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  • 1.
    Elhami, Ehsan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    2D modeling of the Kristineberg mine stope2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Mining operations at the Kristineberg Mine approaches depths of more than 1300 m. Severe ground conditions are consequently expected due to the combination of weak rock formations and relatively high in-situ stresses. The required support techniques, however, are not unique and depend on the ground deformation characteristics. On the other hand, the complex geology of the mining zone induces different types and magnitudes of failures. As a result, to improve the support performance, the possible ground conditions which may arise from varieties of geological parameters at the mine need to be characterized. Among different geological parameters at the mine, the location of the rock formations is seen to be an important factor, influencing the deformation behavior of the rock mass. The aim of this study is to increase the understanding of how the rock mass behavior changes due to the location of the rock formations. The study is performed through numerical modeling of an unsupported stope using FLAC2D; the required input data are determined based on the field observations and the corresponding literatures. Then, the modeled deformation behavior of the stope is studied through “Parameter Analysis”. The results, which show the sensitivity of the ground deformation to the location of the surrounding rock formations, can be used in future support design analysis.

  • 2.
    Idris, Musa Adebayo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Comparison of different probabilistic methods for analyzing stability of underground rock excavations2016Inngår i: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 21, nr 21, s. 6555-6585Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stability analyses of underground rock excavations are often performed using traditional deterministic methods. In deterministic methods the mean or characteristics values of the input parameters are used for the analyses. These method neglect the inherent variability of the rock mass properties in the analyses and the results could be misleading. Therefore, for a realistic stability analyses probabilistic methods, which consider the inherent variability of the rock mass properties, are considered appropriate. A number of probabilistic methods, each based on different theories and assumptions have been developed for the analysis of geotechnical problems. Geotechnical engineers must therefore choose appropriate probabilistic method to achieve a specific objective while taking into account simplicity, accuracy and time efficiency. In this study finite difference method was combined with five different probabilistic methods to analyze the stability of an underground rock excavation. The probabilistic methods considered were the Point Estimate Method (PEM), the Response Surface Method (RSM), the Artificial Neural Network (ANN), the Monte Carlos Simulation (MCS), and the Strength Classification Method (SCM). The results and the relative merits of the methods were compared. Also the general advantages of the probabilistic method over the deterministic method were discussed. Though the methods presented in this study are not exhaustive, the results of this study will assist in the choice of appropriate probabilistic methods for the analysis of underground rock excavations. 

  • 3.
    Idris, Musa Adebayo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Consideration of the rock mass property variability in numerical modelling of open stope stability2012Inngår i: Föredrag vid Bergmekanikdag i Stockholm, 12 mars 2012, Stockholm: Stiftelsen bergteknisk forskning - Befo , 2012, s. 111-123Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    This paper presents a probabilistic approach for modelling complex rock masses wherethe intrinsic properties are highly variable. For this study a complex orebody in aCanadian mine is used. The mechanical properties of the host rock and the ore in thismine are found to be intrinsically variable with high contrast between their mechanicalproperties. It is apparent that the use of traditional deterministic methods to study thebehaviour of the open stopes is not appropriate for this mine. Hence, in this study aprobabilistic approach is adopted which allows the propagation of the variability of theinput parameters in the numerical modelling. Three different approaches were used toanalyze the stability of the open stopes based on the distribution of the different materialproperties of the rock mass. The results of the analysis using the three methods werecompared and the limitations and the potentials of each of the methods were discussed.The study provides insight into the significance of the rock mass property variability inthe numerical modelling of open stope stability and different ways that it could beincorporated into the modelling.

  • 4.
    Idris, Musa Adebayo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Numerical analyses of the effects of rock Mass property variability on open stope stability2011Inngår i: 45th US Rock Mechanics /Geomechanics Symposium, San Francisco, CA, USA: ARMA, American Rock Mechanics Association , 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The rock mass is intrinsically variable in its physical and mechanical properties which makes it complex. This complexity is evident from the spatial random distribution of the properties from any site characterization program. The precise values for these properties are never known in most cases hence most geotechnical mine designs are based on fixed or discrete values of rock mass properties for stability analysis. This traditional deterministic approach neither reflects the inherent variability nor the uncertainty in the rock mass properties. Therefore, it is desirable to utilize a probabilistic approach which provides a range of possible results based on the variability in the rock mass properties. Understanding the effect of this random distribution and variability of the properties on stope stability is essential for more realistic mine design. In this study, a series of numerical analyses using the explicit finite difference element code FLAC, have been conducted to study the effect of the random distribution and variability of rock mass properties on the stope stability. The rock mass in the FLAC model is represented by different material properties randomly distributed to each zone. In order to compare the results, fixed average values of the material properties were also used for the FLAC model in another simulation. The results clearly indicate that rock mass property variability does affect the stope stability and that a deterministic approach to stope stability analysis could lead to conservative results.

  • 5.
    Idris, Musa Adebayo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Probabilistic analysis of open stope stability using numerical modelling2011Inngår i: International Journal of Mining and Mineral Engineering, ISSN 1754-890X, E-ISSN 1754-8918, Vol. 3, nr 3, s. 194-219Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A probabilistic approach is presented for the analysis of open stopestability. The approach considers the inherent variability and uncertainty whichare typical of rock mass properties. In this study, a series of numerical analyseswere performed using FLAC to study the stability of open stopes while takinginto account the variability in the rock mass properties. The rock mass wasdivided into six strength classes: three classes for the host rock and threeclasses for the massive sulphide ore. Each class was randomly distributed to theelements in the FLAC model. The host rock-to-massive sulphide ore ratio isenvisaged to have a strong influence on the stope. To verify this, three casesof different ore percentages were considered and the results compared.The results, which were presented as Probability Density Functions (PDFs),indicate that the zones of low stiffness show high range of displacements andthat the increase in the percentage of the ore significantly affects the stability ofthe stopes.

