Tectonic and Structural Classifications of the Western Part of the Zagros Fold and Thrust Belt, North Iraq, Review and Discussion2017Ingår i: Journal of Earth Sciences and Geotechnical Engineering, ISSN 1792-9040, E-ISSN 1792-9660, Vol. 7, nr 2, s. 71-89Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Zagros fold and thrust belt represents a tectonically significant area, and one of the richest areas in oil and gas reservoirs in the world. The Zagros fold and thrust belt is the deformational product of the Cretaceous-present day convergence of the Arabian and Iranian (Eurasian) plates (subduction and collision). The belt extends more than 2000 km from southern Turkey through the north and northeastern Iraq to the Strait of Hormuz in southwestern Iran. The Zagros fold and thrust belt is divided into two parts which are; Western part within Iraqi region and Eastern part within Iranian region. The western part of the Zagros fold and thrust belt has been traditionally subdivided into several structural zones that are generally striking parallel to the plate boundary. This is characterized by exposure of Late Ordovician to Pliocene - Pliestocene formations with different types of Quaternary Sediments. This research will concentrate on Western part of Zagros fold and thrust belt and the styles of structural classifications, which will aid to clarify and better understand the tectonic and structural history and evolution of the region. We have considered the last version of structural classification as the most relevant one to the reality, especially within outer platform (Unstable shelf). Where it divides the region into four structural zones, which are: Low Folded zone, High Folded Zone, Imbricate Zone, and Zagros Suture Zone and these zones were further divided to several subzones. This classification is based on the structural style and intensity of deformation, stratigraphy, mechanicalstratigraphy and tectono-stratigraphy of the deformed sequences, Age of deformation, surface physiography and morphology. The data used in the classification is more reliable, up to date and relevant.

  • 1408.
    Zainy, Maher T.
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bauer, Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Ask, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Geometric Analysis of the Minor Structures in Iraqi Part of the Zagros Belt, NE Iraq2018Ingår i: 9th International Symposium on Eastern Mediterranean Geology 07-11 May 2018 Antalya-Turkey: Abstracts and Proceedings Book / [ed] M. Gurhan Yalcin, Yasemin Leventeli, Turkey: Academic Conferences Publishing, 2018, s. 324-324Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Geometric analysis was carried out on part of the Zagros Belt, along the border between Iraq andIran, within rocks of Cretaceous age, which are composed of alternative sequences of competentand incompetent layers, and it contains a number of minor structures. The minor folds identifiedwithin the study area have different shapes, orientations and sizes, and exhibit high intensityfolding. Their wave length and amplitude range from few centimeters up to tens of meters. They areranged from gentle to tight according to the Fleuty, 1964 classification. Class 1B is dominated andfollowed by class 1C according to the Ramsay, 1967. The orientation of the minor folds, theirrelation with the major structures, variance in their shapes and sizes and difference interlimb angle,all indicate that they were developed progressively and in harmony with the major structuredevelopment. It can be concluded that the congruous and subcongruous minor folds weredeveloped successively during a single phase of deformation with simulation of variouscompressive stress directions (generally, at NE-SW and E-W), and the reorientation of the stressfield from one direction to another is attributed to the oblique collision between the Arabian andEurasian plates and to the anticlockwise rotation of the Arabian plate relative to Eurasian plate.

  • 1409.
    Zakaria, Saleh
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Rain water harvesting and supplemental irrigation at Sinjar district in northwest Iraq2012Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Rainwater harvesting is one of the methods that can ensure availability of water for winter crop in Iraq. Using this technique the excess rainwater (runoff) is stored in reservoirs of dams of different sizes. The water from these reservoirs can be used later when required to satisfy the crops requirements.It is believed that rainwater harvesting will be one of the solutions to overcome water shortages problem in Iraq.This work deals with rainwater harvesting modeling on Sinjar District. The area of study is a plan area located on the northern and southern flank of Sinjar Mountain, within Nineveh province in northwest Iraq. The model was first applied on southern of Sinjar Mountain, where barley crop was chosen as one of the main crops grown in the area. Linear programming technique was adopted to optimize the irrigated area for irrigation scenario of supplemental irrigation (SI) 100% of full irrigation requirements. Two scenarios of operation were considered for each main basin. In the first, each reservoir was operated as a separate unit while in the second all reservoirs in a basin were operated as one system. Both scenarios gave encouraging results. Scenario two however, was relatively better.And then the model was applied again on the northern Sinjar Mountain area. Wheat crop was considered as the main crop grown in the area. A linear programming technique was adopted to optimize the irrigated area for three scenarios of irrigation. They were: 1/supplemental irrigation (SI) 100%, 2/deficit irrigation (DI) 50%, 3/deficit irrigation (DI) 25% of full irrigation requirements. The results of the three scenarios used indicated that, using deficit irrigation (DI) of 50% can be more beneficial than SI of 100% and DI of 25% of full irrigation requirements. These results reflect useful value of RWH and its influence to increase the irrigated area in the studied region.This study had been carried out at Lulea University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Lulea, Sweden.The present work structured in seven chapters, and can be pursued as follows: In chapter 1, Background of the rainwater harvesting, aims of study and research methodology are addressed. In chapter 2, Scope of description of Water Resources in Iraq, Numbers and facts about Iraq, Present water resources conditions in Iraq, Irrigation practices in Iraq, Main Rivers of Iraq, Dams on Tigris and Euphrates Rivers, The impact of Southeastern Anatolia Project (GAP) on water resources in Iraq, Environmental Consequences and Groundwater in Iraq are described.In chapter 3, Information review on rainwater harvesting and supplemental irrigation is presented. In chapter 4, Description of the study area of the Sinjar District, simulation models used in the study and a research methodology are presented.In chapter 5, The results are presented and discussed for southern and northern of Sinjar Mountain. In chapter 6, Summaries for future study: water harvesting and groundwater recharge, water harvesting and its role in increasing crop productivity and the impact of forecasting on water harvesting. In chapter 7, Summaries for the overall conclusions based on the results and then references of the study are listed.Extended of thesis 1-Water harvesting and reservoir optimization of selected areas south Sinjar Mountain, Iraq, Lulea University of Technology, Sweden.Nadhir Al-Ansari, Mohammad Ezz-Aldeen, Sven Knutsson, Saleh Zakaria Submitted to the Journal of Hydrological Engineering. 2- Rainwater harvesting and supplemental irrigation at northern Sinjar Mountain, Iraq, Lulea University of Technology, Sweden.Saleh Zakaria, Nadhir Al-Ansari, Sven Knutsson, Mohammad Ezz-Aldeen Journal of Purity, Utility Reaction and Environment, Vol. 1 No.3,May 2012, 121-141.

