ALBERT

Description:    A major engineering challenge for mines experiencing significant seismicity is the performance of the support systems. This paper provides a critical review of dynamic testing techniques used for understanding and quantifying the performance of ground support systems. This review focuses on testing rigs in Canada, Australia and South Africa. The different laboratory testing rigs are listed along with their characteristics and their advantages and disadvantages. The paper concludes with recommendations towards developing a more unified strategy to understand and eventually forecast the behaviour of support systems under dynamic loads. Content Type Journal Article Pages 1-14 DOI 10.1007/s00603-011-0155-4 Authors John Hadjigeorgiou, Lassonde Institute for Mining, University of Toronto, Room 121, 170 College Street, Toronto, ON, M5S 3E3, Canada Yves Potvin, Australian Centre for Geomechanics, P O Box 3296, Broadway, Nedlands, WA 6009, Western Australia Journal Rock Mechanics and Rock Engineering Online ISSN 1434-453X Print ISSN 0723-2632

Description:    The effect of specimen size on the measured unconfined compressive strength and other mechanical properties has been studied by numerous researchers in the past, although much of this work has been based on specimens of non-standard dimensions and shapes, and over a limited size range. A review of the published literature was completed concentrating on the presentation of research pertaining to right cylindrical specimens with height:diameter ratios of 2:1. Additionally, new data has been presented considering high strength (70 MPa) cement mortar specimens of various diameters ranging from 63 to 300 mm which were tested to failure. Currently, several models exist in the published literature that seek to predict the strength–size relationship in rock or cementitious materials. Modelling the reviewed datasets, statistical analysis was used to help establish which of these models best represents the empirical evidence. The findings presented here suggest that over the range of specimen sizes explored, the MFSL (Carpinteri et al. in Mater Struct 28:311–317, 1995 ) model most closely predicts the strength–size relationship in rock and cementitious materials, and that a majority of the empirical evidence supports an asymptotic value in strength at large specimen diameters. Furthermore, the MFSL relationship is not only able to model monotonically decreasing strength–size relationships but is also equally applicable to monotonically increasing relationships, which although shown to be rare do for example exist in rocks with fractal distributions of hard particles. Content Type Journal Article Pages 1-17 DOI 10.1007/s00603-011-0161-6 Authors William J. Darlington, Department of Civil Engineering, Monash University, Clayton, VIC, Australia Pathegama G. Ranjith, Department of Civil Engineering, Monash University, Clayton, VIC, Australia S. K. Choi, CSIRO Earth Science and Resource Engineering, Bayview Avenue, Clayton, VIC, Australia Journal Rock Mechanics and Rock Engineering Online ISSN 1434-453X Print ISSN 0723-2632

Description: Comments on “Estimating the Strength of Jointed Rock Masses” by Lianyang Zhang Content Type Journal Article Pages 1-6 DOI 10.1007/s00603-011-0152-7 Authors Ergin Arıoğlu, Yapı Merkezi R&D Department, Hacı Resit Pasa Sok. No:7, Camlıca, 34676 Istanbul, Turkey Gözde Kurt, Yapı Merkezi R&D Department, Hacı Resit Pasa Sok. No:7, Camlıca, 34676 Istanbul, Turkey Sanem Kayalı, Yapı Merkezi R&D Department, Hacı Resit Pasa Sok. No:7, Camlıca, 34676 Istanbul, Turkey Journal Rock Mechanics and Rock Engineering Online ISSN 1434-453X Print ISSN 0723-2632