  • 6.
    Idris, Musa Adebayo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Stochastic assessment of pillar stability at Laisvall mine using Artificial Neural Network2015Inngår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 49, s. 307-319Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stability analyses of any excavations within the rock mass require reliable geotechnical input parameters such as in situ stress field, rock mass strength and deformation modulus. These parameters are intrinsically uncertain and their precise values are never known, hence, their variability must be properly accounted for in the stability analyses. Traditional deterministic approaches do not quantitatively consider these uncertainties and variability in the input parameters. To incorporate these variability and uncertainties stochastic approaches are generally used. In this study, a stochastic assessment of pillar stability using Artificial Neural Network (ANN) is presented. The variability and uncertainty in the rock mass properties at the Laisvall mine were quantified and the probability density function of the deformation modulus of the rock mass was determined using probabilistic approach. The variability of the in situ stress was also considered. The random values of the deformation modulus and the horizontal in situ stresses were used as input parameters in the FLAC3D numerical simulations to determine the axial strain in the pillar. ANN model was developed to approximate an implicit relationship between the deformation modulus, horizontal in situ stresses and the axial strain occurring in pillar due to mining activities. The closed-form relationship generated from the trained ANN model, together with the maximum strain that the pillar can withstand was used to assess the stability of the pillar in terms of reliability index and probability of failure. The results from this study indicate that, the thickness of the overburden and pillar dimension have a substantial effect on the probability of failure and reliability index. Also shown is the significant influence of coefficient of variation (COV) of the random variables on the pillar stability. The approach presented in this study can be used to determine the optimal pillar dimensions based on the minimum acceptable risk of pillar failure

  • 7.
    Malmgren, Lars
    et al.
    Mining Technology R and D, LKAB Kiruna Mine.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Töyrä, Jimmy
    Bodare, A.
    Division of Soil and Rock Mechanics, Royal Institute of Technology, Stockholm.
    The excavation disturbed zone (EDZ) at Kiirunavaara mine, Sweden: by seismic measurements2007Inngår i: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 61, nr 1, s. 1-15Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The presence of an excavation disturbed zone (EDZ) around an excavation boundary can significantly affect the overall performance of the excavation and the general safety of men and equipment. Hence, it has been an important subject of research in various rock excavation projects. The EDZ is generally defined as the rock zone beyond the excavation boundary where the physical, mechanical and hydraulic properties of the rock have been significantly affected due to the excavation and redistribution of stresses. For LKAB's Kiirunavaara underground iron ore mine in Sweden, the understanding of the EDZ is essential for optimal design of rock support. With this main objective an EDZ investigation was conducted at the mine using seismic measurement techniques. Cross-hole seismics and spectral analyses of surfaces waves (SASW) were the main techniques used. Borehole Image Processing Systems (BIPS) complemented the seismic measurements. The results show that an EDZ with a thickness of 0.5–1. 0 m existed behind the boundaries of the mining drifts being investigated. The magnitude of the Young's modulus of this zone was 50% to 90% of that of the undisturbed rock.

  • 8.
    Mertuszka, P.
    et al.
    KGHM CUPRUM Ltd. Research and Development Centre, Wrocław, Poland.
    Szumny, M.
    KGHM CUPRUM Ltd. Research and Development Centre, Wrocław, Poland.
    Wawryszewicz, A.
    KGHM Polska Miedź S.A., Polkowice-Sieroszowice Mine, Kaźmierzów, Polkowice, Poland.
    Fuławka, K.
    KGHM CUPRUM Ltd. Research and Development Centre, Wrocław, Poland.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Blasting delay pattern development in the light of rockburst prevention: Case study from polish copper mine2019Inngår i: E3S Web of Conferences: IVth International Innovative Mining Symposium / [ed] M. Tyulenev, S. Zhironkin, A. Khoreshok, S. Vöth, M. Cehlár, D. Nuray, J. Janocko, S. Anyona, Y. Tan, A. Abay, D. Marasová and P. Stefanek, EDP Sciences, 2019, Vol. 105, artikkel-id 01012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In order to reduce the risk of induced seismicity related to underground mining, a number of preventive actions are applied in the form of passive and active prevention methods. The former are mainly of an organisational nature and their effectiveness is usually considered in the long term, while the active methods are mostly based on the detonation of explosives and are aimed to release the seismic energy accumulated in the rock mass. In this paper, modifications of the firing pattern aimed to concentrate the paraseismic vibrations while maintaining the appropriate excavation of the mining face has been verified on the basis of underground tests. The evaluation was based on fragmentation analysis. The obtained results confirmed, that the blasting pattern modifications related to the reducing of the face firing time do not cause significant differences in terms of the appropriate excavation of the mining face.

  • 9.
    Nilsson, Mikael
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Fracturing in the footwall at the Kiirunavaara mine, Sweden2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Kiirunavaara mine is a large scale sub level caving (SLC) mine located near the city of Kiruna in northern Sweden. It is owned and operated by LKAB (Luossavaara-Kiirunavaara AB). The mine produces approximately 28 million tonnes of iron ore annually. Over the last 30 years the mine has experienced a slow but progressive fracturing and movement in the footwall rock mass induced by the SLC operations. The footwall contact which assumes a “slope-like” geometry is partially supported by the caved material from the hangingwall. However, since the late 1980s damage has been observed on the footwall crest as well as within the footwall. Progressive rock mass movement in the footwall is indicated by surface subsidence and visual observations underground. The extent of the damage has traditionally been estimated using empirical relations. Most of the current long term underground infrastructure within the footwall is located at a considerable distance from the ore contact. However, for new developments on deeper levels it is imperative to predict the future extent of the damage volume. Approximating the position of the damage boundary in the footwall at the current state of mining would assist in predicting the extent and characteristics of the damage volume as the mine deepens. LKAB and LTU (Lulea University of Technology) have therefore initiated a joint research project to study the long term stability of the footwall at the Kiirunavaara mine. This paper constitutes part of the work in this research.The paper describes a damage mapping campaign and subsequent analysis of the Kiirunavaara mine footwall to approximate the outer boundary of the damage. The footwall was systematically mapped on 6 levels between 320 and 800 m. The mapping results were then used to interpolate damage lines on the respective levels. The damage lines were used to construct a continuous damage surface between the studied levels. Existing records of damage mapping, monitoring and predictions were reviewed and compared to the results from the current campaign. The new results show that, the outer damage surface appears to remain stationary on the upper levels while new damage was observed on the deeper levels. At levels above 740 m the damage is judged to be mainly controlled by movements along natural discontinuities. At levels below 740 m the majority of the damage seems to be stress induced.

