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Strength of massive to moderately jointed hard rock masses

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第3期11卷 562-575页

作者： R.P.Bewick P.K.Kaiser F.Amann Golder Associates Ltd. 33 Mackenzie StreetSudburyOntarioP3C 4Y1Canada Laurentian University 935 Ramsey Lake RdSudburyP3E 2C6Canada RWTH Aachen Lochnerstrasse Aachen4-20D-52064Germany

The Hoek-Brown (HB) failure criterion and the geological strength index (GSI) were developed for the estimation of rock mass strength in jointed and blocky ground where rock mass failure is dominated by sliding along open joints and rotation of rock blocks. In massive, veined and moderately jointed rock in which rock blocks cannot form without failure of intact rock, the approach to obtain HB parameters must be modified. Typical situations when these modifications are required include the design of pillars, excavation and cavern stability, strainburst potential assessment, and tunnel support in deep underground conditions (around σ1/σci > 0.15, where σ1 is the major principal compressive stress and σci is the unconfined compressive strength of the homogeneous rock) in hard brittle rocks with GSI ≥ 65. In this article, the strength of massive to moderately jointed hard rock masses is investigated, and an approach is presented to estimate the rock mass strength envelope using laboratory data from uniaxial and triaxial compressive strength tests without reliance on the HB-GSI equations. The data from tests on specimens obtained from massive to moderately jointed heterogeneous (veined) rock masses are used to obtain the rock and rock mass strengths at confining stress ranges that are relevant for deep tunnelling and mining;and a methodology is presented for this purpose from laboratory data alone. By directly obtaining the equivalent HB rock mass strength envelope for massive to moderately jointed rock from laboratory tests, the HB-GSI rock mass strength estimation approach is complemented for conditions where the GSIequations are not applicable. Guidance is also provided on how to apply the proposed approach when laboratory test data are not or not yet available.

关键词： Brittle rock Uniaxial compressive strength(UCS) Geological strength index(GSI) Massive to moderately jointed rock masses

Deformation-based support design for highly stressed ground with a focus on rockburst damage mitigation

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第1期14卷 50-66页

作者： P.K.Kaiser A.Moss Laurentian University SudburyONP3E 2C6Canada GeoK Inc.680 Ramsey Lake Road SudburyONP3E 6H5Canada Sonal Mining Technology Inc. 2488 Shadbolt LaneWest VancouverBCV7S 3J1Canada

As mines go deeper,mine designs become more fragile and effective rock support becomes a strategic element for ground control to facilitate timely construction and cost-effective access for uninterrupted *** article focuses on the design of integrated support systems for brittle ground when large displacements due to gradual bulking of stress-fractured rock or sudden violent bulking during rockbursts are induced by static and dynamic *** provides an overview of support design principles for a rational approach to ground control in deep mines when large deformations are anticipated near *** designs must not only account for load equilibrium but also for deformation *** importantly,the design approach must account for the fact that the support’s displacement capacity is being consumed as it is deformed after support *** is therefore necessary to design for the remnant support capacity,*** capacity remaining when the support is ***,if the support capacity can be consumed,it can also be restored by means of preventive support maintenance(PSM).The PSM concept for cost-effective ground control is introduced and illustrated by quantitative and operational *** to other design approaches,the deformation-based support design(DBSD)approach provides the capacity of an integrated support system as a function of imposed *** in this support capacity due to mininginduced deformation renders excavations increasingly more vulnerable if located within the influence of active mining and seismic *** deformation measurements are robust indicators of the decay in support capacity,scanning and other displacement monitoring technologies enable measurements to verify the DBSD approach,to assess the remnant safety margin of the deformed support,and to make operational support maintenance decisions.

