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  • 1.
    Bjarnason, B.
    et al.
    Luleå University of Technology.
    Ljunggren, Christer
    Luleå University of Technology.
    Stephansson, Ove
    Luleå University of Technology.
    New developments in hydrofracturing stress measurements at Luleå University of Technology1989In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 26, no 6, p. 579-586Article in journal (Refereed)
    Abstract [en]

    Instrument and theoretical developments in hydrofracturing stress measurements at Lulea University of Technology since the first workshop in Monterey in 1981 are described and the general experience with the method in Sweden is summarized. A new field unit is described which includes a 1000-m long multihose and a 100 MPa water pump. Stress measurements by means of injection tests on preexisting fractures have been introduced and applied at two sites in Sweden. A theory has been developed which permits estimation of the maximum and minimum horizontal stresses in cases where transverse hydrofractures are created in the borehole wall instead of axial.

  • 2.
    Bro, A.
    Luleå University of Technology.
    Three-dimensional styrofoam models of blocky rock masses1991In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 28, no 1, p. 109-113Article in journal (Refereed)
  • 3.
    Carlsson, J.
    et al.
    Luleå University of Technology.
    Sundin, Karl-Gustaf
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Lundberg, Bengt
    Luleå University of Technology.
    Method for determination of in-hole dynamic force-penetration data from two-point strain measurement on a percussive drill rod1990In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 27, no 6, p. 553-558Article in journal (Refereed)
    Abstract [en]

    The aim of the present investigation is to establish a testing method suited for determination of in-hole dynamic force-penetration data for non-uniform standard percussive drill rod-bit configurations. The method is based on a version of the method of two-point strain measurement, which permits non-uniform rods, i.e. rods with variable characteristic impedance. This version allows normal force and particle velocity to be evaluated at an arbitrary cross-section of a homogenous non-uniform elastic rod from strain measurements performed at two different cross-sections of the same rod. The main problem of this investigation is to assess whether the influence of threads can be considered insignificant. As a part of the study force-penetration relationships have been determined for the penetration of a standard Sandvik Rock Tools button bit into Swedish Bohus granite.

  • 4.
    Claesson, Johan
    et al.
    Department of Building Physics, Lund University.
    Follin, S.
    Department of Engineering Geology, Lund University.
    Hellström, Göran
    Wallin, N-O
    Department of Mathematics, Lund University.
    On the use of the diffusion equation in test case 6 of DECOVALEX1995In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 32, no 5, p. 525-528Article in journal (Refereed)
  • 5.
    Forsman, Bo
    et al.
    Luleå University of Technology.
    Pan, Chan Lang
    Central South University of Technology, Changsha.
    Shear properties of fragmented rock masses: model tests and theories1989In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 26, no 1, p. 25-36Article in journal (Refereed)
    Abstract [en]

    In material handling, such as loading and gravity flow, shear strength is one of the most important physical properties. This work deals with important factors influencing the shear strength of fragmented rock in order to give a better theoretical background for developing rock loading techniques.Shear tests were performed on three types of fragmented rock mass samples to investigate the parameters particle size and distribution, moisture content and compaction of the material.From the standpoint of deformation energy, a shear strength envelope equation has been deducted for loose rock material. A comparison has been made between the results calculated with this equation and Coulomb's equation.The results obtained for each investigated parameter include the relation between shear force and shear displacement during constant normal force, the volume change, the deformation energy change and the internal friction angle.