  • 10.
    Nordlund, Erling
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nyberg, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Shirzadegan, Shahin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Westblom, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Zhang, Ping
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Marklund, P-I
    Boliden Mineral AB.
    Sandström, D.
    Boliden Mineral AB.
    Malmgren, Lars
    Samverkan mellan bergförstärkningssystem och bergmassa2011Inngår i: Bergmekanikdag 2011: Föredrag, Stiftelsen bergteknisk forskning - Befo , 2011, s. 19-28Konferansepaper (Annet vitenskapelig)
  • 11.
    Nordlund, Erling
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Zhang, Ping
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Basarir, Hakan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nyberg, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Shirzaegan, S.
    Luleå tekniska universitet.
    Westblom, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Malmgren, Lars
    Marklund, P-I
    Boliden Mineral AB.
    Nordqvist, A.
    LKAB.
    Sandström, D.
    Boliden Mineral AB.
    Rock support system in interaction with the rock2011Konferansepaper (Annet vitenskapelig)
  • 12.
    Nordlund, Erling
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Zhang, Ping
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Dineva, Savka
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mainali, Ganesh
    Impact of fire on the stability of hard rock tunnels in Sweden2015Rapport (Fagfellevurdert)
  • 13.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Behaviour of blast-induced damaged zone around underground excavations in hard rock mass2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The presence of blast-induced damaged zone around an excavation boundary has been an important concern in rock construction. It is generally believed that the presence of this zone can pose problems related to stability and flow and consequently impair the performance and functionality of the excavation. In fact, the immediate consequences of this zone are usually conceived in terms of safety and cost. Hence, some organizations have put in place guidelines for controlling the amount of damage induced by blasting. Since shotcrete or sprayed concrete is a widely used surface rock support, its performance depends primarily on the competence of the damaged zone. However, in some instances the use of shotcrete may unnecessary, but the lack of knowledge of the competency of the damage zone means, it is better not to take chances. It is therefore necessary to increase the knowledge and the understanding of the competency and behaviour of the damaged zone in order to predict the performance and functionality of a rock tunnel. To gain an understanding of the damaged or disturbed zone in general, significant efforts have been made over the last few decades in a broader area; the excavation disturbed zone. These efforts mainly focused on the characterization and classification of the damaged zone. Quantification of this zone has also been done in terms of mechanical, hydraulic and physical parameters, particularly to delineate the extent of the damaged zone. The characterization, classification and quantification of damaged zone were purpose specific and therefore, the definitions for damage zone are different and varying. In this thesis the damaged zone is defined as the zone where the rock has been significantly damaged such that the mechanical properties have been affected and that these changes are measurable by any state of the art measurement techniques. This definition also applies to the blast-induced damage zone. To be able to assess the significance of the blast-induced damage zone and its influence on the performance of an excavation, the mechanical behaviour of this zone must be understood. This thesis is therefore aimed in that direction and thus the objective. Several issues were investigated including; effects and consequences of blast-induced damage zone, most likely failure mechanisms, mechanical parameter sensitivity and their impact on the behaviour of the damaged zone, numerical modelling approach for damaged zone and indicators for failure from a continuum model, etc. A literature review and industrial questionnaire gave the direction for the investigations. Field and numerical methods were employed in the investigations. The results of these investigations are published in a series of papers that make up the thesis. In brief, the main results and conclusions can be summarized as follows: The blast-induced damage zone has been largely defined in terms of its extent and lacks a definition based on its inherent competency parameters, which are directly related to the stability of an excavation. The blast-induced damage zone thickness varies in most practical cases between 0.1 and 1.0 m, with an average ranging from 0.3 m to 0.5 m depending on whether perimeter blasting techniques are used or not. The reduction in the Young's modulus varies anywhere between 10 to 90 % of the undamaged rock value. In a field investigation reported in this thesis the Young's modulus of the damaged rock was found to vary between 50 and 90 % of the value for he undamaged rock mass. The thickness of the damaged zone was between 0.5 and 1.0 m. From the numerical study, the presence of the blast-induced damaged zone did affect the behaviour of the stability quantities, namely; deformation and induced boundary stresses. However, it cannot be concluded if the effects are significant enough to cause problems around an underground excavation in the hard rock mass type studied. The inherent properties of the damaged zone that affected its behaviour, identified in order of their significance are; the deformation modulus, followed by tensile strength and compressive strength. External factors such as the state of the in-situ stresses are seen to significantly influence the behaviour of the damaged zone. With the rock mass type and the in-situ stress regimes used in this thesis, the main failure mechanism within the damaged zone at shallow excavations is tension, while in deep excavations it is compression, as evaluated from the numerical analyses. The influence of the blast-induced damaged zone on failure is evident in shallow excavations but not in deep excavations. This was observed from the coupled continuum-discontinuum models. The study on the shotcrete-rock interface showed that the bond strength of the interface is important for the shear strength. Average bond strength of 0. 5 MPa was determined for interfaces with surfaces roughness with JRC values of 1-3, and 1.4 MPa for those with JRC values of 9-13. These values were determined for low normal load conditions ( MPa) which is often the case when shotcrete is used with rock bolt for rock support. The average adhesion or tensile strength of the interface was determined to be 0.56 MPa.

  • 14.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Blast-induced damage: a summary of SveBeFo investigations2008Rapport (Annet vitenskapelig)
    Abstract [en]

    This report presents a summary of the blast damage investigation carried out by SveBeFo (Swedish Rock Engineering Research) during the period 1991 to 2003 at various hard rock sites in Sweden. The objective of this report is to present a synopsis of the important factors that influence the development and extent of the blast-induced damage zone, nature and characteristics of blast-induced fractures, and a summary of the blast-damage thickness with reference to the existing perimeter blasting damage guidelines for tunnelling and drifting practices in Sweden. Ultimately this report will assist the author in developing numerical models to study the effects of blast-induced damaged zone on stability parameters. It has to be stated clearly that this report is intended as summary and not a reproduction of the works of SveBeFo. It may not also represent the actual conclusions or views of SveBeFo in areas where this author attempted to interpret and conclude from some of the data. Interested readers are strongly urged to consult the SveBeFo publications referenced in this report.The SveBeFo blast damage investigations during the period 1991 to 2003 were carried out at three principle hard rock sites: (i) Vånga granite quarry, (ii) LKAB's Malmberget and Kiruna mines and (iii) SKB's TASQ tunnel. The primary goal of these studies was to improve perimeter blasting guidelines for tunnelling and drifting in hard rock masses in Sweden. Within this scope were several objectives such as: (i) to develop guidelines for blast-induced damage control for drifting and tunnelling in hard rock masses, (ii) devise method for blast damage assessment, (iii) verification of the devised methods in tunnelling and drifting sites. Generally used perimeter blasting techniques, particularly smooth blasting, were employed in the tests. Multiple holes of different, but commonly used, diameters for perimeter holes were used. The explosives used were those commonly used for tunnelling and drifting. After the blasts saw cuts were extracted from the remaining rock, cut into manageable sizes, sprayed with penetrants (to make the blast-induced cracks traceable or visible) and crack parameters (length, quantity and pattern) investigated. The size and pattern of blast-induced damage were observed to depend on various parameters, namely; explosive parameters (explosive type, charge length, initiation method and coupling), blast hole pattern (burden, spacing and hole diameter), in-situ rock mass parameters (geology, in-situ stress, and rock strength and stiffness) and water in the holes. The thickness of the observed damage ranged between 0.1 and 1.2 m. An average damage thickness of 0.5 m was observed in the Kiruna and Malmberget mine drifts and 0.3 m in SKB's ÄSPE/TASQ tunnel and Vånga granite quarry.