关键词： Deep mining Deformation-based support design(DBSD) Cost-effective support Support consumption Preventive support maintenance(PSM)

Verification of a laboratory-based dilation model for in situ conditions using continuum models

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Journal of Rock Mechanics and Geotechnical Engineering 2014年第6期6卷 522-534页

作者： G.Walton M.S.Diederichs L.R.Alejano J.Arzúa Queen's University Kingston Canada University of Vigo Vigo Spain

With respect to constitutive models for continuum modeling applications, the post-yield domain remainsthe area of greatest uncertainty. Recent studies based on laboratory testing have led to thedevelopment of a number of models for brittle rock dilation, which account for both the plastic shearstrain and confining stress dependencies of this phenomenon. Although these models are useful inproviding an improved understanding of how dilatancy evolves during a compression test, there hasbeen relatively little work performed examining their validity for modeling brittle rock yield in situ. Inthis study, different constitutive models for rock dilation are reviewed and then tested, in the context of anumber of case studies, using a continuum finite-difference approach （FLAC）. The uncertainty associatedwith the modeling of brittle fracture localization is addressed, and the overall ability of mobilizeddilation models to replicate in situ deformation measurements and yield patterns is evaluated. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

关键词： Dilation Continuum models Case studies Brittle rock

Analysis of rockburst in tunnels subjected to static and dynamic loads

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第6期9卷 1031-1040页

作者： Amin Manouchehrian Ming Cai Bharti School of Engineering Laurentian University Sudbury P3E 2C6 Canada MIRARCO Laurentian University 935 Ramsey Lake Road Sudbury P3E 2C6 Canada State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences Wuhan 430071Hubei China

The presence of geological structures such as faults, joints, and dykes has been observed near excavation boundaries in many rockburst case histories. In this paper, the role of discontinuities around tunnels in rockburst occurrence was studied. For this purpose, the Abaqus explicit code was used to simulate dynamic rock failure in deep tunnels. Material heterogeneity was considered using Python scripting in Abaqus. Rockbursts near fault regions in deep tunnels under static and dynamic loads were *** tunnel models with and without faults were built and static and dynamic loads were used to simulate rock failure. The velocity and the released kinetic energy of failed rocks, the failure zone around the tunnel, and the deformed mesh were studied to identify stable and unstable rock failures. Compared with models without discontinuities, the results showed that the velocity and the released kinetic energy of failed rocks were higher, the failure zone around the tunnel was larger, and the mesh was more deformed in the models with discontinuities, indicating that rock failure in the models with discontinuities was more violent. The modeling results confirm that the presence of geological structures in the vicinity of deep excavations could be one of the major influence factors for the occurrence of rockburst. It can explain localized rockburst occurrence in civil tunnels and mining drifts. The presented methodology in this paper for rockburst analysis can be useful for rockburst anticipation and control during mining and tunneling in highly stressed ground.

关键词： Rockburst Numerical modeling Geological structure Static load increase Dynamic disturbance Tunnel

Design of rock support system under rockburst condition

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Journal of Rock Mechanics and Geotechnical Engineering 2012年第3期4卷 215-227页

作者： Peter K. Kaiser Centre for Excellence in Mining Innovation Sudbury Ontario Canada

As mining and civil tunneling progresses to depth, excavation-induced seismicity and rockburst problems increase and cannot be prevented. As an important line of defense, ground control measures and burst-resistant rock support are used to prevent or minimize damage to excavations and thus to enhance workplace safety. Rock support in burst-prone ground differs from conventional rock support where controlling gravity-induced rockfalls and managing shallow zones of loose rock are the main target. Rock support in burst-prone ground needs to resist dynamic loads and large rock dilation due to violent rock failure. After reviewing the rockburst phenomenon, types of rockbursts, damage mechanisms, and rockburst support design principles and acceptability criteria, this paper describes that the support selection process in burst-prone ground is iterative, requiring design verification and modification based on field observations. An interactive design tool for conducting rockburst support design in underground tunnels is introduced to facilitate cost-effective design.