  • 6.
    Hakami, H.
    et al.
    Luleå University of Technology.
    Alm, Ove
    Luleå University of Technology.
    Stephansson, Ove
    Luleå University of Technology.
    Gauged sleeve for controlled testing of rock1987In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 24, no 6, p. 375-378Article in journal (Refereed)
    Abstract [en]

    Electrical resistance strain gages, each 5 cm in length, were embedded at a depth of 1 mm, inside a Cil Monothane sleeve of thickness 2 mm. Cil Monothane A80 is a single component and non-toxic, heat-cure-pour polyurethane elastomer. It has sound elasto-plastic properties when cured. It was supplied by Compounding Ingredients Ltd, England. The strain gages cover about 95% of the circumference of the sleeve. The position of the strain gages corresponds to the mid-height of the rock sample

  • 7.
    Jing, L.
    et al.
    Royal Institute of Technology.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Stephansson, Ove
    Royal Institute of Technology.
    A 3-D constitutive model for rock joints with anisotropic friction and stress dependency in shear stiffness1994In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 31, no 2, p. 173-178Article in journal (Refereed)
  • 8.
    Jing, Lanru
    et al.
    Luleå University of Technology.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Stephansson, Ove
    Luleå University of Technology.
    An experimental study on the anisotropy and stress-dependency of the strength and deformability of rock joints1992In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 29, no 6, p. 535-542Article in journal (Refereed)
    Abstract [en]

    The anisotropy and stress-dependency of the strength and deformability of rock joints were investigated experimentally through shear tests of concrete replicas of natural rock joints. 50 concrete replicas of two natural granite joints were sheared on a servo-controlled hydraulic test frame under different magnitudes of normal stress and in different shear directions. Significant anisotropy in both the friction angle and shear stiffness of concrete replicas of joints were observed and both of them change with the variation of normal stress. The rates of dilatancy and contraction of joint samples appear to be different during cyclic shear tests, depending very much on the initial conditions of sample surfaces. Empirical relations were then postulated to describe these newly found properties of joint samples and used in developing new constitutive models for rock joints

  • 9.
    Karlsson, Lars G.
    et al.
    Luleå University of Technology.
    Lundberg, Bengt
    Luleå University of Technology.
    Sundin, Karl-Gustaf
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Experimental study of a percussive process for rock fragmentation1989In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 26, no 1, p. 45-50Article in journal (Refereed)
    Abstract [en]

    The efficiency of a percussive process for fragmentation of rock and similar materials has been studied experimentally. The percussive system comprised a cylindrical hammer and a cylindrical bit with the same characteristic impedance. The bit was terminated with a wedge. In front of the wedge there was a heavy block of concrete. The length of the bit and the initial gap between bit and concrete were varied systematically. The force versus penetration relationship and the work of fragmentation were determined in each test using a new technique based on measurement of strains at two cross-sections of the bit. Each test was simulated individually using a previously developed one-dimensional model. The results of simulations and experimental tests were found to agree well.

  • 10.
    Kou, S-Q
    et al.
    University of Science and Technology Beijing, Beijing, China.
    Rustan, Agne
    Luleå University of Technology.
    Burden related to blasthole diameter in rock blasting1992In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 29, no 6, p. 543-553Article in journal (Refereed)
    Abstract [en]

    Since the 1950s, most of the empirical formulas in rock blasting have incorporated a linear relation between burden and blasthole diameter. Recently it has been shown that a non-linear relation is more accurate for blasthole diameters in 40-400 mm range. This relation is different for surface and underground mines. In this paper, a complete relation between burden and either blasthole diameter or specific charge is established. This relation is based on energy conservation in single hole blast and consists of three terms which are related to surface energy for the two side cracks, fragmentation for the rock prism released and energy needed to move the rock. Four approximate formulas describing burden as a power function of the blasthole diameter are derived from the complete relation and dimensional analysis. The exponents of the diameter in the formulas are 2, 1, 5/6 and 2/3 and these decrease with the increasing scale in blasting. The coefficients of the power formulas are expressed as functions of the physical properties of the rock and explosive. The linear relation, derived as a special case with comparatively small blasthole diameters, is in a good agreement with Langefors' well-known formula. The valid ranges of the new formulas depend on the rock properties. The formulas were tested against the regression curves from real values in surface and underground mines and the results were better than those obtained using empirical methods.