  • 1410.
    Zakaria, Saleh
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Rain Water Harvesting (RWH) North of Iraq2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Rainwater harvesting is one of the methods that can ensure availability of water for winter crop in Iraq. Using this technique the excess rainwater (runoff) is stored in reservoirs of dams of different sizes. The water from these reservoirs can be used later when required to satisfy the crops requirements. It is believed that rainwater harvesting will be one of the solutions to overcome water shortages problem in Iraq.This work includes four parts dealing with macro rainwater harvesting modeling. The study area includes selected sites at three Governorates located north of Iraq (Erbil, Sulaymaniyah, and Nineveh). In part one of the work, three selected sites at south, north and east of Sinjar district (Nineveh Governorate) were used. The slope of the study area at Sinjar district is less than 5%. The technique was first applied on southern Sinjar Mountain. Linear programming technique was adopted to optimize the irrigated area of barley crop for irrigation scenario of supplemental irrigation (SI) 100% of full irrigation requirements. Two scenarios of reservoir operation were considered for each main basin. In the first, each reservoir was operated as a separate unit while in the second all reservoirs in main basin were operated as one system. Both scenarios gave encouraging results. Scenario two however, was relatively better. The technique was applied again on the northern and eastern Sinjar Mountain area but with different catchments area and scenarios of irrigation (supplemental irrigation (SI) 100%, deficit irrigation (DI) 50%, and deficit irrigation (DI) 25% of full irrigation requirements). Wheat crop was considered as the main crop grown in the area. A linear programming technique was adopted to optimize the irrigated area for the above three scenarios of irrigation. The results of the three scenarios used indicated that, using deficit irrigation (DI) of 50% can be more beneficial than SI of 100% and DI of 25% of full irrigation requirements. Part two of the work includes application of Macro RWH technique at mountain areas in Northeastern part of Iraq. In these areas, all selected basins having slope more than 5 % and located at the rain-fed farms of Kurdistan region of Iraq, Erbil and Sulaymaniyah Governorates. The annual rainfall is greater than what was available at Nineveh Governorate. Part three of the work focused about the ability of Macro RWH technique to support wheat crop yield production in dry rain-fed farms at north Sinjar district, north west of Iraq, using wheat crop yield-water relationship that conducted by International Center for Agricultural Research in the Dry Areas (ICARDA). Three scenarios of supplemental irrigation (100%, 75% and 50%) of full irrigation. requirements with, various rainfall conditions were used, two types of wheat (bread and durum) were considered. Part four of the work focused on climatic change and future prospects for Macro RWH technique. Box-Jenkins methodology for time series analysis and forecasting (ARIMA model) was used to study future rainfall for 4 main rainfall stations surrounding Sinjar area in order to forecast expected rainfall for the period 2012-2016. Future rainfall depths were forecasted with adoption of a confidence level of 95%. The future rainfall was employed for RWH technique. This part also includes a review of the impact of climatic change on countries of the Middle East and North Africa (MENA region). The climatic model CGCM3.1 (T47) 2 was used to explain the changes in the average temperatures and rainfall on MENA region with special emphases on Iraq. Long term future seasonal rainfall during the period 2020-2099 at east Sinjar (Nineveh Governorate) showed a clear negative trend reflecting the reduction in total seasonal rainfall amount. For these future rainfall depths, the maximum, minimum and average harvested runoff volumes were estimated. The comparison of the runoff results between future and historical recorded rainfall for the same study area was carried out to show the future validity of rainwater harvesting. In order to estimate the amount of runoff that can be harvested from a given catchment area at eastern Sinjar, an attempt was made to provide set of charts that are easy to be used in order to estimate the equivalent harvested runoff depth (mm) for different selected rainfall depths under different hydraulic conditions for the catchment area. Macro rainwater harvesting (RWH) technique had been tested for future rainfall data that predicted by two emission scenarios of climatic change (A2 and B2) for the period 2020-2099 at Nineveh and Sulaymaniyah Governorates north of Iraq. The results of the four parts of the thesis reflect useful values for RWH and its influence to increase the irrigated area and then the crop yield in the studied region when combined with an effective system like supplemental irrigation. Rain-fed land in the studied areas requires effective technique in terms of saving significant runoff water for irrigation purposes and this might be achieved by rain-water harvesting (RWH) technique.

  • 1411.
    Zakaria, Saleh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Dawood, Anwer
    Koya University.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Future Prospects for Macro Rainwater Harvesting Technique at Northwest Iraq2014Ingår i: Journal of Earth Sciences and Geotechnical Engineering, ISSN 1792-9040, E-ISSN 1792-9660, Vol. 4, nr 1, s. 1-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rainfall data is part of the main components in the hydrological cycle and firmly associated with almost all aspect of climate. Previous research indicated that Macro rainwater harvesting techniques (RWH) can be implemented successfully in Sinjar area northwest Iraq. Recently, prediction of rainfall trends in the Middle East and Iraq in particular suggest a decrease in rainfall due to climate change. This raises the question about the future validity of RWH in the area.In this research, the validity of RWH was investigated using predicted rainfall data in Sinjar area. Eight seasons were selected representing different decades that start 2020 to 2099. The results showed that the maximum, minimum and average harvested future runoff volumes reached about 28.5, 7.61, and 13.9 million cubic meters, that may occurred during the seasons 2055-2056, 2046-2047, and 2065-2066 respectively. The resultant harvested runoff volumes produced by four selected basins at Eastern Sinjar as a catchment area with total area of 435.15 km2. In the second part, an attempt had been made to provide the study area by a set of charts that can help in estimating daily runoff under dry, wet and normal conditions for rainfall depths that ranged between 15 to 55 mm.

  • 1412.
    Zakaria, Saleh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Ezz-Aldeen, Mohammad
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Rain water harvesting at eastern Sinjar mountain, Iraq2012Ingår i: Geoscience Research, ISSN 0976-9846, E-ISSN 0976-9854, Vol. 3, nr 2, s. 100-108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Iraq is facing water shortages and the problem is becoming more serious with time. The main water resources of Iraq (Tigris and Euphrates Rivers) suffer from severe reduction in their discharges due to construction dams on the both banks of Rivers inside Turkey and Syria. Agricultural land had been reduced drastically due to water scarcity. Despite this fact, none of the Iraqi farmers had yet used non-conventional techniques to augment water resources to overcome water shortage problems such as Rainwater Harvesting (RWH) technique.The main aim of this research is to contribute to solving the problem of water shortage of Iraq by finding effective results in terms of saving significant runoff water for irrigation purposes, and therefore provide an academic effort as a tool for encourage and decision support for RWH in Iraq.Macro RWH (large catchment area), was applied at East Sinjar Mountain in Iraq. The estimating volume of harvested runoff ranged (0.11-28.11) ×106 m3 calculated using the Watershed Modeling System (WMS) for the four selected basins together with total area of 435.14 km2 for the study period of (1990-2009).The results of estimating runoff volume showed that the runoff volume can be considered for irrigation practices especially in supplementary irrigation.A linear programming technique was adopted to maximize the irrigated area. Three scenarios of irrigation level were chosen: supplemental irrigation (SI) 100% Satisfy full irrigation requirements (S1), deficit irrigation (DI) 50% of full irrigation requirements (S2), and deficit irrigation (DI) 25% of full irrigation requirements (S3). The resultant irrigated area ranged between 18-2646 for SI 100%, 58-41303 for DI 50%, and 27-9543for DI 25% hectares respectively for all four selected basins together. These results reflect useful value of RWH and its influence to increase the irrigated area in the studied region.

  • 1413.
    Zakaria, Saleh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Historical and future climatic change scenarios for temperature and rainfall for Iraq2013Ingår i: Journal of Civil Engineering and Architecture, ISSN 1934-7359, E-ISSN 1934-7367, Vol. 7, nr 12, s. 1574-1594Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The world is facing a big challenge of climatic change, mainly due to increasing concentrations of greenhouse gases (GHGs) in the atmosphere. Many researches indicated that the climate change occurred disproportionately on developing countries such as Middle East and North Africa (MENA) countries.The climatic model CGCM3.1 (T47) 2 is used in this research to explain the changes in average temperatures and the rainfall on MMENA region with special emphases on Iraq. Historical records (1900-2009) and future (2020-2099) were studied and compared, each period was divided to four sub-periods of thirty years. The results showed that the average monthly temperature for the four historical periods fluctuated between the lowest and highest value as follows: 9.2-32.9, 10.3-32.7, 9.3-32.8, and 8.6-33.9 (Cº).The rainfall for historical periods kept on the same distribution during the past 109 years, and fluctuated between the lowest and highest value of 21.3 and 37.6 mm with an average that reached up to 26.51 mm. For the future period, the maximum average monthly temperature reached up to 37.41 (Cº) during June and minimum average monthly temperature reached up to 4.24 (Cº) during January. The average monthly temperature fluctuated giving a clear impression that the future portends a higher temperature. The average monthly of rainfall, for the future period, fluctuated between the lowest and highest value of 12.91 and 20.63 mm with an average that reached 16.84 mm which represent a reduction percentage of about 36.47% relative to the historical record of rainfall for the same months.

  • 1414.
    Zakaria, Saleh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Rainwater harvesting using recorded and hypothetical rainfall data scenarios2013Ingår i: Journal of Earth Sciences and Geotechnical Engineering, ISSN 1792-9040, E-ISSN 1792-9660, Vol. 3, nr 2, s. 21-42Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Macro Rainwater Harvesting (RWH) under recorded and forecasting rainfall scenarios helps to overcome the water shortage problem. Eastern Sinjar District-Iraq had been investigated for the potential of RWH with a catchment area of four basins. Three recorded rainfall scenarios (S1, S2, and S3) were diagnosed representing seasons of the maximum, minimum and average weekly rainfall events for the period 1990-2011. Forecasting the rainfall depths for the same catchment area were estimated depending on Box-Jenkins methodology to build Autoregressive Integrated Moving Average (ARIMA) models for weekly rainfall data for the period 2012-2016. Three forecasting rainfall scenarios (S4, S5, and S6) were diagnosed to represent the seasons of the maximum, minimum and average weekly forecasting rainfall events. The results of these scenarios were compared with an average area to be irrigated obtained from the results of 19 years record. The results indicated that in wet years RWH technique with supplemental irrigation help to give total irrigated area larger than a total specified average irrigated area. In average and dry years, the amounts of the additional needed water were estimated to irrigate the total areas that should be increase in order to satisfy the specified average irrigated area.