  • 15.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Blast-induced damaged zone studies: Final Report to Trafikverket2011Rapport (Annet vitenskapelig)
    Abstract [en]

    This report is a summary and conclusions from the study on Blast-Induced Damage around underground excavations in hard rock, which was carried out as a PhD research project by the author. The project was funded by Vägverket and the research was conducted at the Division of Mining and Geotechnical Engineering at Luleå University of Technology. The work resulted in several publications; a PhD thesis, journal articles, conference articles and technical reports. The publications can be downloaded from: http://www.ltu.se/staff/d/davsai?l=en. This final report is compilation of the important elements from these various publications.Because the Blast-Induced Damaged Zone (BIDZ) is generally perceived to have a negative impact on the economics and performance of a tunnel many studies have been conducted to delineate the extent of the BIDZ. The primary goal has been to device ways to control or minimise the extent of this zone. As a result guidelines have been developed by concerned authorities, such as for example AnläggningAMA-98 (1999), to control the extent of BIDZ during tunnel construction. These guidelines however do not give recommendations about the strength and stiffness properties of the BIDZ, which are the most important parameters that control its behaviour and ultimately influence the stability and performance of tunnel.The extent of the BIDZ in majority of the practical cases varied between 0.1 and 1.0 m, with an average ranging from 0.3 m to 0.5 m. The stiffness magnitudes of this zone were as low as 10% to as high as 90% of that of the undamaged rock mass. Field investigation at Kiirunavaara underground mine (Malmgren et al, 2007) showed the stiffness of the BIDZ to vary between 50 and 90% of that of the undamaged rock mass, while the thickness ranged from 0.5 to 1.0 m. Although it was possible to deduce the modulus of the BIDZ the strength however, is the most difficult to measure or estimate. The most generic way to estimate the strength of the BIDZ is the use of a rock mass classification system in conjunction with a strength criteria, which was the approach used in the research by this author.Numerical studies of the BIDZ by this author showed that, the presence of this zone does affect the overall response of the near-field rock mass. This therefore implies the need for consideration of this zone during the tunnel design stage. The strength and stiffness of this zone were also found to affect the type of failure around the tunnel and its extent. However, it not is possible to state by what degree the BIDZ will affect the performance of a tunnel as it is relative. It is therefore wise to use guidelines to minimise damage even though it may be costly and unnecessary. In any case it would be beneficial to consider the sensitivity of an excavation, both subjectively and objectively, before emphasising the seriousness to stick to the blast damage guidelines.

  • 16.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Damaged rock zone around excavation boundaries and its interaction with shotcrete2004Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    When an excavation is carried out in a body of rock, the mechanical, hydraulic and physical properties of the rock surrounding the excavation will be disturbed. The zone in which these occur is called the Excavation Disturbed Zone (EDZ) and must be represented in the quantitative assessment of the near-field host rock. Therefore, numerous investigations of the EDZ have been conducted worldwide and are reported in for example, the International EDZ Workshops of 1996 and 2003. By definition EDZ encompasses both, the zone where the rock is physical damaged (mechanical properties are permanently affected) and the zone where the rock is only disturbed (mechanical properties not significantly affected). The former, i.e. the damaged zone, will impact significantly the overall performance of an excavation since the mechanical properties of this zone are considerably reduced. This zone is referred to as the Damaged Rock Zone (DRZ) and is the focus of this study. The strength and stiffness of this zone are important governing parameters that determine how this zone behaves, as well as how it zone interacts with shotcrete as surface rock support. Despite the fact that much has been covered on the subject of excavation damaged zone, most of these work were mainly focused on, (1) identifying factors that influence the development and extent of the damage zone, and (2) quantitatively measure the extent of the damaged zone. The main goal of these studies was for the reduction of this zone. Since, it has never been possible to completely eliminate this zone what is left is in fact to quantify this zone it terms of its strength and stiffness, in order to visualize how the excavation will perform with the presence of DRZ, including its interaction with the rock support systems, which will ultimately lead to recommendations for support optimization. In this regard only few researchers have gone a step further, from just delineating the damaged zone, to quantitatively estimate the stiffness of this zone. Although it is also desirable to measure the strength of the DRZ, it is at this point in time practically difficult and not to mention the complex physics involved. This thesis, as well as the future research, will focus on the behavior of the DRZ and its interaction with surface rock support. Questions about how the strength and stiffness vary with respect to their position and magnitude around the excavation will also be investigated with the help of numerical methods. In the study reported herein however, the primary focus is on, 1) the literature review aspect and 2) stage one field and experimental work on the DRZ and its interaction with shotcrete.

  • 17.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Damaged rock zone study: a progress report2008Rapport (Annet vitenskapelig)
    Abstract [en]

    The subject of the damaged rock zone around an underground excavation is very complex. Much of these complexities relate to the physics of the rock properties and the highly anisotropic conditions of the EDZ. In rock physics, for example, the sough after rock properties such as Young's modulus (E) and the strength parameters (óc, c, ö, etc) are tensor quantities - that is they have spatial characteristics (3-dimensional). So the question usually is: Is it sufficient to relate these parameters (which are tensors) to vector quantities such as velocity (which is one- dimensional)? Obviously, there is no mathematical relationship for this. The anisotropy within the EDZ also complicates any process that attempts to estimate the magnitude of these properties. A drill and blast excavation will result in complex fracture patterns (irregularly shaped, cracks ranging from micro to macro sizes, rock bridges, etc). All these complexities will affect the kinematics of rock deformation and strength characteristics. A large volume of publications is available on investigations into the excavation disturbed zone. However, much of these investigations have focussed on identifying the factors affecting the development and extent of this zone, with the primary goal of minimising or if possible to completely eliminate this zone, which though is not possible. A questionnaire on EDZ was send to various organisations and individuals. The responses revealed various views on the EDZ. The mining industry for example, sees the EDZ from two sides of the coin: (i) it can act as protective blanket (destressed zone) by pushing high stresses further into the rock and in doing so protect the excavation, (ii) it can also jeopardise the safety of personnel and equipment as well as resulting in increased support costs. For nuclear waste isolation group the EDZ will provide a flow path for nuclear radiation to reach the atmosphere. Further still, for the civil engineering, the problem is largely related to stability, and maintenance and operational costs. Each of these cases is unique since the requirements are different. Which parameters are important and which factors need attention will depend on the nature and purpose of the excavation.