  • 11. Li, Chunlin
    et al.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Assessment of damage in rock using the Kaiser effect of acoustic emission1993In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 30, no 7, p. 943-946Article in journal (Refereed)
    Abstract [en]

    The aim of our study is to explore the possibility of using the Kaiser effect method to assess damage in rock induced by blasting. Cores were drilled from a hard rock tunnel. The specimens prepared from the cores were uniaxially compressed in the laboratory and the AE from the specimens was recorded. The AE onset stress was taken as a measure of the damage in the rock induced by blasting. The results showed that the AE onset stress decreased with the distance from the tunnel floor. The extent of disturbance due to blasting could be estimated using the curve of the AE onset stress.

  • 12.
    Li, Chunlin
    et al.
    Department of Mining Engineering, Central South University of Technology, Changsha, China.
    Wai, Yuboo
    Department of Mathematics & Mechanics, Central South University of Technology, Changsha, China.
    Fracture toughness determination for marble using a round bar specimen1990In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 27, no 1, p. 71-75Article in journal (Refereed)
  • 13.
    Lindqvist, Per-Arne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Lai, Hai-Hui
    Central South Institute of Mining and Metallurgy, Changsha, Hunan.
    Alm, Ove
    Luleå University of Technology.
    Indentation fracture development in rock continuously observed with scanning electron microscope1984In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 21, no 4, p. 165-182Article in journal (Refereed)
    Abstract [en]

    Indentation tests observed in a scanning electron microscope (SEM) using a sharp and a truncated wedge in three different rocks are reported. By indenting at the edge of one surface and scanning the neighboring surface perpendicular to the direction of loading, it was possible to study the continuous development of cracks throughout the tests. Cracks initiated mainly at the edge and corners of wedges but initiation in the interior of the rock was also observed. Crack initiation and crack paths observed in all rocks are in good agreement with assumed theoretical elastic stress fields, although the nature of the fractures is greatly influenced by different material properties such as grain size, cleavage planes and grain bonding. Recorded force-displacement curves allowed distinction between different fracture processes.

  • 14.
    Ljunggren, Christer
    et al.
    Luleå University of Technology.
    Amadei, B.
    University of Colorado.
    Estimation of virgin rock stresses from horizontal hydrofractures1989In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 26, no 1, p. 69-78Article in journal (Refereed)
    Abstract [en]

    This paper presents an alternative theory for the determination of in situ stresses from hydraulic fracturing tests when the hydrofractures are either vertical or horizontal. The theory uses the E. Hoek and E.T. Brown criterion instead of the maximum tensile stress failure criterion. For horizontal fractures, the theory can be used to determine the difference in magnitude between the horizontal stress components and their domains of variation. In addition to the breakdown and shut-in pressures, obtained from the hydraulic fracturing tests, the theory requires knowledge of the unconfined compressive strength, the Poisson's ratio of the rock and one empirical constant, associated with the Hoek and Brown failure criterion or, alternatively, the tensile strength of the rock. The new theory is used to analyze the data from hydraulic fracturing tests at Lavia, Finland, where both vertical and horizontal hydrofractures were observed. Study results are discussed

  • 15.
    Ljunggren, Christer
    et al.
    Luleå University of Technology.
    Raillard, G.
    Luleå University of Technology.
    Rock stress measurements by means of hydraulic tests on pre-existing fractures at Gidea test site, Sweden1987In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 24, no 6, p. 339-345Article in journal (Refereed)
    Abstract [en]

    In situ rock stress measurements were performed by means of hydraulic tests on pre-existing fractures (HTPF) at Gidea in northern Sweden. The paper presents a summary of the theory, technique and the results from these measurements. Hydraulic tests on pre-existing fractures were conducted in a vertical borehole, in which hydraulic fracturing rock stress measurements had been conducted earlier, and the state of stress was determined at depths from 90 to 270 m. Two- and three-dimensional solutions of stress vs depth are presented, giving similar results, both in the magnitude and orientation of stresses. At depths between 100 and 150 m, the stress state is almost isotropic in a plane perpendicular to the borehole axis. A rotation of the maximum horizontal stress with depth was found. A comparison has been made between HTPF results and those obtained by conventional hydraulic fracturing