Description:    An exact closed form solution is derived for the mechanical behaviour of a linear viscoelastic Burgers rock around an axisymmetric tunnel, supported by a linear elastic ring. Analytical formulae are provided for the displacement of the rock/lining interface and for the pressure exerted by the rock on the lining, taking into account the stiffness and its installation time. Results calculated from these formulae do validate the corresponding numerical results of a 2D finite differences code. Further, comparison to previous existing solutions for the same viscoelastic model indicates similarities and differences. A parametric study is performed to investigate the effect of the viscoelastic constants, the stiffness and installation time of the support. The derived closed form solution is used to construct the time-dependent Supported Ground Reaction Curves of the viscoelastic rock, i.e. the time contour plots on the convergence confinement diagram. The importance of the effect of the support on the restrained rock creep and the exerted pressure on the lining, during the design life of a structure, is examined. Content Type Journal Article Pages 1-12 DOI 10.1007/s00603-011-0159-0 Authors Pavlos Nomikos, Division of Mining Engineering, School of Mining and Metallurgy, National Technical University, 9 Iroon Polytechneiou St, Zografou, 157 80 Athens, Greece Reza Rahmannejad, Mining Department, Shahid Bahonar University of Kerman-Iran, Kerman, Iran Alexandros Sofianos, Division of Mining Engineering, School of Mining and Metallurgy, National Technical University, 9 Iroon Polytechneiou St, Zografou, 157 80 Athens, Greece Journal Rock Mechanics and Rock Engineering Online ISSN 1434-453X Print ISSN 0723-2632

Description:    Based on the geometric analysis of the relationship between the stress state at a point and the yield surface defined in the principal stress space, a coefficient ω is set up as an estimation index to describe the stress-induced yield risk. After yield, the equivalent plastic shear strains is usually used to characterize the failure degree (FD) of the material and adopted here as an index of the damage degree for the surrounding rock masses. Then, a unified variable combining ω and FD, named failure approaching index (FAI), is constructed to estimate the stability of rock mass which may be at different deformation stages. The formulas of FAI are derived for some popular yield criteria in geomechanics. Details for such development are addressed in the paper. Its rationality is verified by numerical simulation and comparative analysis of the conventional triaxial compression tests and typical tunnel projects. In addition, the method for applying FAI to the stability estimation of surrounding rock mass is proposed. As examples, the stability of the underground powerhouse, access tunnels and headrace tunnels at the Jinping II hydropower station are estimated by making use of the method we presented. The results indicate that not only is the index rational in mechanics, but the theory also has good expansibility, and the estimation methods are simple and practical as well. It is easier for field engineers to analyze and understand the numerical results. Content Type Journal Article Pages 1-14 DOI 10.1007/s00603-011-0150-9 Authors C. Q. Zhang, State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, 430071 People’s Republic of China H. Zhou, State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, 430071 People’s Republic of China X. T. Feng, State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, 430071 People’s Republic of China Journal Rock Mechanics and Rock Engineering Online ISSN 1434-453X Print ISSN 0723-2632

Description:    This paper presents the results of a case study performed in Well BT-1 in the Blacktip field; an offshore field located in northern Australia. An analytical model based on mud logging data was used to estimate a formation’s strength in Well BT-1. The drilled well is vertical and the input data to the model included the rate of penetration, rotary speed, weight on bit and torque values of the bit obtained from mud logging data. The final model was completed in several steps: estimation of the bit constants from either lab or field data, backward calculation of rock strength using a drilling performance model, smoothing of the estimated log to obtain the apparent rock strength log and classifying the formations into zones with similar strength values. The results of a log-based approach carried out in Well BT-1 were used to do the modelling. The results presented here indicate that the drilling performance model is able to predict the formation strength reasonably well. Based on the results, care should be taken when the model is used for the intervals where the bit is worn and dull, since within these intervals the model tends to over-estimate the rock strength. Content Type Journal Article Pages 1-12 DOI 10.1007/s00603-011-0142-9 Authors Masood Mostofi, Department of Petroleum Engineering, Curtin University, Perth, WA Australia Vamegh Rasouli, Department of Petroleum Engineering, Curtin University, Perth, WA Australia Elike Mawuli, ENI Australia Limited, Perth, WA Australia Journal Rock Mechanics and Rock Engineering Online ISSN 1434-453X Print ISSN 0723-2632