  • 18.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Determination of specific rock mass failure envelope via PFC and its subsequent application using FLAC2008Inngår i: Continuum and distinct element numerical modeling in geo-engineering 2008: Proceedings of the 1st International FLAC/DEM Symposium, Itasca , 2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    While pursuing a numerical study on the behavior of the rockmass near a tunnel boundary at shallow depths, by continuum methods, it was realized that the yield mechanisms were not accurately captured using the input parameters obtained directly through the Hoek-Brown-GSI empirical system. It was evident that unless these mechanisms were accurately captured the behavior of the near-field rockmass cannot be correctly simulated. A question was then raised if PFC could be used to obtain a simple failure envelope/model for the rockmass in question and then use this model in the FLAC simulations - thus the object of this paper. The paper is presented in two parts as; (i) "numerical laboratory tests" involving biaxial compression and Brazilian tests on "synthetic rockmass samples" to determine the failure model and (ii) the subsequent application of the model in FLAC. The results are then presented and discussed, with the main conclusion that PFC can be used to determine the values of the input parameters for a continuum model.

  • 19.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Project: Mechanical behaviour of the damaged rock zone around excavation boundaries2007Annet (Annet (populærvitenskap, debatt, mm))
  • 20.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Simulation of truck haulage queue system at an open mine using SIMIAN2008Inngår 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. 607-616Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Simulation methods can be used in a variety of queuing situations: boats waiting for an unloading or loading quay, banking tellers, supermarket tills, logs passing through a sawmill, passengers arriving at an international airport and so forth. In mining operations it can be used for example, to simulate flow of ore through a processing plant or the flow of haul trucks in an open pit. The purpose could be for ore blending, equipment optimisation and production target realization. This paper presents the simulation of a truck haulage queue system at a large open pit mine using SIMIAN simulation language. The statistical data used in the model are derived from real time data obtained from a large open pit mine in Papua New Guinea. This mine is also used as a case for the models developed herein. The movement of trucks through the open pit is simulated using the configuration prevalent during the time of data collection.

  • 21.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Stability analysis of the blast-induced damage zone by continuum and coupled continuum-discontinuum methods2010Inngår i: Engineering Geology, ISSN 0013-7952, E-ISSN 1872-6917, Vol. 116, nr 1-2, s. 1-11Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The presence of a blast-induced damage zone (BIDZ) around a tunnel boundary is of significant concern mainly with regard to safety, stability, costs and the overall performance of the tunnel. The BIDZ is essentially characterized by reduction in strength and stiffness, and increase in permeability. Guidelines have been developed based on perimeter blasting experiences and overbreak characterization to regulate damage due to blasting. Although the over-break approach of assessing the degree of blast-induced damage is practical, the method does not provide a measure of the competency of the damaged rock. Very often it is important to know how the damaged rock mass will behave under any given conditions. In this paper a series of numerical analyses was performed using continuum and coupled continuum-discontinuum methods to study the behaviour of the blast-induced damage zone. In the coupled continuum-discontinuum method FLAC and PFC2D were coupled together. The inner segment of the model was simulated using PFC2D, while the outer segment was simulated using FLAC. This enabled the tracking of failure and fallout from the PFC2D model. The tunnel was excavated within the PFC2D segment. Blast-induced radial cracks were traced and individually implemented in the models. Models were also run independently in FLAC and Phase2 and the results were compared to those of the coupled models. The results show that the failure around the tunnel was confined in most parts to the damaged zone at shallow depths, but not in deep excavations. The failures and fallouts mapped with the coupled models were consistent with practical observations. Since the continuum models cannot simulate failure, results from the coupled model were used to identify indicators for failure in the continuum models. It was seen that yielding due to volumetric straining (in FLAC) and 100% yielded elements (in Phase2) were consistent with the failures mapped in the coupled models for shallow excavations, but was less consistent for deep excavations

  • 22.
    Saiang, David
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Basarir, Hakan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Assessment of slope stability using fuzzy sets and systems2013Inngår i: International Journal of Mining, Reclamation and Environment, ISSN 1748-0930, E-ISSN 1748-0949, Vol. 27, nr 5, s. 312-328Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To assess the stability of slopes, mining and geotechnical engineers frequently use empirical rock mass classification and characterisation systems. These methods are practical and often very useful in the preliminary design stage. Slope mass rating (SMR) system is one of the commonly used empirical methods to assess the stability of slopes. The SMR is obtained correcting basic rock mass rating (RMR) using four joint adjustment factors that consider the geomechanical relationship between the slope face and the joint affecting rock mass as well as the excavation method used. The factors included in the SMR system such as basic RMR, and correction factors involve some drawbacks such as uncertainties sourced from qualitative criteria, sharp class boundaries and fixed rating scales. These drawbacks are sourced from the complex nature of rock mass. To deal with these uncertainties, the fuzzy set theory is applied in this study to reliably determine basic RMR and adjustment factors. It was seen that fuzzy set theory can sufficiently cope with the common drawbacks in the determination of factors included in the SMR system.

  • 23. Saiang, David
    et al.
    Gywnn, Xander
    SRK Consulting Sweden AB.
    Marshall, Neil
    SRK UK Ltd.
    Hoek-Brown vs. Mohr-Coulomb: Results from a three-dimensional open-pit/underground interaction model2014Konferansepaper (Fagfellevurdert)
  • 24.
    Saiang, David
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Malmgren, Lars
    The shotcrete/rock interface: direct shear, tension and compression2004Inngår i: Bergmekanikdag 2004, 2004, s. 99-109Konferansepaper (Annet vitenskapelig)
  • 25. Saiang, David
    et al.
    Malmgren, Lars
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Laboratory tests on shotcrete-rock joints in direct shear, tension and compression2005Inngår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 38, nr 4, s. 275-297Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of laboratory tests was performed on cemented shotcrete-rock joints to investigate the strength and stiffness of the interfaces, while simulating field conditions as close as possible. The direct shear test formed the core of the experimental work, while the tension and compression tests were complementary. To simulate loading conditions experienced in practical cases the direct shear tests were performed under fairly low normal stresses. In most practical cases when shotcrete is used with rock bolts, the normal load on shotcrete lining seldom exceeds 0.2 to 0.5 MPa. The direct shear test results show that, for such normal load range the shear strength is determined by the bond strength for genuinely bonded shotcrete-rock interfaces. For higher normal stresses (σn > 1.0 MPa), which rarely exist at the shotcrete-rock interface, the shear strength is largely influenced by friction resulting in the cohesive strength being less significant. Assessment of the shear surface revealed that the steel fibres in the shotcrete appeared to contribute significantly to the frictional component. The shear and normal stiffnesses of the interface were also determined, which were in principal the stiffnesses of the bond. An interesting observation was the complex interaction at the interface and the mechanisms that controlled the peak shear strength which depended on the surface roughness, the existence of natural flaws and the normal load.