  • 16.
    Lundberg, Bengt
    Luleå University of Technology.
    A split Hopkinson bar study of energy absorption in dynamic rock fragmentation1976In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 13, no 6, p. 187-197Article in journal (Refereed)
    Abstract [en]

    Fragmentation of unconfined cylindrical specimens of rock due to stress wave loading has been investigated using a Split Hopkinson Bar (SHB). Photographs were taken during the fracture process using a high-speed framing camera, and incident, reflected and transmitted stress pulses were recorded using a digital transient recorder. The energy absorbed by the specimen during the fragmentation process was evaluated from the recorded stress pulses. Two different rocks were studied, namely Bohus granite and Solenhofen limestone. The specimen length was 50 mm, and the diameter was 25 mm. The incident pulse durations were 50, 100 and 200 μs, and the amplitude was in the range of 0·5-4 kbar. The high-speed photographs show that fracture occurs as previously observed for other rocks using SHB-devices. Notably, the main crack orientation is axial, and the degree of fragmentation increases with increasing load. The energy absorption of the specimen increases markedly when the load applied approaches a certain value. For the Bohus granite specimens the critical load was found to be 1·8 times the static compressive strength, and for Solenhofen limestone it was 1·3 times the static compressive strength. Two simple specimen models were analyzed theoretically, namely, one linearly-elastic and one rigid-plastic. The first model gives the best agreement with experimental results if the degree of fragmentaion is low, the second model gives the best agreement if the degree of fragmentation is high. The rigid-plastic model explains the experimental observation that the specimen always absorbs less than half the incident pulse energy.

  • 17.
    Lundberg, Bengt
    Luleå University of Technology.
    Efficiency of percussive drilling with extension rods1987In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 24, no 4, p. 213-222Article in journal (Refereed)
    Abstract [en]

    Extension drilling of rock is simulated numerically using a Victor desk-top computer. The hammer, adapter and extension rods are uniform and have the same characteristics impedances. The same is true for the joints and the bit. Two efficiencies are determined as functions of six dimensionless parameters which represent the number of joints, the joint-to-hammer length ratio, the joint-to-rod characteristic impedance ratio, the initial gap between bit and rock and the bit/rock interaction (two parameters). The first efficiency is defined as the ratio of the work performed on the rock to the impact kinetic energy of the hammer. The second is based on the sum of the work performed on the rock and the rebound kinetic energy of the hammer, which is assumed to be fully retrieved. Both efficiencies generally decrease with the number of joints and the joint-to-hammer length ratio. Exceptionally, however, the efficiencies may increase slightly with the number of joints. The difference between the second and first efficiency, which is due to hammer rebound, generally increases when the rock becomes increasingly hard. This dependence on rock hardness is strongest when the number of joints and the joint-to-hammer length ratio are low. In the absence of joints the efficiencies have an oscillatory dependence on a small initial gap. When one or several joints are used, however, the efficiencies essentially decrease with the initial gap.

  • 18.
    Lundberg, Bengt
    Luleå University of Technology.
    Microcomputer simulation of percussive drilling1985In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 22, no 4, p. 237-249Article in journal (Refereed)
    Abstract [en]

    Churn drilling, down-the-hole drilling, hammer drilling, and related drilling and breaking processes are simulated by means of a microcomputer. The simulation programs are written in Apple Pascal for the Apple II family of computers. Accounts are given of the simulation programs and their theoretical basis, and results are presented from two different simulation studies. The first study concerns the efficiency of a simple percussive system which consists of a cylindrical hammer and a cylindrical bit, both with the same characteristic impedance. The second simulation study concerns a commercial percussive drill, namely, Atlas Copco's COP 1038 HD. For both simulation studies, comparisons are made with exact theoretical results

  • 19.
    Lundberg, Bengt
    Luleå University of Technology.
    Microcomputer simulation of stress wave energy transfer to rock in percussive drilling1982In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 19, no 5, p. 229-239Article in journal (Refereed)
    Abstract [en]

    Microcomputer "Apple II Plus" is used. Drilling model is based on the theory of non-dimensional stress wave for borer and cutter and on non-linear relation between force and penetration for interaction of cutting/rock formation. The propagation of wave is visualized. Graphics of force/terrain is displayed on oscilloscope. The wearing of the cutter by drilling is studied. Mass is more important than the form of the cutter.

