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 ...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.展开更多
This work presents particle-based numerical simulations on coal pillars in a coal mine based underground water reservoir(CMUWR).We aim to replicate the stress-strain characteristics and present the acoustic emission b...This work presents particle-based numerical simulations on coal pillars in a coal mine based underground water reservoir(CMUWR).We aim to replicate the stress-strain characteristics and present the acoustic emission behavior of the coal under complex dynamic stress paths.The study reveals failure characteristics of coal exposed to monotonic/cyclic shear load under constant/cyclic normal loads.Based on the evolution of stress-time-dependent bond diameter implemented in particle model,different damage paths are established for dry and water-immersed samples under two loading frequencies.Furthermore,the numerical Gutenberg-Richter's b-value was calculated from the released energy emanating from bond failure,and this work presents the evolution of numerical Gutenberg-Richter's b-value.The numerical simulation contributes to a micromechanical understanding of the failure mechanisms of coal under water-immersion and cyclic stress,providing valuable insights for strength prediction of CMUWR.展开更多
基金Rio Tinto for sponsoring much of the work outlined in this article through the Rio Tinto Centre for Underground Mine Construction (an affiliate of CEMI)the financial contributions of NSERC (Natural Sciences and Engineering Research Council of Canada)
文摘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.
基金funded by Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining(GJNY-20-113-03)Funds from NSFC(52204086)+2 种基金Funds from Joint National-Local Engineering Research Center for Safe and Precise Coal Mining(EC2021004)Funds from State Key Laboratory of Coal Resources in Western China(SKLCRKF20-07)Fund from Alexander von Humboldt Stiftung.
文摘This work presents particle-based numerical simulations on coal pillars in a coal mine based underground water reservoir(CMUWR).We aim to replicate the stress-strain characteristics and present the acoustic emission behavior of the coal under complex dynamic stress paths.The study reveals failure characteristics of coal exposed to monotonic/cyclic shear load under constant/cyclic normal loads.Based on the evolution of stress-time-dependent bond diameter implemented in particle model,different damage paths are established for dry and water-immersed samples under two loading frequencies.Furthermore,the numerical Gutenberg-Richter's b-value was calculated from the released energy emanating from bond failure,and this work presents the evolution of numerical Gutenberg-Richter's b-value.The numerical simulation contributes to a micromechanical understanding of the failure mechanisms of coal under water-immersion and cyclic stress,providing valuable insights for strength prediction of CMUWR.