  • 26.
    Saiang, David
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Malmgren, Lars
    Nordlund, Erling
    Strength and stiffness of shotcrete-rock interface: a laboratory study2004Inngår i: Ground Support in Mining and Underground Construction: Proceedings of the fifth international symposium on ground support / [ed] Ernesto Villaescusa; Yves Potvin, Leiden: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 2004, s. 555-564Konferansepaper (Fagfellevurdert)
  • 27. Saiang, David
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    A parameter study of the damaged rock zone around shallow tunnels in brittle rock2006Inngår i: Rock Mechanics in Underground Construction: Proceedings of the ISRM International Symposium 2006 and the 4th Asian Rock Mechanics Symposium / [ed] C.F. Leung; Y.X. Zhou, Singapore: World Scientific and Engineering Academy and Society, 2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    As part of an ongoing study on the mechanical characteristics of the damaged rock zone (DRZ) around underground excavations and its influence on the overall performance of the excavation, a parameter study was carried out using the continuum method of numerical analysis. This assisted in identifying the sensitivity of the parameters tested, thereby laying the groundwork for further numerical investigation. The main parameters investigated include the extent of DRZ, the strength and stiffness of DRZ, and the depth of the excavation. The main quantity used to test the sensitivity of these parameters is the response of induced stresses around the excavation boundary resulting from the variation in these parameters. In the study presented in this paper, typical in-situ stress and rock mass conditions observed for shallow tunnelling projects in Sweden are used. The results clearly demonstrate the effect of DRZ on the excavation as well as the criticality of various parameter combinations. The strength of DRZ although sensitive, is the most complex to define and the tool used in this study to determine the empirical plastic strength components, namely cohesion and friction, is felt to be uncertain.

  • 28.
    Saiang, David
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Blast-induced damaged around tunnels: effects, concerns and numerical assessment2008Inngår i: Bergmekanikdag: föredrag vid Bergmekanikdag i Stockholm 10 mars 2008, 2008, s. 41-50Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Blast-induced damage is an important concern to construction of underground excavations. These concerns relate mainly to the after-blast effects on stability, water inflow, safety and costs. Such concerns have led to introduction of guidelines to regulate the extent of tolerable damage due to blasting. However, a true definition for blast-induced damage still remains vague, since the parameters used in measuring damage seldom relate to the stability parameters of the damaged rock. To assist in the better understanding of the effects of blast-induced damage a survey was conducted by the authors in late 2005 to obtain the views of practitioners (clients and contractors) involved in underground rock excavations. This paper presents firstly, a condensed summary of the responses from the survey. Secondly, results from the numerical assessment of the effects of the blast-induced damaged rock with respect to deformation and stability parameters are presented. Inputs based on typical Swedish rock mass conditions were used in the modelling, while the modelling assumptions were based on blast-induced damage observations from SveBeFo field study reports.

  • 29. Saiang, David
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Destressing and Preconditioning of Rock2005Rapport (Annet vitenskapelig)
  • 30. Saiang, David
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Failure mechanisms around shallow tunnels in brittle rock2007Inngår i: 11th Congress of the International Society for Rock Mechanics: The Second Half Century of Rock Mechanics / [ed] L.R. e Sousa; C. Olalla; N.F. Grossman, Taylor and Francis Group , 2007, Vol. 2, s. 883-890Konferansepaper (Fagfellevurdert)
    Abstract [en]

    As part of an ongoing study on the mechanical characteristics of the damaged rock zone (DRZ) around a tunnel boundary and its influence on the overall behaviour of the near-field host rock, a numerical study was conducted to investigate the dominant rock mass failure mechanisms around shallow tunnels located in a body of brittle rock mass. Preliminary studies have clearly indicated that, the rock mass behaviour was largely dictated by the different yield mechanisms involved. These mechanisms appear to be multifarious due to the complex state of the induced stresses around the tunnel boundary at shallow depth. Some of these yield mechanisms are often difficult to capture using the traditional yield criterion such as the Mohr-Coulomb. In the study reported in this paper a series of computer simulations were performed using typical in-situ stresses and rock mass conditions generally encountered in shallow tunnelling projects in Sweden. The presence of a disturbed/damaged rock zone with finite thickness was also added into the models. Due to the nature of the simulations the FLAC2D code was selected and used. The values for the input parameters were estimated using a systematic procedure. To prevent premature tensile yielding due to transient loading traction was applied during tunnel excavation. The results show that, the dominant yield mechanism occurring around the shallow tunnel in brittle rock is the one of tensile nature. Compressive mechanisms do occur but seems to be less critical to overall performance of the tunnel. However, they do influence the overall behaviour of the rock mass response. The results further indicated that, the ‘true' locality of instability could be predicted from elastic analyses, by observing if all the major principle stresses are in tension in that locality. The shear strain increment plots of the model in plastic mode further supported this observation.

  • 31.
    Saiang, David
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Ground support modelling involving large ground deformation: Simulation of conceptual cases – Part 22016Inngår i: Proceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    As a continuation of Part 1 of ground support modelling involving large ground deformation by Saiang and Nordlund (2016) this paper presents the conceptual models and results from the typically observed cases throughout the Kristineberg mine. The Part 1 of the paper focused primarily on results from measurements carried out at the J-orebody, whereas the Kristineberg mine consists of many ore bodies or lenses within the VMS (volcanic massive sulphides). Part 2 therefore presents some of the typically observed rock mass behaviours throughout the mine. The mine geology is very complex for each of the orebody due to the multiple phases of wall rock alterations and various geological processes that occurred throughout the history of the deposit. This history also included both local and regional events of folding, faulting and shearing. Despite the notable differences in the local geology around the different orebodies, there is nevertheless, a general trend that the stability of the stopes throughout the mine are in principal controlled by the altered wall rocks, the presence of other lithologies capable of inhibiting deformation and the geometry of the stopes themselves as demonstrated in Part 1.