  • 1415.
    Zakaria, Saleh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Wheat yield scenarios for rainwater harvesting at northern Sinjar mountain, Iraq2013Ingår i: Journal of Natural Science, ISSN 0075-4307, Vol. 5, nr 10, s. 1057-1068Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Iraq is part of West Asia and North Africa (WANA) region. The area is known as dry land, famous with gap of crop yield as a result of the water shortage problem.Six basins with total catchment area of 614.19 km2 at rain-fed of Northern Sinjar District-Iraq had been chosen to investigate both of the potential of rainwater harvesting (RWH) and three supplemental irrigation (SI) scenarios S1, S2, and S3 (100%, 75%, and 50% of full irrigation requirement) to support the wheat yield (bread and durum) under various rainfall conditions for the study period 1990-2009.The results indicated that, the total volume of harvested runoff can be considered for irriga- tion practices, that reached up to 42.4 , 25.1, 0.6, 10.9 (*106 m3) during 1995-1996, 1996-1997, 1998-1999, and 2001-2002, respectively.The total irrigated area ranged between 10.9-5163.7 and 8.8-3595.7 (ha) for bread and durum wheat crop for the four selected seasons respectively. The yield scenarios for supplemental irrigation condition Y1, Y2, and Y3 give 68–9712, 94–12999, and 105–22806 Ton for bread wheat, and for durum wheat give 56–8035, 87–10906, and 103–17396 Ton.

  • 1416.
    Zakaria, Saleh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Al-Badrany, Thafer
    University of Mosul.
    ARIMA Models for weekly rainfall in the semi-arid Sinjar District at Iraq2012Ingår i: Journal of Earth Sciences and Geotechnical Engineering, ISSN 1792-9040, E-ISSN 1792-9660, Vol. 2, nr 3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Time series analysis and forecasting is an important tool which can be used to improve water resources management. Iraq is facing a severe water shortage problem. The use of rainwater harvesting is one of the techniques to overcome this problem. To put this into practice, it is of prime importance to forecast future rainfall events on a weekly basis.Box-Jenkins methodology has been used in this research to build Autoregressive Integrated Moving Average (ARIMA) models for weekly rainfall data from four rainfall stations in the North West of Iraq: Sinjar, Mosul, Rabeaa and Talafar for the period 1990-2011. Four ARIMA models were developed for the above stations as follow: (3,0,2)x(2,1,1)30, (1,0,1)x(1,1,3)30, (1,1,2)x(3,0,1)30 and (1,1,1)x(0,0,1)30 respectively. The performance of the resulting successful ARIMA models were evaluated using the data year (2011).These models were used to forecast the weekly rainfall data for the up-coming years (2012 to 2016). The results supported previous work that had been carried out on the same area recommending the use of water harvesting in agricultural practices.

  • 1417.
    Zakaria, Saleh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Ezz-Aldeen, Mohammad
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Rain water harvesting and supplemental irrigation at northern Sinjar mountain, Iraq2012Ingår i: Journal of Purity, Utility Reaction and Environment, ISSN 2232-1179, Vol. 1, nr 3, s. 121-141Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Iraq is facing water shortages and the problem is becoming more serious with time. Despite this fact, none of the farmers had used Rainwater Harvesting (RWH) technique yet. The main aim of this research is to contribute to solving the problem of water shortage of Iraq by finding effective results in terms of saving significant runoff water for irrigation purposes. Macro RWH was applied at Northern Sinjar Mountain in Iraq, where macro is indicator for large catchment area. Runoff volume was determined by applying the watershed modeling system (WMS) for six selected basins with total area of 614.19km2 for the study period of (1990-2009). The volume of harvested water ranged (0.6-42.4) × 106 m3 for all six basins together for the study period. A linear programming technique was adopted to optimize the irrigated area for three scenarios of irrigation, 1/ supplemental irrigation (SI) 100%, 2/ deficit irrigation (DI) 50%, 3/ deficit irrigation (DI) 25% of full irrigation requirements. The results of calculation of irrigated area ranged between 14.5-3663.7 for SI 100%, 33.0-39827.1 for DI 50%, and 20.1-7314.0 for DI 25% hectares respectively. These results reflect useful value of RWH and its influence to increase the irrigated area in the studied region.

  • 1418.
    Zakaria, Saleh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mustafa, Yaseen
    Zakho University.
    Alshibli, Mohammad
    Ministry of Water Resources.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Macro rain water harvesting network to estimate annual runoff at Koysinjaq (Koya) district, Kurdistan region of Iraq2013Ingår i: Engineering, ISSN 1947-3931, E-ISSN 1947-394X, Vol. 5, nr 12, s. 956-966Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Macro rainwater harvesting techniques (Macro RWH) are getting more popular to overcome the problem of water scar-city in arid and semi-arid areas. Iraq is experiencing serious water shortage problem now despite the presence of Tigris and Euphrates Rivers. RWH can help to overcome this problem. In this research RWH was applied on Koya city in its districts, North West Iraq. Twenty two basins were identified as the catchment area for the application of RWH tech-nique. Watershed modeling system (WMS), based on Soil Conservation Service - curve number (SCS-CN) method, was applied to calculate direct runoff from individual daily rain storm using average annual rainfall records of the area. Two consecutive adjustments for the curve number were considered. The first was for the antecedent moisture condition (AMC) and the second was for the slope. These adjustments increased the total resultant harvested runoff up to 79.402 *106 m3. The average percentage of increase of harvested runoff volume reached 9.28%. This implies that water allocation is of the order of 2000 cubic meter per capita per year. This quantity of water will definitely help to develop the area.

  • 1419.
    Zakaria, Saleh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mustafa, Yaseen
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Ahmed, Payman
    Ghafour, Bahra
    Rainwater harvesting at Koysinjaq (Koya), Kurdistan region, Iraq2013Ingår i: Journal of Earth Sciences and Geotechnical Engineering, ISSN 1792-9040, E-ISSN 1792-9660, Vol. 3, nr 4, s. 25-46Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Macro Rainwater Harvesting (RWH) has been tested at Koysinjaq (Koya) District, Kurdistan region of Iraq, due to its limited source of water.The studied area consists of four basins with total area of 228.96 km2. The estimating volumes of harvested runoff for the four selected basins together for the study period (2002-2011) were calculated using the Watershed Modeling System (WMS) which is based on Soil Conservation Service Curve Number (SCS-CN) method.In this research, a comparison between maximum and minimum rainfall seasons was conducted to give better understanding for the events that is governing the harvested runoff collection.The results show that, the total harvested runoff ranged from14.83 to 80.77(*106 m3) from the four selected basins together. This indicates that the technique of Macro RWH can be considered to provide a new source of water to contribute to reduce the problem of water scarcity.

  • 1420.
    Zakaria, Saleh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mustafa, Yassen
    Zakho University.
    Mohammed, Diary
    Sulaimaniya University.
    Ali, Salahalddin
    Sulaimaniya University.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Estimation of annual harvested runoff at Sulaymaniyah Governorate, Kurdistan region of Iraq2013Ingår i: Journal of Natural Science, ISSN 0075-4307, Vol. 5, nr 12, s. 1272-1283Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Kurdistan Region (KR) of Iraq has suffered from the drought period during the seasons 2007- 2008 and 2008-2009 that affected the human and economic activities of the region. Macro rain- water harvesting (Macro RWH) is one of the te- chniques that can ensure water availability for a region having limited water resources. This te- chnique is based on Soil Conservation Service- Curve Number (SCS-CN) method and the Water- shed Modeling System (WMS) was used to esti- mate the runoff. Rainfall records of Sulaymani- yah area for the period 2002-2012 were studied and an average season was selected (2010-2011). The results of the application of the WMS model showed that about 10.76 million cubic meters could be harvested. The results also showed that the quantity of the harvested runoff was highly affected by rainfall depth, curve number values, antecedent moisture conditions (AMC) and the area of the basins.