Description: Reply to the Discussion by Arıoglu et al. on “Estimating the Strength of Jointed Rock Masses” by Zhang, DOI 10.1007/s00603-009-0065-x Content Type Journal Article Pages 1-1 DOI 10.1007/s00603-011-0154-5 Authors Lianyang Zhang, Department of Civil Engineering and Engineering Mechanics, University of Arizona, Tucson, AZ, USA Journal Rock Mechanics and Rock Engineering Online ISSN 1434-453X Print ISSN 0723-2632

Description: Discussion on the Paper Entitled “On a Paradox of Elasto-Plastic Tunnel Analysis” by L. Cantieni and G. Anagnostou, Published in Rock Mechanics and Rock Engineering (2011) 44:129–147 Content Type Journal Article Category Discussion Pages 1-2 DOI 10.1007/s00603-011-0178-x Authors Shunsuke Sakurai, Construction Engineering Research Institute Foundation, 1-3-10, Tsurukabuto, Nada-ku, Kobe, 657-0011 Japan Journal Rock Mechanics and Rock Engineering Online ISSN 1434-453X Print ISSN 0723-2632

Description:    In this paper, white Portland cement was used as an experimental material. Prismatic specimens with pre-existing flaws at different angles of inclination ( α ) varying through 0°, 30°, 45°, 60°, 75° to 90° and cylindrical specimens with different numbers of pre-existing flaws ( n ) varying through 0, 1, 2 to 3 were tested under uni-axial compression tests. Crack initiation, propagation, coalescence, and failure were observed. The corresponding analytical expression for the stress intensity factor under uni-axial compression was derived, the coefficient of friction and the stress intensity factor of the specimens on the surfaces of the crack were analysed, and the corrective coefficient for the stress intensity factor was introduced. Fatigue tests with a loading frequency of f  = 100 Hz were carried out on cylindrical specimens with constant amplitude of the cyclic load which is a proportion of the compressive load at failure ( F f ) obtained from the uni-axial compression tests. The fatigue property of the specimens was analysed and the relationship ( S max  − lg  N f ) between the maximum stress and the number of loading cycles at failure for specimens with pre-existing flaws was proposed. The effect of pre-existing flaws on the fatigue life ( N f ) and dynamic load ( S D ) which can be applied was investigated. Content Type Journal Article Category Original Paper Pages 1-9 DOI 10.1007/s00603-011-0186-x Authors Y. L. Chen, Department of Civil Engineering, University of Shanghai for Science and Technology, 516 Jungong Road, Shanghai, 200093 People’s Republic of China J. Ni, Department of Civil Engineering, University of Shanghai for Science and Technology, 516 Jungong Road, Shanghai, 200093 People’s Republic of China W. Shao, Department of Civil Engineering, University of Shanghai for Science and Technology, 516 Jungong Road, Shanghai, 200093 People’s Republic of China Y. C. Zhou, Department of Civil Engineering, University of Shanghai for Science and Technology, 516 Jungong Road, Shanghai, 200093 People’s Republic of China A. Javadi, Department of Engineering, University of Exeter, North Park Road, Exeter, EX4 4QF UK R. Azzam, Department of Engineering Geology and Hydrogeology, RWTH Aachen University, Lochnerstr. 4-20, 52064 Aachen, Germany Journal Rock Mechanics and Rock Engineering Online ISSN 1434-453X Print ISSN 0723-2632

Description: Response by the Authors to S. Sakurai’s Discussion of the Paper “On a Paradox of Elasto-Plastic Tunnel Analysis” Content Type Journal Article Category Discussion Pages 1-4 DOI 10.1007/s00603-011-0188-8 Authors G. Anagnostou, ETH Zurich, 8093 Zurich, Switzerland L. Cantieni, ETH Zurich, 8093 Zurich, Switzerland Journal Rock Mechanics and Rock Engineering Online ISSN 1434-453X Print ISSN 0723-2632