关键词： rockburst rockburst damage rock support design

Spectral-element simulations of elastic wave propagation in exploration and geotechnical applications

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Earthquake Science 2014年第2期27卷 179-187页

作者： Lin Zheng Qi Zhao Bernd Milkereit Giovanni Grasselli Qinya Liu Department of Physics University of Toronto Department of Civil Engineering University of Toronto Department of Earth Sciences University of Toronto

We apply the spectral-element method（SEM）,a high-order finite-element method（FEM） to simulate seismic wave propagation in complex media for exploration and geotechnical problems. The SEM accurately treats geometrical complexities through its flexible FEM mesh and accurately interpolates wavefields through high-order Lagrange polynomials. It has been a numerical solver used extensively in earthquake seismology. We demonstrate the applicability of SEM for selected 2D exploration and geotechnical velocity models with an open-source SEM software package SPECFEM2D. The first scenario involves a marine survey for a salt dome with the presence of major internal discontinuities,and the second example simulates seismic wave propagation for an open-pit mine with complex surface topography. Wavefield snapshots,synthetic seismograms,and peak particle velocity maps are presented to illustrate the promising use of SEM for industrial problems.

关键词： Seismic wave propagation Spectral-element method Exploration seismology

Influence of degree of interlock on confined strength of jointed hard rock masses

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第6期12卷 1152-1170页

作者： Navid Bahrani Peter K.Kaiser a Department of Civil and Resource Engineering Dalhousie UniversityHalifaxNova ScotiaCanada b Bharti School of Engineering Laurentian UniversitySudburyOntarioCanada

The strength of jointed rock mass is strongly controlled by the degree of interlock between its constituent rock *** degree of interlock constrains the kinematic freedom of individual rock blocks to rotate and slide along the block forming *** HoekeBrown(HB)failure criterion and the geological strength index(GSI)were developed based on experiences from mine slopes and tunneling projects in moderately to poorly interlocked jointed rock *** has since then been demonstrated that the approach to estimate the HB strength parameters based on the GSI strength scaling equations(called the‘GSI strength equations’)tends to underestimate the confined peak strength of highly interlocked jointed rock masses(***>65),where the rock mass is often non-persistently jointed,and the intact rock blocks are strong and *** estimation of the confined strength of such rock masses is relevant when designing mine pillars and abutments at great depths,where the confining pressure is high enough to prevent block rotation and free sliding on block *** this article,a grain-based distinct element modeling approach is used to simulate jointed rock masses of various degrees of interlock and to investigate the influences of block shape,joint persistence and joint surface condition on the confined peak *** focus is on non-persistently jointed and blocky(persistently jointed)rock masses,consisting of hard and homogeneous rock blocks devoid of any strength degrading defects such as *** results from this investigation confirm that the GSI strength equations underestimate the confined strength of highly interlocked and non-persistently jointed rock ***,the GSI strength equations are found to be valid to estimate the confined strength of persistently jointed rock masses with smooth and non-dilatant joint surfaces.

关键词： Rock mass strength Degree of interlock Non-persistently jointed rock mass Blocky rock mass Geological strength index(GSI) GSI strength equations

Large-Scale Electromagnetic Modeling for Multiple Inhomogeneous Domains

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Communications in Computational Physics 2009年第7期6卷 269-289页

作者： Masashi Endo Martin Cuma Michael S.Zhdanov Department of Geology and Geophysics University of Utah135S 1460ERm 719Salt Lake CityUT 84112USA

We develop a new formulation of the integral equation(IE)method for three-dimensional(3D)electromagnetic(EM)field computation in large-scale models with multiple inhomogeneous *** problem arises in many practical applications including modeling the EM fields within the complex geoelectrical structures in geophysical *** geophysical applications,it is difficult to describe an earth structure using the horizontally layered background conductivity model,which is required for the efficient implementation of the conventional IE *** a result,a large domain of interest with anomalous conductivity distribution needs to be discretized,which complicates the *** new method allows us to consider multiple inhomogeneous domains,where the conductivity distribution is different from that of the background,and to use independent discretizations for different *** reduces dramatically the computational resources required for largescale *** addition,using this method,we can analyze the response of each domain separately without an inappropriate use of the superposition principle for the EM field *** method was carefully tested for the modeling the marine controlled-source electromagnetic(MCSEM)fields for complex geoelectric structures with multiple inhomogeneous domains,such as a seafloor with the rough bathymetry,salt domes,and *** have also used this technique to investigate the return induction effects from regional geoelectrical structures,e.g.,seafloor bathymetry and salt domes,which can distort the EM response from the geophysical exploration target.

关键词： Large-scale EM modeling multiple inhomogeneous domains marine CSEM