  • 32.
    Saiang, David
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Ground support modelling involving large ground deformation: Simulation of field observations – Part 12016Inngår 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), 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Kristineberg mine has a long history of large ground deformation which consequently incites ground control problems for the mine. Over the years the mine has developed various mining techniques, backfilling and ground support procedures to manage this problem. In general the ground control problems at the mine are highly influenced by the wall rock geology. The wall rock, that is the footwall and hanging wall, comprise of highly altered chlorite schist, which are internally referred to as talc-schist. They very often occur as seams with thickness barely ranging from 0.1 m to as wide as 3.0 m. Coupled with high ground stresses the talc squeezes and slides into the stope if undercut by the excavation, or either bends or bulges inwards when exposed but not undercut depending on the loading direction. The deformation magnitudes have often been reported to be in the order of 0.2 to 0.5 m and seldom up to 1.0 m. Conventional rock support system, consisting of fibre re-enforced shotcrete and rebar rock bolts, has regularly failed under these conditions. As part of Ground Support Research Initiative at Luleå University of Technology a monitoring program was designed to measure ground deformation and the response of the ground support system. Numerical modelling was conducted to capture the responses as observed during monitoring. The numerical models revealed all the typical mechanisms of instability that have been conceptualized through observations and earlier studies. Talc obviously was the most influential lithology that controlled the deformation characteristics of the stope and ultimately on the rock support system. Combinations of bending, bulging, shearing and tensile mechanisms induced a complex loading pattern on the rock support system. Often the rock bolts, for example, would experience all of these mechanisms at once or during different stages of the excavation rounds as a cut is developed.

  • 33.
    Saiang, David
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Numerical Analyses of Field Monitoring in Stope J10-3 at Kristineberg Mine2017Rapport (Fagfellevurdert)
  • 34. Saiang, David
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Numerical analyses of the influence of blast-induced damaged rock around shallow tunnels in brittle rock2009Inngår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 42, nr 3, s. 421-448Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Most of the railway tunnels in Sweden are shallow-seated (<20 m of rock cover) and are located in hard brittle rock masses. The majority of these tunnels are excavated by drilling and blasting, which, consequently, result in the development of a blast-induced damaged zone around the tunnel boundary. Theoretically, the presence of this zone, with its reduced strength and stiffness, will affect the overall performance of the tunnel, as well as its construction and maintenance. The Swedish Railroad Administration, therefore, uses a set of guidelines based on peak particle velocity models and perimeter blasting to regulate the extent of damage due to blasting. However, the real effects of the damage caused by blasting around a shallow tunnel and their criticality to the overall performance of the tunnel are yet to be quantified and, therefore, remain the subject of research and investigation. This paper presents a numerical parametric study of blast-induced damage in rock. By varying the strength and stiffness of the blast-induced damaged zone and other relevant parameters, the near-field rock mass response was evaluated in terms of the effects on induced boundary stresses and ground deformation. The continuum method of numerical analysis was used. The input parameters, particularly those relating to strength and stiffness, were estimated using a systematic approach related to the fact that, at shallow depths, the stress and geologic conditions may be highly anisotropic. Due to the lack of data on the post-failure characteristics of the rock mass, the traditional Mohr-Coulomb yield criterion was assumed and used. The results clearly indicate that, as expected, the presence of the blast-induced damage zone does affect the behaviour of the boundary stresses and ground deformation. Potential failure types occurring around the tunnel boundary and their mechanisms have also been identified

  • 35.
    Saiang, David
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Numerical Analysis of Large Ground Deformation and Rock Support Interaction at Kristineberg Mine, Sweden2014Rapport (Fagfellevurdert)
    Abstract [en]

    Numerical analyses have been performed to study the interaction between rock support and rock mass in response to large ground deformation at the Kristineberg mine. Ground control problems at the Kristineberg mine is known to be highly influenced by the wall rock geology. The wall rock, that is the footwall and hanging wall, comprise of highly altered chlorite schist, which is internally referred to as talc-schist, very often occur as seams with thickness barely ranging from 0.1 m to as high as 3.0m. These material squeeze and slide into the stope if undercut by the excavation or bends inwards if exposed but not undercut. The magnitude of the deformation has often been reported to be in the order of 0.2 to 0.5 m and seldom up to 1.0 m. Conventional rock have support consisting of fibre re-enforced shotcrete and rebar regularly failed under these conditions. A field investigation has therefore been carried out to study the response of the current rock support system to the different mechanisms of instability at the Kristineberg mine. In addition, a new rock bolt type, called the D-bolt, has been tested during the field tests. The numerical study revealed all the typical mechanisms of instability that have been conceptualized through observations. The performance of rebar is clearly affected by the combinations of bending, shearing and tensile mechanisms. D-bolt, on the other hand, is a ductile rock bolt and, its performance appears to sustain large deformations before showing signs of yielding. However, more work needs to be done before proper conclusions can be made about the performance of the D-bolt under such conditions.

  • 36. Saiang, David
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Numerical study of the mechanical behaviour of the damaged rock mass around an underground excavation2008Inngår 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. 803-813Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The behaviour of the rockmass immediately surrounding an excavation (e.g. open pit slope, underground mine drift, etc.) will ultimately determine the overall performance of the excavation itself and the general operational safety, as well as providing the basis for support requirement decisions. Very often the near-field rockmass is significantly disturbed or damaged by blasting and redistribution of stresses. Any damage or disturbance to the near-field host rock will result in reduction to the strength and stiffness of the rockmass and consequently affect the stability of the excavation. In this paper a series of numerical analyses was conducted to study the behaviour of the near-field host rock, with a damaged rock zone around the excavation boundary. Typical underground mining drift geometry was used in building the models. The in-situ rockmass parameters are those typically encountered in the Swedish hard rockmass system, including the in-situ stresses. The results show that, the stability parameters; induced stresses and ground deformation, were observably affected by the presence of the damaged rock zone, as expected.

  • 37. Saiang, David
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Pérez, Kelvis
    Damaged rock zone around underground excavation boundaries2005Rapport (Annet vitenskapelig)
  • 38.
    Sjöberg, Jonny
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Perman, F
    Vattenfall.
    Leander, M
    Vattenfall.
    Saiang, David
    Three-dimensional analysis of tunnel intersections for a train tunnel under Stockholm2006Inngår i: North American Tunneling: proceedings of the North American Tunneling 2006 Conference, 10-15 June 2006, Chicago, USA / [ed] Levent Ozdemir, London: Taylor and Francis Group , 2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Citybanan commuter train tunnel will comprise a 6 km long, double-track train tunnel to be constructed in rock under Stockholm City. In this paper, analysis of the intersections between the planned train tunnel and so-called "energy tunnels" is described. The objective of this analysis was twofold: (i) to predict deformations and stability of the energy tunnels caused by excavation of the train tunnel, and (ii) to determine required rock reinforcement for the train tunnel. Analysis was conducted primarily using the three-dimensional finite difference program FLAC3[). The analysis results showed that only minor deformations can be expected in the energy tunnels due to the excavation of the train tunnel, and that the overall stability of the tunnels was satisfactory. Furthermore, the results could be used to confirm a proposed rock reinforcement scheme for the train tunnels, thus securing the stability of the load-bearing structure for the rock tunnel.