  • 1421.
    Zardari, Muhammad Auchar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mechanical properties of fine grained, sulphur rich, silty soils2010Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Tailings are the waste products produced during extraction of minerals from the ore. The particle size of tailings varies from medium sand to silt or clay size. Tailings are used as a construction material for raising of embankments called tailings dams. During spigotting, the coarse particles (sands) lie close to the embankment, while the fine particles (slimes) move downwards to the impoundment. The rate of failure in tailings dams is higher than that for the conventional water dams. In the past, tailings dams have failed due to various causes such as meteorological incidents, slope instability, piping/seepage, weak foundations, and seismic liquefaction etc. The statistics shows that the tailings dams are not safe even in their construction stages. The closure and reclamation measures require that the tailings dams and impoundments should be stable for a long time (more than 1000 years). Hence, the proper understanding of the mechanical properties (i.e., permeability, stiffness and strength) of tailings is essential in order to make reliable predictions for the long time stability of tailings dams and impoundments. The purpose of the literature survey carried out is: (a) to understand the mechanical properties of tailings material regarding anisotropy, cyclic loading, particle crushing and creep effects; (b) to know the current design practice and identify the factors that may have strong influence on the long time stability of tailings dams and impoundments, and (c) to find from literature, an appropriate constitutive model that can predict realistic behaviour of tailings material. There is similarity in properties of coarse tailings and loose to medium dense natural sands. Slimes are complex material and may show resemblance to natural sands, clays, or a combination of both. The hydraulic conductivity of tailings varies from point to point in a deposit. Tailings are more compressible than the natural soils. The coefficient of consolidation of slimes is in the range shown by natural clays. Due to high particle angularity, the sands and slimes show higher drained shear strength than that for similar natural soils. Undrained strength of sands is important in evaluation of liquefaction behaviour. The embankments can be raised with upstream, downstream or centreline construction methods. The upstream method is susceptible to liquefaction, whereas the downstream and centreline methods are relatively seismic resistant. The stability of the tailings embankments can be enhanced by keeping the phreatic surface low within the embankment body. The phreatic surface can be lowered with the application of cores, drainage zones, and the use of sand tailings in the embankment construction. Cut-off trenches, slurry walls, grout curtains, and liners can control seepage in tailings dams.The pore water pressures develop during construction of tailings embankments. These pore pressures are described as initial static pore pressure, initial excess pore pressure, and pore pressure due to shearing. The stability analyses conditions for conventional water dams (such as end of construction, staged construction, and long term) are also applicable to the tailings dams. The end of construction condition, and staged construction condition of a tailings dam can be analysed with undrained strength analysis. The drained analysis can be used for the long-term condition of a tailings dam (when an embankment attains maximum height and is constructed slowly). The aim of reclamation measures for tailings dams and impoundments is to achieve long time mass stability, environmental safety, and productive land use. Tailings impoundments can be stabilized with ripraps, chemicals, vegetation, and dry/wet covers etc.Most natural soils show anisotropy in strength due to their depositional history. Due to low density and high degree of saturation, tailings show large cyclic strains in a few cycles of stress reversal. The cyclic strength of tailings can increase with decreasing void ratio. Creep occurs in all soils. Clays show more creep than sands. Loose sands creep more than dense sands. The loads due to high tailings embankments may cause particle crushing and creep. The long time stability of tailings dams and impoundments can be predicted with finite element analysis with suitable constitutive models. The numerical analysis needs to be carried out for severe conditions of rainfalls, floods, and earthquakes.

  • 1422.
    Zardari, Muhammad Auchar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Numerical analyses of stability of a gradually raised tailings dam2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Numerical analyses are presented in this thesis to address potential stability problems that may occur during gradual raisings and under seismic loading conditions of Aitik tailings dam in northern Sweden. The dam is mainly raised using upstream construction method. It is planned to raise the dam gradually in several stages. Two dam parts were studied. The first dam part is a straight dam portion, and the second dam part is a corner. The main concerns associated with future raisings of the straight dam part were: (i) the stability of the dam could be affected by an increase in excess pore pressures during sequential raisings, (ii) how to gradually strengthen the dam by using rockfill berms as supports in such a way that required slope stability can be achieved with a minimum volume of rockfill berms, and (iii) if the dam is subjected to seismic loading, whether or not an increase in excess pore pressures could lead to extensive liquefaction which may cause a failure. The problems related to the dam corner were that tension zones and/or low compression zones could develop because of the horizontal pressure of the stored tailings on the inside of the curvature of the dam corner.Numerical analyses were conducted on both the dam parts using finite element method. Two dimensional (2D) plane strain finite element model was utilized to analyse the straight dam. The dam corner was analysed with both the three dimensional (3D) finite element model, and the 2D axisymmetric finite element model. Coupled deformation and consolidation analyses, and slope stability analyses were performed on both the dam parts to simulate gradual raisings, and to compute safety factors. In addition to this, dynamic analyses were carried out on the straight dam part to evaluate the potential for liquefaction, and seismic stability of the dam. The seismic behaviour of the dam was analysed for two cases: (i) a normal case (earthquake of 3.6 Swedish local magnitude), and (ii) an extreme case (earthquake of 5.8 moment magnitude).The results of the straight dam part, with only previously existing rockfill berms, indicate that stability of the dam was reduced due to an increase in excess pore pressures during raisings. Rockfill berms were utilized as supports to raise the dam with enough safety. An optimization technique was utilized to minimize the volume of rockfill berms. This technique could result in significant saving of cost of rockfill berms.The results of the dam corner show that tension zones and/or low compression zones were located on the surface of the dam corner, mainly above the phreatic level. It is interpreted that there is no risk of internal erosion through the embankments because no seepage path occurs above the phreatic level, and a filter zone exists along the slope of the dam. It is suggested to gradually strengthen the dam corner with rockfill berms. The results of the 2D axisymmetric analyses of the dam corner were in a fairly good agreement with those of the 3D analyses. This implies that the 2D axisymmetric analyses are valid for this dam corner. This is an important finding as 2D axisymmetric analyses require much less computational time compared to 3D analyses.The results of the dynamic analyses performed on the straight dam (including additional rockfill berms) suggest that, for the extreme case, liquefaction could occur in a limited zone that is located below the surface near the embankments. For both the normal and the extreme case, (i) seismically induced displacements seem to be tolerable, and (ii) the post seismic stability of the dam is considered to be sufficient.The findings of this study have been practically applied to the Aitik tailings dam. In general, the modelling procedure and the optimization technique to minimize volume of rockfill berms, presented in this study, could be applied to other tailings dams.

  • 1423.
    Zardari, Muhammad Auchar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Stability of tailings dams: focus on numerical modelling2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Upstream tailings dams may experience slope stability problems when the rate of raising is too fast. Tailings consolidate slowly due to low hydraulic conductivity. The excess pore pressures can build up due to accelerated rate of raising. The cumulative increase in excess pore pressures due to successive raisings can endanger slope stability of a tailings dam. The stability of a tailings dam is closely related to the consolidation process. The consolidation process and associated stability of an upstream tailings dam during staged construction was modelled with the finite element program PLAXIS. The analysis indicated that the stability of the dam reduced during raising due to increase of excess pore pressures. The safety of the dam was improved by adding rockfill banks on the downstream side. The volume of the rockfill banks was minimized with an optimization technique. This technique involves (i) construction of a rockfill bank on the downstream side when the factor of safety is less than a permissible limit, (ii) utilization of a minimum volume of the rockfill that is necessary to stabilize the slope. This technique can be practicable when the rate of raising is moderate, and partial consolidation occurs between consecutive raisings. Numerical analysis was also performed on a curved embankment of an upstream tailings dam in order to investigate the possible risk of hydraulic fracturing and internal erosion in a corner of the dam. The analysis showed that low compressive stresses occurred above the phreatic level, near the zones of filter and rockfill banks. These zones contain coarse material, and are, therefore, not susceptible to hydraulic fracturing and internal erosion. An increase in the radius of the corner is suggested in order to prevent large reductions in compressive stresses that may occur due to future raisings. Presently the curved dam section is stable. However, an additional rockfill bank on the downstream side will be required for future raisings. Static liquefaction is considered as a common cause of disastrous flow failures of tailings dams. These flow failures can be predicted with numerical modelling using suitable constitutive models. In this context, some constitutive models capable of simulating static liquefaction behaviour of loose saturated sands are reviewed. It is generally concluded that the finite element method can be a helpful tool for modelling stability of tailings dams.

  • 1424.
    Zardari, Muhammad Auchar
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mattsson, Hans
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    3D finite element analyses of a corner at Aitik tailings dam in Sweden2012Ingår i: SWEMP 2012: International symposium on Environmental Issues and Waste Management in Energy and Mineral Production, 2012, s. 444-452Konferensbidrag (Refereegranskat)
    Abstract [en]

    The 3D finite element analyses were performed for the gradual raisings of a corner section of Aitik tailings dam, located in the north of Sweden. The purpose of the analyses was to investigate the potential risk of low compressive stresses or tensile stresses in the corner and to evaluate the slope stability of the dam for current and future raisings. The results indicate that the magnitudes of the minor effective principal stresses in the interior of the dam are sufficient to resist the development of soft zones or cracks in the dam and it is interpreted that there is no increased risk of internal erosion. The slope stability analyses show that the dam has enough safety up to a height of 76 m, if the dam is gradually strengthened with rockfill supports on the downstream side.