  • 20.
    Lundberg, Bengt
    et al.
    Luleå University of Technology.
    Karlsson, L.G.
    Luleå University of Technology.
    Influence of geometrical design on the efficiency of a simple down-the-hole percussive drill1986In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 23, no 3, p. 281-287Article in journal (Refereed)
    Abstract [en]

    In the present investigation, the simulation program DTH-SIM is used to determine the efficiency of a simple down-the-hole percussive drill, which has the main features of a practical design. The efficiency is obtained as a function of the same dimensionless parameters as in a preceding study of two additional parameters which represent the characteristic impedance and the length of the head of the bit. Several results obtained here for non-uniform bits differ considerably from those established previously for uniform bits

  • 21.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Effect of thrust on the performance of percussive rock drills1989In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 26, no 1, p. 51-59Article in journal (Refereed)
    Abstract [en]

    The performance of two different percussive rock drills has been studied theoretically by simulating the drilling process. The two drills studied correspond to an idealized drill and a more complex, prototype drill. The efficiency, the maximum stress (maximum tensile stress) and the minimum stress (maximum compressive stress) have been determined during the simulations. Also, the stability of the drill string with respect to buckling has been estimated as a function of a constant applied thrust. Two cases of applied thrust were simulated. They correspond to a constant applied thrust and an applied thrust with time dependent harmonic variations. The results show that for low frequency variations in thrust, the performance of the rock drill is almost the same as for a constant applied thrust. It was assumed in the remainder of this study that the applied thrust can be treated as a constant force. The results obtained for a constant applied thrust are summarized.

  • 22. Ouchterlony, Finn
    On the background to the formulae and the accuracy of rock fracture toughness measurements using ISRM standard core specimens1989In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 26, no 1, p. 13-23Article in journal (Refereed)
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  • 23. Ouchterlony, Finn
    Suggested methods for determining the fracture toughness of rock1988In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 25, no 2, p. 71-96Article in journal (Refereed)
  • 24.
    Stephansson, Ove
    Luleå University of Technology.
    Rock mechanics in Sweden1989In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 26, no 1, p. 1-11Article in journal (Refereed)
    Abstract [en]

    This paper reviews rock mechanics research activities in Sweden. A short history of the development of rock mechanics in the mining, underground construction and mining equipment industries is presented. Teaching at Swedish technical universities and activity in research organizations and in the Swedish National Group of the ISRM are outlined. For the next 5-10 yr, most of the applied rock mechanics research will be conducted in the fields of mining and the final disposal of radioactive waste. New fields in the application of rock mechanics are being developed, for example, gas storage in excavations of hard rocks. Tunnel boring in hard rocks, holography for rock monitoring during blasting, physical and numerical modelling of grouting and some new trends in rock stress measurements are presented as examples of present research work within the major research organizations and university departments in Sweden.

  • 25.
    Stephansson, Ove
    et al.
    Luleå University of Technology.
    Lande, G.
    Bjerking Ingenjörsbyrå AB, Uppsala, Sweden.
    Bodare, A.
    Bjerking Ingenjörsbyrå AB, Uppsala, Sweden.
    Seismic study of shallow jointed rocks1979In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 16, no 5, p. 319-327Article in journal (Refereed)
    Abstract [en]

    A theory of wave propagation in shallow jointed rocks is presented. The elastic waves from a source are propagated around the tip of an open joint. The depth of the joint is determined from known intercept times, wave velocities and joint spacing. The principles developed in this paper are compared with the theory of seismic refraction, and are verified in model experiments on artificial joints in concrete blocks.