  • 39.
    Svartsjaern, Mikael
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Discrete Element Modelling of Footwall Rock Mass Damage Induced by Sub-Level Caving at the Kiirunavaara Mine2017Inngår i: Minerals, ISSN 2075-163X, E-ISSN 2075-163X, Vol. 7, nr 7, artikkel-id 109Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Kiirunavaara mine is one of the largest sub-level-caving (SLC) mines in the worldand has been in underground operation for more than 50 years. The mine has been the focus ofseveral case studies over the years. The previous works have either focused on the caving of thehanging wall, using the footwall as a passive support, or focused on the footwall using the hangingwall to apply a passive load. In this updated study the findings of the previous case studies arecombined to study the interaction between the caving hanging wall, the developing cave rock zoneand the footwall. The geological data for the rock types in the mine area are used to derive upperand lower limits for the geomechanical parameters calibrated for numerical models in the previousstudies. The calibrated parameters are used as inputs to a numerical model constructed usingItasca’s Particle-flow-code (PFC) encompassing a mine-scale 2D section at the mid portion of themine. The model captures the failure locations well in the footwall underground and indicatesdamage development without a coherent large-scale failure. The trend in subsidence data on thehanging wall is adequately simulated but the magnitude of deformation is underestimated. Theinput strength for the hanging wall was lowered to study the impact of hanging wall strength onfootwall damage development. It is shown that when the footwall strength is kept constant, whilelowering the hanging wall strength, the extent of damage and magnitude of displacements in thefootwall increases. From these observations it is argued that the hanging wall and footwall cannotbe studied independently for the Kiirunavaara mine since the cave rock zone significantly affectsthe damage development in both walls.

  • 40.
    Svartsjaern, Mikael
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mäkitaavola, Karola
    Loussavaara-Kiirunavaara Limited, Lulea.
    Underground Footwall Monitoring at the Sublevel Caving Mine – Kiirunavaara, Sweden2016Inngår i: Seventh International Conference & Exhibition on Mass Mining: (MassMin 2016), Sydney: The Australian Institute of Mining and Metallurgy , 2016, s. 773-780Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Kiirunavaara mine is a large-scale (28 Mt per annum) iron ore mine located in northern Sweden. The mine is owned and operated by Luossavaara-Kiirunavaara Aktiebolag (LKAB) using sublevel caving (SLC). The SLC area underlies an open pit decommissioned in the 1950s, the current main SLC haulage level is situated at an depth of 1100 m. The main orebody dips 60 degrees to the east with a distinct boundary defining the hanging wall to the east and footwall to the west. Since the 1980s damage has been observed both in the footwall rock mass as well as on the footwall crest of the open pit. Recent investigations indicate that the underground footwall damage is primarily controlled by large-scale slope failure mechanisms. Structurally controlled near-vertical planar shear failures in the upper footwall appear to be driven or facilitated by a step-path like curved shear failure situated in a zone starting ca 250 m, and intersecting the SLC about 100 m above the active mining level. To confirm this failure evolution a pilot underground measuring system has been designed and installed to monitor the expected rock mass displacements indicated by numerical models based on the above mechanisms. The systems consists of 50 m time domain reflectometry (TDR) coaxial cables installed in the footwall both across and away from an estimated damage extent boundary to monitor shear movements along natural joint surfaces. The TDR installation is combined with long extensometers to facilitate differentiation between diffuse shear and rock mass normal expansion. Additionally, a low-tech system of tape extensometer lines are installed in drifts and stopes running perpendicular to the ore strike to monitor horizontal displacements in the infrastructure as the footwall ‘slope’ loses confinement during mining advance when the mined out areas are replaced by caved rock from the hanging wall.

  • 41.
    Svartsjaern, Mikael
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Eitzenberger, Andreas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Conceptual Numerical Modeling of Large-Scale Footwall Behavior at the Kiirunavaara Mine, and Implications for Deformation Monitoring2016Inngår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 49, nr 3, s. 943-960Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Over the last 30 years the Kiirunavaara mine has experienced a slow but progressive fracturing and movement in the footwall rock mass which is directly related to the sublevel caving (SLC) method utilized by Luossavaara-Kiirunavaara Aktiebolag (LKAB). As part of an on-going work, this paper focuses on describing and explaining a likely evolution path of large-scale fracturing in the Kiirunavaara footwall. The trace of this fracturing was based on a series of damage mapping campaigns carried out over the last two years, accompanied by numerical modelling. Data collected from the damage mapping between mine levels 320 and 907 m was used to create a 3D surface representing a conceptual boundary for the extent of the damaged volume. The extent boundary surface was used as the basis for calibrating conceptual numerical models created in UDEC. The mapping data, in combination with the numerical models, indicated a plausible evolution path of the footwall fracturing that was subsequently described. Between levels 320 and 740 m the extent of fracturing into the footwall appears to be controlled by natural pre-existing discontinuities, while below 740 m there are indications of a curved shear or step-path failure. The step-path is hypothesised to be activated by rock mass heave into the SLC zone above the current extraction level. Above the 320 m level the fracturing seems to intersect a sub-vertical structure that daylights in the old open pit slope. Identification of these probable damage mechanisms was an important step in order to determine the requirements for a monitoring system for tracking footwall damage. This paper describes the background work for design of the system currently being installed.

  • 42.
    van Eldert, Jeroen
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Schunnesson, Håkan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Johansson, Daniel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Application of Measurement While Drilling Technology to Predict Rock Mass Quality and Rock Support for Tunnelling2019Inngår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453XArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A tunnelling project is normally initiated with a site investigation to determine the in situ rock mass conditions and to generate the basis for the tunnel design and rock support. However, since site investigations often are based on limited information (surface mapping, geophysical profiles, few bore holes, etc.), the estimation of the rock mass conditions may contain inaccuracies, resulting in underestimating the required rock support. The study hypothesised that these inaccuracies could be reduced using Measurement While Drilling (MWD) technology to assist in the decision-making process. A case study of two tunnels in the Stockholm bypass found the rock mass quality was severely overestimated by the site investigation; more than 45% of the investigated sections had a lower rock mass quality than expected. MWD data were recorded in 25 m grout holes and 6 m blast holes. The MWD data were normalised so that the long grout holes with larger hole diameters and the shorter blast holes with smaller hole diameters gave similar results. With normalised MWD data, it was possible to mimic the tunnel contour mapping; results showed good correlation with mapped Q-value and installed rock support. MWD technology can improve the accuracy of forecasting the rock mass ahead of the face. It can bridge the information gap between the early, somewhat uncertain geotechnical site investigation and the geological mapping done after excavation to optimise rock support.

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