  • 1425.
    Zardari, Muhammad Auchar
    et al.
    Quaid-e-AwamUniversity of Engineering, Science and Technology, Nawabshah.
    Mattsson, Hans
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Ormann, Linda
    Fortum, Power Division, Renewable Energy, Våxnäsgatan 10, Box 2087, SE-65002 Karlstad, 8 Sweden.
    Comparison of three-dimensional and two-dimensional axisymmetric finite element analyses of a corner section of a tailings dam2017Ingår i: Scientia Iranica. International Journal of Science and Technology, ISSN 1026-3098, E-ISSN 2345-3605, Vol. 24, nr 5, s. 2320-2331, artikel-id 9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents three dimensional (3D) and two dimensional (2D) axisymmetric finite element analyses of a corner of a tailings dam. The analyses were performed to: (i) locate tension and/or low compression zones and to evaluate slope stability during sequential raising of the dam corner, and (ii) find whether the results of 2D axisymmetric analyses can be reliable for the dam corner. The corner is a potentially weak section of the dam where tension and/or low compression zones may develop. Development of such zones inside the dam corner can lead to cracks and initiation of internal erosion. The results of both the 3D and 2D axisymmetric analyses indicated that (i) tension and/or low compression zones were located in vicinity of surface of the dam corner mainly above the phreatic level, and (ii) the dam corner is stable up to the planned height if it is gradually strengthened with rockfill berms on the downstream side. The results of 2D axisymmetric analyses showed a fairly good agreement with those of 3D analyses. It is concluded that 2D axisymmetric analyses are appropriate for this dam corner. This implies that significant computational time can be saved by utilizing 2D analyses instead of 3D analyses.

  • 1426.
    Zardari, Muhammad Auchar
    et al.
    Department of Civil Engineering, MUET.
    Ormann, Linda
    Dam Safety Forum, Power Division Renewable Energy.
    Mattsson, Hans
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Numerical Analysis of Staged Construction of an Upstream Tailings Dam2014Ingår i: Proceedings of 1st National Conference on Civil Engineering (NCCE 2013-14): (Modern Trends and Advancements), Quest Nawabshah, Pakistan: Department of Civil Engineering, Quest Nawabshah, Pakistan , 2014, s. 150-160Konferensbidrag (Refereegranskat)
    Abstract [en]

    A case study is presented in this paper which describes finite element analysis of staged construction of the upstream tailings dam Aitik, located in north of Sweden. The purpose of the study is to evaluate stability of the dam for current and future raisings and to strengthen the dam with optimum volume of rockfill banks on the downstream side when stability of the dam is not satisfactory during a construction stage. The finite element method was utilized to model the consolidation process and stability of the dam during the staged construction. The study has shown that stability of the dam during raisings was reduced due to build-up of excess pore pressures. Therefore, the dam was strengthened with rockfill banks on the downstream side to carry out the construction of the dam at a planned rate of raising. An optimization analysis was performed in order to reduce the volume of the rockfill necessary for stabilizing the dam. With the use of the finite element based optimization approach discussed in this paper, stability of the dams during staged construction can be enhanced by utilizing a minimum volume of rockfill banks.

  • 1427.
    Zeinali, Amin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Thaw Mechanism in Subgrades2018Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Freezing-thawing, changes the properties of soil due to the phase change of the water in the soil body. Freezing-thawing cycles in the soil have been studied for several decades including extensive laboratory research. In this study, the main focus is thawing based on laboratory investigation. The soil used in the laboratory study is taken from a minor road where an additional field study has been carried out.

    A freezing-thawing laboratory apparatus is manufactured and used in order to get better understanding of the freezing-thawing process. The apparatus is designed for cylindrical sample, one dimensional heat flow, freezing/thawing from top to bottom, water supply from bottom (access to external water) and possible to apply overburden load.

    he laboratory tests were conducted at similar soil samples at different boundary conditions. Water is liberated in the thawing zone of the sample. During thawing the only drainage path is to the surface, however, water migrates upwards even when entire soil is thawed. Upwards water migration after thawing period can be due to the changes in thawed soil properties such as permeability and fine particles redistribution. The rate of thawing is a very important factor for thawing conditions. At low thawing rate the drainage capacity of sample is sufficient to drain the liberated water from ice. Moreover, freezing condition i.e. access to water, has high impact on thawing process. If the volume of ice lenses is high,the thawed soil fluidizes as the water migrates upwards. Pore pressure transducers will be added to the apparatus for further investigation regarding both freezing and thawing.

    The field study has been conducted in order to study thaw behavior in low volume road embankment. The scope of the study is to investigate the thaw weakening progress by Falling Weight Deflectometer (FWD) and Dynamic Cone Penetration (DCP) tests on low volume embankment road near Luleå,northern Sweden. The results from methods is compared and the differences in how they are capturing the thawing is discussed. DCP which is known as an easy and cheap method to estimate stiffness of soil layers is applied to estimate thawing period and the layer which thaw weakening takes place at. Stiffness gained by back calculation of FWD results which is performed on the same road embankment and same period of time DCP test is done.

  • 1428.
    Zeinali, Amin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Dagli, Deniz
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Edeskär, Tommy
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Freezing-Thawing Laboratory Testing of Frost Susceptible Soils2016Ingår i: Proceedings of Nordic Conference on Soil Mechanics and Geotechnical NGM: Reykjavik, Iceland 25th – 28th of May 2016, 2016, s. 267-276Konferensbidrag (Refereegranskat)
    Abstract [en]

    Frost heave and thaw weakening are two common concerns in designing and constructing roads throughout cold region areas. Cold regions can be defined in terms of air temperature and frost penetration by frozen ground engineering. Researchers have been studying frost action in soil for the past 85 years in order to design ways to reduce the costly damage to roads. Conducting the test on frost-susceptible soil must be done in order to retrieve data for frost heave and thaw weakening modeling in the soil body during a certain freezing-thawing cycle. This paper reviews and discusses the apparatuses used for this purposes. The studied apparatuses are cylindrical and provide heat through one dimension. The studied apparatuses mostly differ in the diameter and length of their cylindrical cell; likewise, temperature gradients differ from one apparatus toanother. In this study the LTU’s apparatus which was primarily designed to investigate the research related questions concerning freezing and thawing phenomena is presented in detail. The theory of segregation potential is applied for evaluation of the frost heave test and the thaw consolidation theory is applied for the thaw test. The main goal of the project is to conduct a series of experimental tests on various types of soil while exposing them to frost action in the apparatus to propose a classification system for the different types of soil in question with respect to their susceptibility to the frost action phenomena.

  • 1429.
    Zeinali, Amin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Edeskär, Tommy
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Laue, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mechanism of thawing2020Ingår i: Cogent Engineering, E-ISSN 2331-1916, Vol. 7, nr 1, artikel-id 1716438Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Freezing–thawing phenomena have been studied at laboratory scale for decades with various techniques and test setups. In this study, a freezing–thawing laboratory apparatus was supplemented with a camera in order to get a better understanding of ice formation during the freezing period and ice melting during the thawing period. The results from three thawing tests with identical samples but different boundary conditions are presented here. Water intends to migrate upward even when the entire frozen part has been thawed. That would cause excess pore water pressure and softening of the soil after the thawing period as well. Upward water migration after the thawing period is due to changes in thawed soil properties such as permeability and fine particle redistribution. The rate at which thawing takes place is a very important factor for thawing conditions. Moreover, freezing condition, i.e. access to water, has a high impact on thawing soil. If the volume of ice lenses is sufficient, frozen soil would fluidize during thawing.

  • 1430.
    Zhang, Juanrong
    et al.
    College of Civil Engineering, Zhengzhou University.
    Guo, Lijie
    Beijing General Research Institute of Mining and Metallurgy.
    Sun, Xiaoxiao
    College of Civil Engineering, Zhengzhou University.
    Li, Wenchen
    Beijing General Research Institute of Mining and Metallurgy.
    Jia, Qi
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Study on the Strength Development of Cemented Backfill Body from Lead-Zinc Mine Tailings with Sulphide2018Ingår i: Advances in Materials Science and Engineering, ISSN 1687-8434, E-ISSN 1687-8442, Vol. 2018, artikel-id 7278014Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The unconfined compressive strength (UCS) development of cemented backfill materials for lead-zinc mine tailings with sulphide was studied. The results showed that the UCS of the cemented backfill body with ordinary Portland cement (OPC) as binder decreased in the later curing days, regardless of particle size. Under the same conditions, the higher the OPC content, the higher the UCS of the cemented backfill body, and the UCS of the cemented backfill body began to decrease at the longer curing days. Under the same conditions, the finer the tailings, the lower the UCS of the cemented backfill body at each age, and the UCS of the cemented backfill body began to decrease at the earlier curing age. X-ray diffraction analysis (XRD) showed that the reduction of the UCS of the cemented backfill body was related to the formation of an expansive substance (expansive gypsum) in the cemented backfill body, which led to the cracking of the test sample. In the cemented backfill materials of coarse tailings of lead-zinc mine, the composite binder formed by OPC and calcined kaolin (CK) containing metakaolin was used; the amount of calcium hydroxide, the hydration product of cement, was reduced or eliminated due to the pozzolanic reaction of metakaolin; and the amount of expansive gypsum was reduced or eliminated, so the UCS of the cemented backfill body increased within 360 days of curing.