    Field tests were made in an open pit and an underground mine. An explosive pulse exciter for generation of P- and SH-waves is described. The depth of jointing in the rock walls is determined by field observations and logging in bore holes, and the results confirm the theory.

  • 26.
    Sun, Z.
    et al.
    CSIRO Division of Building Research, Highett, Victoria.
    Gerrard, C.
    CSIRO Division of Building Research, Highett, Victoria.
    Stephansson, Ove
    Luleå University of Technology.
    Rock joint compliance tests for compression and shear loads1985In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 22, no 4, p. 197-213Article in journal (Refereed)
    Abstract [en]

    A series of compression and shear tests were conducted at large scale on joint surfaces in granite and slate specimens, with special equipment being used to isolate the deformations of the joints from those of the rock material. The matrix of compliance components for a rock joint is discussed in relation to these standard tests and it is shown that one pair of compliance components can be determined from a compression test and a second pair from a shear test. For the compression tests, the test results indicate a pattern of decreasing compliance with load, an increase in compliance with initial aperture, and high levels of recoverability of deformation. In the shear tests, the curves for the relative displacements indicate there are three zones of different behavior, elastic, transition and sliding

  • 27.
    Sun, Zongqi
    et al.
    Luleå University of Technology.
    Ouchterlony, Finn
    Swedish Detonic Research Foundation (SveDeFo), Stockholm, Sweden.
    Fracture toughness of stripa granite cores1986In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 23, no 6, p. 399-409Article in journal (Refereed)
    Abstract [en]

    There is a growing interest in the study of fracture parameters of rock material, but to date no standard testing method for measuring the fracture toughness of rock exists. Three round specimen configurations, namely the notched beam, the compact specimen, and the short rod were used in this work and different fracture toughness measures evaluated for Stripa granite. An approximate fracture toughness, Km, obtained without pre-cracking the specimens, was analysed statistically to indicate its dependence on notch length. Then a comparison with an apparent fracture toughness. KQm, obtained from precracked specimens, showed that low Km values arise because the microcrack growth that precedes crack extension is neglected.

    Acceptable KQm values, in the sense that they are good estimates of KIc, can be obtained from three point bending tests on 40 mm diameter drill cores with notches of about 12 mm depth. The fracture toughness from short rod tests was found to be size independent in this investigation, and the value consistent with KQm values from the compact tension and the three point bending tests. The ligament width was found to be a more critical size parameter than the crack length during the testing.

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  • 28.
    Suárez Del Rio, L.M.
    et al.
    Department of Petrology, Faculty of Geology, University of Oviedo, Oviedo, Spain.
    Norin, J.
    Luleå University of Technology.
    Bending tests and acoustic emission for heated avesta-gneiss1985In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 22, no 1, p. 47-50Article in journal (Refereed)
  • 29.
    Swan, G.
    Luleå University of Technology.
    Fracture stress scale effects for rocks in bending1980In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 17, no 6, p. 317-324Article in journal (Refereed)
    Abstract [en]

    The nature of fracture stress size dependency is examined for rocks in bending. After establishing the order of the dependency for unnotched specimens, notched specimens are then used so facilitating a fracture mechanics approach. Such an approach is found to better quantify fracture stress scale effects than the alternative approach of Weibull-type statistical arguments. The explanation for this is found to lie in the former's ability to take into account sub-critical growth effects prior to the fracture stress event in rocks.

  • 30.
    Yi, Xiaoping
    et al.
    Department of Mining, Central-South University of Technology, Changsha, Hunan, China.
    Sun, Zongqi
    Department of Mining, Central-South University of Technology, Changsha, Hunan, China.
    Ouchterlony, Finn
    Swedish Detonic Research Foundation, Stockholm, Sweden.
    Stephansson, Ove
    Division of Engineering Geology, Royal Institute of Technology, Stockholm, Sweden.
    Fracture toughness of Kallax gabbro and specimen size effect1991In: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 28, no 2/3, p. 219-223Article in journal (Refereed)
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