  • 1431.
    Zhang, Ping
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    A 3DEC numerical analysis of the interaction between uneven rock surface and shotcrete lining: Validation of physical model and evaluation of influence of unevenness on the support effect of shotcrete2013Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Although shotcrete (sprayed concrete) has been widely used as rock support in mines and in civil engineering projects, the complex interaction between shotcrete and rock has not been studied well. The main reason is that the performance of shotcrete is influenced by a number of important parameters.Experiences from previous research and past projects show that the unevenness of rock surface has a large impact on the number of failures at the interface and in the lining. Furthermore, the behaviour of the lining is sensitive to small amplitudes of the surface roughness. Although people have done some experimental and numerical analysis, the influence of the complex unevenness of three dimensional shaped surfaces on the shotcrete – rock interaction has not been well studied.The project here focuses on the influence of the surface unevenness of a circular opening on the support effect of shotcrete. The work was done by using a 3D numerical simulation (3DEC) and was conducted in two stages. In stage 1, the numerical model was validated by comparing with physical model tests by Chang (1994). In stage 2, based on the well validated numerical model, the influence of unevenness on the support effect of shotcrete was further investigated.

  • 1432.
    Zhang, Ping
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Dineva, Savka
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Hansen-Haug, Jouni
    Lundin Mining.
    Woldemedhin, Biruk
    LKAB.
    Töyrä, Jimmy
    LKAB.
    Boskovic, Mirjana
    LKAB.
    Nyström, Anders
    Boliden.
    Marklund, Per-Ivar
    Boliden.
    Mozaffari, Shahram
    Boliden.
    Establishment of experimental sites in three Swedish mines to monitor the in-situ performance of ground support systems associated with mining-induced seismicity2016Ingår i: Proceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction / [ed] E . N ordlund, T.H. Jones and A. Eitzenberger (eds), 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to assess the performance of ground support components and systems when subjected to seismic activity and strong ground motion, Luleå University of Technology together with three Swedish mining companies (Lundin Mining, LKAB and Boliden) started a three year research project in September 2014. The aim of the project is to develop new methods for evaluating the rock support performance in-situ that use all available information about i) the source of the seismic event (obtained from the seismic network in the mine and additional seismic sensors), ii) seismic loading (ground motion) recorded by temporary local seismic networks, and iii) the consequences of the seismic loading in terms of damage to the underground excavations and the rock support.The sites with high potential of seismic damage were defined after the historical damaging seismic events were reviewed and the mining-induced stress disturbance was investigated with 3D numerical models. As of 31 December 2015, four sites in three different mines have been instrumented. Geophones (in depth and at surface), multi-points extensometers and instrumented bolts were installed to monitor the ground motion, the deformation of the rock mass and the elongation of the bolts. Observation boreholes were drilled to investigate the rock lithology, structures as well as fracture distribution and development. The data from locally installed geophones will be integrated with seismic data recorded by the mine-wide network. For each monitoring point, all of the instruments and observation boreholes were located at very close area within 0.5-1 m distance from each other. These results will be used to establish the relationship between the dynamic loading and the response of rock mass and rock bolts. Additionally, laser scanning is used to measure the surface deformation of the whole volume of instrumented sites with time. Two damaging seismic events occurred near the instrumented sites after the instruments were installed and the results of site investigation show that installed instruments have captured the response of the rock mass and bolts due to production blasting and seismic events.

  • 1433. Zhang, Ping
    et al.
    Li, Ning
    Xi'an University of Technology.
    Li, Xibing
    School of Resources and Safety Engineering, Central South University, Changsha.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Compressive failure model for brittle rocks by shear faulting and its evolution of strength components2009Ingår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 46, nr 5, s. 830-841Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A physical theory for brittle failure is presented that aims to explain both the phenomenological and micro-structural observations. The objective of this model is to capture the important attributes inferred from micro-structural experiments so as to arrive at constitutive relations that describe macroscopic failure behaviour. Based on experimental results, the micromechanical failure character- isation is summarised first. The localised failure process of rock will experience two stages: the brittle breakage stage (bond rupture of rock bridge) and the sliding stage (frictional resistance of failure plane mobilisation). A physical model is developed by dividing the sample into elastic and localised shear zones. Furthermore, the deformation process of the localised shear zone is divided into bond loss and frictional resistance mobilisation in two stages. To combine the micro-characteristics with the macromechanical properties, the chain models in localised shear zone, and the homogenisation method are adopted. The model is validated against the experimental data of Yumlu and Ozbay's. Subsequently, the localised progressive failure characteristics of rock are analysed by changing the model's parameters. The intrinsic effects and influential factors such as geometrical effects (size effect, shape effect), the strain softening phenomenon and Class II stress-strain curves are revealed. Finally, in order to be used easily by engineers, the simplified description of rock failure process and its evolution of strength components are given based on the model.

  • 1434.
    Zhang, Ping
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mikromechanical modeling of fire-induced thermal damae in a laboratory model tunnel2015Konferensbidrag (Övrigt vetenskapligt)
  • 1435.
    Zhang, Ping
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mainali, Ganesh
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, Christine
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Jansson, Robert
    SP Sveriges Tekniska Forskningsinstitut.
    Experimental study of thermal spalling on rock blocks exposed to different fire/heating conditions2011Ingår i: Bergmekanikdag 2011: Föredrag, Stiftelsen bergteknisk forskning - Befo , 2011, s. 53-63Konferensbidrag (Övrigt vetenskapligt)
  • 1436.
    Zhang, Ping
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mainali, Ganesh
    Saiang, Christine
    Jansson, Robert
    SP Technical Research Institute of Sweden.
    Adl-Zarrabi, Bijan
    SP Technical Research Institute of Sweden.
    Experimental study on thermal spalling of rock blocks exposed to fire2010Ingår i: Bergmekanikk i Norden 2010 = Rock mechanics in the Nordic countries 2010 / [ed] Charlie C. Li, Kongsberg, Norway, 9.-12. June 2010, 2010, s. 294-305Konferensbidrag (Refereegranskat)
  • 1437.
    Zhang, Ping
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Swan, Graham
    Rock Mechanics and Mine Design, Sudbury, Canada.
    Yi, Changping
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Velocity Amplification of Seismic Waves Through Parallel Fractures Near a Free Surface in Fractured Rock: A Theoretical Study2019Ingår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 52, nr 1, s. 199-213Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To determine the dynamic demand for support design under rockburst conditions, one of the most important issues is the prediction of ground motion parameters at the site of interest. Field monitoring has shown that the peak ground motion at the surface of an excavation in fractured rock is preferentially amplified compared to the motion in solid rock at a similar distance from the source. However, the traditional scaling laws used in rock support design do not account for the effect of free surface (excavation) and fracturing of rock. Recent studies have shown that high ground motion might be generated when a seismic wave crosses through fractures near a free surface in fractured rocks which is very complex and is not well understood. In this paper, particle velocity amplification was theoretically studied by investigating the dynamic interaction between seismic wave and multiple fractures near a free surface using the method of characteristics and the displacement discontinuity model. A harmonic load was applied on a model with a fractured zone near a free surface to investigate this phenomenon. After the harmonic wave propagated normally through multiple parallel fractures, the velocity amplification factor (VAF) was calculated as a function of the ratio of the magnitude of the peak particle velocity at the free surface of the model to the peak input velocity. The VAF can be as high as 3.77 and varies depending on the state of the fractured rock and the characteristics of the seismic wave. Parameter studies were conducted to investigate the effects of seismic load and multiple fractures on wave propagation, especially in terms of the wave frequency, the fracture spacing, the number of fractures and the stiffness of fractures. The results have proved that the interaction of the seismic wave and multiple fractures near the free surface strongly influences the ground motion. Quantitative relationships between the various influential factors and the corresponding VAF were developed. It is anticipated that such relationships can provide criteria to improve the current design procedures and help mining engineers to improve their rock support practice for rockburst-prone areas.

  • 1438.
    Zhang, Ping
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Swan, Graham
    Rock Mechanics and Mine Design, Canada.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    1D numerical simulation of velocity amplification of P-waves travelling through fractured rock near a free surface2015Ingår i: The Southern African Journal of Mining and Metallurgy, ISSN 2225-6253, E-ISSN 1543-9518, Vol. 115, nr 11, s. 1121-1126Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The most widely used support design damage criterion for rockburst-prone mines is based upon kinetic energy, which is proportional to the square of the ejection velocity and is commonly expressed in terms of peak particle velocity (PPV). Field monitoring and back-analyses have shown that ejection velocities of the order of 10 m/s and higher can result from seismic events of moderate magnitude. Such velocities are much higher than those predicted using PPV obtained from scaling laws. It has also been found that the peak ground motion (i.e. PPV) on the surface of an excavation is preferentially amplified (by four-to tenfold) compared to the motion in solid rock at a similar distance from the source. However, the wave propagation and interaction processes involved within the fractured rock in generating high ground motion are very complex and are not well understood at this time. In this paper, velocity amplification was investigated by modelling the dynamic interaction between fractured rock and a free surface using a 2D discontinuum-based numerical program, UDEC (Universal Distinct Element Code). A 1D model with a fractured zone was used to represent the fractured rock. Velocity amplification, quantified by PPV, predicted at the free end of the model was 2.0-3.6 times higher than the input velocity. It was found that the wave frequency, fracture stiffness, fracture spacing, and thickness of fractured zone are the main factors that affect the velocity amplification. The results have proved that the interaction of the seismic wave and multiple fractures near the free surface strongly influences the ground motion

  • 1439.
    Zhang, Ping
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Yi, Changping
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Shirzadegan, Shahin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nyberg, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Malmgren, Lars
    Mining Technology R and D, LKAB Kiruna Mine.
    Nordqvist, Anders
    LKAB.
    Numerical back-analysis of simulated rockburst field tests by using coupled numerical technique2013Ingår i: Ground Support 2013: Proceedings of the Seventh International Symposium on Ground Support in Mining and Underground Construction / [ed] Yves Potvin; B.G.H. Brady, Perth, Australia: Australian Center for Geomechanics , 2013, s. 565-581Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to assess the capacity of ground support systems when submitted to dynamic loading, simulated rockburst tests utilizing blasting have been performed for many years in different countries with limited success. In general, the blasts need to be carefully designed in order to reach the goal; however, different blast layouts (e.g. blasthole angle, burden) have been used based on researcher’s experience without conducting detailed analyses, the exception being a field test by CSIR. Recently, field trials have been conducted at the LKAB Kiirunavaara underground mine with some unexpected results which show that either the whole tested panel was destroyed or only a few fractures were formed without any ejections being observed. The aim of this paper is to investigate the failure mechanism in the simulated rockburst tests and improve the blast design by back-analyzing the test results using a coupled numerical modeling technique. The blast was simulated by using finite element method (LS-DYNA) and the dynamic interaction between the blasting generated waves and the opening was simulated by using discrete element modeling (UDEC) with the dynamic input from LS-DYNA. The numerical modeling showed that blasting can create both radial fractures radiating from the blasthole and fractures parallel or sub-parallel to the surface of the tested panel caused by reflected tensile stress waves. By comparing the results of the numerical modeling with the measured data, it is shown that the collapse failure was mainly controlled by the creation of a cone-shaped area formed by radial fractures and the burden seems to be a critical factor. In order to obtain fractures caused by reflected tensile stress waves and reduce blasting induced radial fractures, 2 parallel blastholes are suggested with larger burden (> 5 m) for future tests. Furthermore, the limitation of the current numerical modeling has also been discussed. The coupled numerical technique has shown its advantage when simulating blasting as well as interaction between waves and opening and it can thus be used as a tool for extrapolating results from simulated rockburst experiments if detailed geological structure and ground support system can be incorporated in the model and the model can be well calibrated.

  • 1440. Zhang, Ping
    et al.
    Yin, J.J.
    Hunan University.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Li, N.
    Xi'an University of Technology.
    Determination and verification of the longitudinal deformation profile in a horse-shoe shaped tunnel using two-stage excavation2008Ingår i: MassMin 2008: Proceedings of the 5th International Conference and Exhibition on Mass Mining, Lulea, Sweden 9-11 June 2008 / [ed] Håkan Schunnesson; Erling Nordlund, Luleå: Luleå tekniska universitet, 2008, s. 845-854Konferensbidrag (Refereegranskat)
  • 1441.
    Zhang, Z. X.
    et al.
    Luleå tekniska universitet.
    Kou, S. Q.
    Luleå tekniska universitet.
    Jiang, L. G.
    University of Science and Technology, Beijing.
    Lindqvist, Per-Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Effects of loading rate on rock fracture: fracture characteristics and energy partitioning2000Ingår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 37, nr 5, s. 745-762Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By means of the Scanning Electron Microscope (SEM), an examination was performed of the fracture surfaces (including their vertical sections) of both Fangshan gabbro and Fangshan marble specimens fractured at the loading rates k = 10-2 ≈ 106 MPa m1/2 s-1. The results showed that one or more branching cracks near the fracture surfaces of dynamic rock specimens were clear and the cracks increased with increasing loading rates. However, such branching cracks were rarely seen near the static fracture surfaces. In addition, with the aid of the Split Hopkinson Pressure Bar (SHPB) testing system and a high-speed framing camera, the energy partitioning in the dynamic fracture process of a short rod (SR) rock specimen was analysed quantitatively. The total energy WL absorbed by an SR specimen in the dynamic fracture process mainly consisted of the fracture and damage energy WFD and the kinetic energy WK of flying fragments. The energies WL and WK could be quantitatively calculated through stress wave measurement and high-speed photography in the SHPB testing system. Thus, the fracture and damage energy WFD could be obtained. The results showed that: (1) the energy WK increased with an increase in the impact speed of the striker bar or the loading rate; (2) the energy WFD for dynamic rock fracture was markedly greater than that for static rock fracture, and the WFD increased with an increase in the impact speed of the striker bar or the loading rate; and (3) the value WL/WB (WB is the energy input into the loading system) in the case of dynamic fracture is much lower than that in the case of static fracture. In addition, the ratio decreases with an increase in the loading rate or the impact speed of the striker bar. This means that the energy utilisation decreases when the loading rate or the impact speed of the striker bar rises. Finally, some application problems are discussed in the paper.

  • 1442.
    Zhang, Z X
    et al.
    Luleå tekniska universitet.
    Kou, S Q
    Luleå tekniska universitet.
    Lindqvist, Per-Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Measurements of cutter forces and cutter temperature of boring machine in Äspö Hard Rock Laboratory2001Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    I denna rapport presenteras både testmetoder och resultat från mätning av verktygskrafter och temperatur under fullborrning av schakt i Äspölaboratoriet.För att bedöma deformationer som induceras i axlarna på verktygen (cutters) och för rätt val av kraftgivare genomfördes numeriska beräkningar. Dessa visade att vanliga trådtöjningsgivare kunde användas. Ett system med oberoende belastning i tre riktningar för kalibrering i laboratorium av kraftgivare monterades för att lösa problemet med koppling mellan givare under fältmätningen. Med hjälp av det därpå utvecklade mätsystemet, som testades i laboratorium, mättes normalkraft, tangentiell kraft och sidokraft på två verktyg i fält. Dessutom mättes temperaturen i axeln på ett av verktygen i fronten på borrhuvudet. Efter mätning av verktygskrafter och temperatur, uttogs borrkärnor från botten och väggar på det schakt som borrats. Proverna sågades, polerades och undersöktes i svepelektronmikroskop. Längden på sprickor som uppstått under verktygen mättes och ett approximativt samband mellan längden på mediansprickor och relevanta verktygskrafter kunde skapas. Detta samband jämfördes med teoretiska samband som etablerats tidigare. Slutligen kunde, utgående från de erhållna resultaten, den spruckna zonen omkring schaktet beskrivas. Resultaten visar att: (1) två olika sprickzoner kan utskiljas: en i väggarna och en i botten på schaktet. Djupet på den uppspruckna zonen i botten är mycket större än i väggarna på schaktet beroende på att den maximala normalkraften på verktyg riktat framåt (front cutter) alltid är mycket högre än på verktyget mot väggen (gauge cutter). (2) Varje sprickzon inkluderar dels en kraftigt uppsprucken zon dels glest liggande, långa mediansprickor. (3) Från mätningen av fyra bergprover har maximala djupet på mediansprickor i schaktbotten uppmätts till 27,1 mm och maximala djupet på den kraftigt uppspruckna zonen till 2,5-3,0 mm.

  • 1443. Zhang, Z. X.
    et al.
    Kou, S. Q.
    Yu, J
    Yu, Y
    Jiang, L. G.
    Lindqvist, Per-Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Effects of loading rate on rock fracture1999Ingår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 36, nr 5, s. 597-611Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By means of a wedge loading applied to a short-rod rock fracture specimen tested with the MTS 810 or SHPB (split Hopkinson pressure bar), the fracture toughness of Fangshan gabbro and Fangshan marble was measured over a wide range of loading rates, =10−2–106 MPa m1/2 s−1. In order to determine the dynamic fracture toughness of the rock as exactly as possible, the dynamic Moiré method and strain–gauge method were used in determining the critical time of dynamic fracture. The testing results indicated that the critical time was generally shorter than the transmitted wave peak time, and the differences between the two times had a weak increasing tendency with loading rates. The experimental results for rock fracture showed that the static fracture toughness KIc of the rock was nearly a constant, but the dynamic fracture toughness KId of the rock (≥104 MPa m1/2 s−1) increased with the loading rate, i.e. log(KId)=a log +b. Macroobservations for fractured rock specimens indicated that, in the section (which was perpendicular to the fracture surface) of a specimen loaded by a dynamic load, there was clear crack branching or bifurcation, and the higher the loading rate was, the more branching cracks occurred. Furthermore, at very high loading rates (≥106 MPa m1/2 s−1) the rock specimen was broken into several fragments rather than only two halves. However, for a statically fractured specimen there was hardly any crack branching. Finally, some applications of this investigation in engineering practice are discussed.

  • 1444.
    Zhang, Z X
    et al.
    Luleå tekniska universitet.
    Yu, J
    University of Science and Technology, Beijing.
    Kou, S.Q.
    Luleå tekniska universitet.
    Lindqvist, Per-Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Effects of high temperatures on dynamic rock fracture2001Ingår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 38, nr 2, s. 211-225Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dynamic fracture toughness of Fangshan Gabbro and Fangshan Marble subjected to high temperature was measured by means of the split Hopkinson pressure bar (SHPB) system. The specimens for measuring the fracture toughness were manufactured according to the requirements for the Short Rod (SR) specimen suggested by ISRM. Two cases were investigated: (1) the SR specimens of the gabbro and marble were fractured at high temperature (100-330 degrees C), and (2) the specimens of the rocks were first pre-heat-treated at 200 degrees C for the marble and 600 degrees C for the gabbro, and then fractured at room temperature. The experimental results showed that under dynamic loading the fracture toughness of both the gabbro and the marble tested in the above-mentioned cases increased with increasing loading rates. The relationship between the fracture toughness and the loading rates in the two cases is similar to that obtained in the room temperature environment, i.e., without high temperature. (This is defined as the third case.) It can be concluded that temperature variation affects the dynamic fracture toughness of the two rocks to a limited extent within the temperature ranges tested. This is different from the results obtained under the static loading condition. Furthermore, by means of the scanning electronic microscope (SEM), the vertical sections of the fracture surfaces for some gabbro specimens were examined. In addition, the fractal dimensions of the fracture surfaces of some specimens were measured by means of fractal geometry. The results showed that under dynamic loading: (1) macro-crack branching near the fracture surfaces was universal; (2) the fractal dimensions increased with increasing loading rates; (3) in the sections of the specimens tested at high temperature there were many micro-cracks that were probably induced by thermal cracking. On the basis of the above macro- and micro-experimental investigation, an energy analysis of the process of dynamic rock fracture was performed. The results showed that the energy utilisation in dynamic fracture was much lower than that in static fracture.

  • 1445.
    Zhang, Zhi-qiang
    et al.
    Xi’an University of Technology, Xi’an, P.R. China.
    Li, Ning
    Xi’an University of Technology, Xi’an, P.R. China.
    Zhang, Ping
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Han, S.
    Xi’an University of Technology, Xi’an, P.R. China.
    Effect of fault on tunnel stability with different distribution2013Ingår i: Global View of Engineering Geology and the Environment: International Symposium & 9th Asian Regional Conference of IAEG / [ed] Faquan Wu; Shengwen Qi, London: CRC Press, Taylor & Francis Group , 2013, s. 279-285Konferensbidrag (Refereegranskat)
    Abstract [en]

    For tunnel engineering, the fault that locates near tunnel always plays an important role on the stability of the surrounding rock mass and the safety of the supporting system. To investigate the influence of the fault on the tunnel stability, systematic numerical experiments are carried out via the FINAL code. Through these numerical experiment results, the displacement and the distribution of the stress in surrounding rock mass are analyzed for these cases of the different locations and dips of fault around tunnel periphery, and the stress in the sprayed concrete layer are analyzed as well. To simulate the characteristics of the fault located in the rock mass, the COJO element, embedded in the FINAL code, is used in all numerical experiments. The quantized results reflecting the rules of the change for the displacement, stress, plastic region in the surrounding rock mass are obtained also in this paper.

  • 1446.
    Zhang, Zongxian
    et al.
    Luleå University of Technology.
    Kou, Shaoquan
    Luleå University of Technology.
    Lindqvist, Per-Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    In-situ measurements of cutter forces on boring machine at Äspö Hard Rock Laboratory. Part 2: Characteristics of cutter forces and examination of cracks generated2003Ingår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 36, nr 1, s. 63-83Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By means of spectral analysis, the measured normal forces, tangential forces, and side forces acting on two button cutters on the boring machine in Äspö Hard Rock Laboratory were analysed and the basic characteristics of the cutter forces were determined. After the measurements of the cutter forces, some rock core samples were taken from the bottom and the wall of the test borehole. These samples were cut, polished, and examined by means of a Scanning Electron Microscope (SEM). The lengths of the major cracks in the rock samples were measured, and a relation between the length of the median cracks and the relevant cutter forces was investigated.

  • 1447.
    Zhang, Zongxian
    et al.
    Luleå University of Technology.
    Kou, Shaoquan
    Luleå University of Technology.
    Lindqvist, Per-Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    In-situ measurements of TBM cutter temperature in Äspö Hard Rock Laboratory, Sweden2001Ingår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 38, nr 4, s. 585-590Artikel i tidskrift (Refereegranskat)
  • 1448.
    Zhang, Zongxian
    et al.
    Luleå University of Technology.
    Kou, Shaoquan
    Luleå University of Technology.
    Tan, Xiangchun
    Luleå University of Technology.
    Lindqvist, Per-Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    In-situ measurements of cutter forces on boring machine at Äspö Hard Rock Laboratory. Part 1: Laboratory calibration and in-situ measurements2003Ingår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 36, nr 1, s. 39-61Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents the testing methods used and the results obtained in an investigation of the cutter forces on a Boretec DS 1.6 boring machine during field boring in Äspö Hard Rock Laboratory. Two button cutters, one front cutter and one gauge cutter, were used in the field measurements. A total of 6 strain gauges were bonded on the shaft of each cutter. And each group of two gauges was used to measure a one-orthogonal cutter force component, i.e. the normal force, tangential force, and side force, respectively. In order to measure the cutter forces successfully, a telemetry system composed of a transmitter and a receiver was employed to transfer the signals from the strain gauges to a computer.A three-direction-loading system was employed in the laboratory calibration so as to solve the force-coupling problem appearing in the cutter force measurements. Correspondingly, a mathematical treatment of the force-coupling problem was performed. Then, by means of the established testing system, which was proved successful in the laboratory, the normal force, tangential force, and side force of the two button cutters on the boring machine were measured in the field. In addition, the penetration rate, thrust, and rotation speed of the boring machine were also recorded in the field. The results show the following. (1) A force-coupling phenomenon really exists and it should be considered. (2) All three directional force components always show quite a high peak value every few seconds. (3) The cutter forces of the front cutter are always much larger than the respective cutter forces of the gauge cutter. Moreover, as expected, the normal force of each cutter is much larger than the tangential force and side force of the cutter in question.

  • 1449.
    Zhang, Zongxian
    et al.
    Luleå University of Technology.
    Yu, J.
    Luleå University of Technology.
    Kou, Shaoquan
    Luleå University of Technology.
    Lindqvist, Per-Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    On study of influences of loading rate on fractal dimensions of fracture surfaces in Gabbro2001Ingår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 34, nr 3, s. 235-242Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Studies of the effects of loading rates on rock fracture were performed for decades. However, the previous work on static or dynamic rock fracture was mainly limited to a macro-experimental study. The present investigation measures the fractal dimensions of the fracture surfaces of the gabbro specimens fractured at various loading rates covering static and dynamic loading, and explores the relationship between the fractal dimensions and the fracture toughness of the rock.

  • 1450.
    Zhang, Z.X.
    et al.
    Luleå tekniska universitet.
    Kou, S.Q.
    Luleå tekniska universitet.
    Lindqvist, Per-Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Fracture behaviour of rock under dynamic loading1999Ingår i: Comptes-rendus / 9 Congrès international de mécanique de roches, Paris, France 1999 / [ed] Gerard Vouille; Pierre Berest, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1999, Vol. 2, s. 1127-1130Konferensbidrag (Refereegranskat)
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