Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this cha...Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this challenge,nonlinear stress boundaries for a numerical model are determined through regression analysis of a series of nonlinear coefficient matrices,which are derived from the bubbling method.Considering the randomness and flexibility of the bubbling method,a parametric study is conducted to determine recommended ranges for these parameters,including the standard deviation(σb)of bubble radii,the non-uniform coefficient matrix number(λ)for nonlinear stress boundaries,and the number(m)and positions of in situ stress measurement points.A model case study provides a reference for the selection of these parameters.Additionally,when the nonlinear in situ stress inversion method is employed,stress distortion inevitably occurs near model boundaries,aligning with the Saint Venant's principle.Two strategies are proposed accordingly:employing a systematic reduction of nonlinear coefficients to achieve high inversion accuracy while minimizing significant stress distortion,and excluding regions with severe stress distortion near the model edges while utilizing the central part of the model for subsequent simulations.These two strategies have been successfully implemented in the nonlinear in situ stress inversion of the Xincheng Gold Mine and have achieved higher inversion accuracy than the linear method.Specifically,the linear and nonlinear inversion methods yield root mean square errors(RMSE)of 4.15 and 3.2,and inversion relative errors(δAve)of 22.08%and 17.55%,respectively.Therefore,the nonlinear inversion method outperforms the traditional multiple linear regression method,even in the presence of a systematic reduction in the nonlinear stress boundaries.展开更多
Accurately reconstructing rock structures using numerical methods is vital in rock mechanics research community,especially when obtaining rock samples is difficult and expensive.The reconstructed models must reflect t...Accurately reconstructing rock structures using numerical methods is vital in rock mechanics research community,especially when obtaining rock samples is difficult and expensive.The reconstructed models must reflect the comprehensive characteristics of natural rock,including mineral content and spatial distributions.This study employs the bubbling method to reconstruct granite containing multiple minerals in both two-(2D)and three-dimensions(3D),proposing a general procedure for granite structure reconstruction.The bubbling method utilizes numerous bubbles(hemispheres or spheres)of varying sizes and gradually changing properties,which are randomly overlapped to create a heterogeneous plane(2D)or space(3D).The properties of these overlapped areas are adjusted based on the sum of neighboring bubbles'properties,allowing specific regions with extreme properties to be selected and intercepted to form the desired mineral shapes.The results demonstrate that the reproduced granite samples can accurately exhibit the mineral distributions and sizes of real granite,quantified by fractal dimension(D)and the hourglass parameter(V_(Sum)=V_(Total)).The proposed method is also suitable for reconstructing anisotropic granite models,with anisotropy described by a fitted elliptic curve derived from ratios between directional mineral sizes and cross-sectional dimensions.Based on these findings,a series of numerical granite models with similar structures were reconstructed and tested.Results indicate that different mineral distributions significantly impact the macroscopic mechanical behaviors,but variability in numerical simulation results decreases with increasing specimen size.The compressive and tensile strength values of the reconstructed numerical models show less variation than those of natural granite specimens.This suggests that,beyond mineral distribution,other factors such as internal defects within natural granite contribute to the observed discrepancies.Additionally,the bubbling method shows great potential for modeling porous structures and offers high computational efficiency.展开更多
This study systematically analyzes the influence of different combined joint dip angles on rock mass failure modes and damage mechanisms through uniaxial compression tests on granite specimens with prefabricated Y-sha...This study systematically analyzes the influence of different combined joint dip angles on rock mass failure modes and damage mechanisms through uniaxial compression tests on granite specimens with prefabricated Y-shaped discontinuities,combined with digital speckle and acoustic emission(AE)monitoring.The results show that as the dip angle of the primary joint increases,the failure mode transitions from overall failure to wedge block ejection and shear failure.A failure mode identification model was established based on main crack dip angle thresholds(40°,45°),uniaxial compressive strength thresholds(40,90 MPa),and energy core zone proportion thresholds(20%,10%),achieving an accuracy of 93.3%.In the overall failure and wedge block ejection modes,a sharp increase in shear crack ratio and a sudden drop in the acoustic emission b-value occur in the high-stress phase(>0.6σ_(c)),while in the shear failure mode,significant fluctuations are observed due to the shear-tension alternation,making it difficult to identify a single critical point.Additionally,joint slip in the overall failure and wedge block ejection modes primarily occurs during the failure instability phase(>0.8σ_(c)).These findings provide theoretical support for stability evaluation of complex fractured rock masses and practical guidance for engineering safety construction.展开更多
To further study the load transfer mechanism of roofemulti-pillarefloor system during cascading pillar failure(CPF),numerical simulation and theoretical analysis were carried out to study the three CPF modes according...To further study the load transfer mechanism of roofemulti-pillarefloor system during cascading pillar failure(CPF),numerical simulation and theoretical analysis were carried out to study the three CPF modes according to the previous experimental study on treble-pillar specimens,e.g.successive failure mode(SFM),domino failure mode(DFM)and compound failure mode(CFM).Based on the finite element code rock failure process analysis(RFPA^(2D)),numerical models of treble-pillar specimen with different mechanical properties were established to reproduce and verify the experimental results of the three CPF modes.Numerical results show that the elastic rebound of roofefloor system induced by pillar instability causes dynamic disturbance to adjacent pillars,resulting in sudden load increases and sudden jump displacement of adjacent pillars.The phenomena of load transfer in the roofemulti-pillarefloor system,as well as the induced accelerated damage behavior in adjacent pillars,were discovered and studied.In addition,based on the catastrophe theory and the proposed mechanical model of treble-pillar specimen edisc spring group system,a potential function that characterizes the evolution characteristics of roof emulti-pillarefloor system was established.The analytical expressions of sudden jump and energy release of treble-pillar specimenedisc spring group system of the three CPF modes were derived according to the potential function.The numerical and theoretical results show good agreement with the experimental results.This study further reveals the physical essence of load transfer during CPF of roof emulti-pillarefloor system,which provides references for mine design,construction and disaster prevention.展开更多
基金funded by the National Key R&D Program of China(Grant No.2022YFC2903904)the National Natural Science Foundation of China(Grant Nos.51904057 and U1906208).
文摘Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this challenge,nonlinear stress boundaries for a numerical model are determined through regression analysis of a series of nonlinear coefficient matrices,which are derived from the bubbling method.Considering the randomness and flexibility of the bubbling method,a parametric study is conducted to determine recommended ranges for these parameters,including the standard deviation(σb)of bubble radii,the non-uniform coefficient matrix number(λ)for nonlinear stress boundaries,and the number(m)and positions of in situ stress measurement points.A model case study provides a reference for the selection of these parameters.Additionally,when the nonlinear in situ stress inversion method is employed,stress distortion inevitably occurs near model boundaries,aligning with the Saint Venant's principle.Two strategies are proposed accordingly:employing a systematic reduction of nonlinear coefficients to achieve high inversion accuracy while minimizing significant stress distortion,and excluding regions with severe stress distortion near the model edges while utilizing the central part of the model for subsequent simulations.These two strategies have been successfully implemented in the nonlinear in situ stress inversion of the Xincheng Gold Mine and have achieved higher inversion accuracy than the linear method.Specifically,the linear and nonlinear inversion methods yield root mean square errors(RMSE)of 4.15 and 3.2,and inversion relative errors(δAve)of 22.08%and 17.55%,respectively.Therefore,the nonlinear inversion method outperforms the traditional multiple linear regression method,even in the presence of a systematic reduction in the nonlinear stress boundaries.
基金funded by the National Key Research and Development Program of China(Grant No.2022YFC2903904)National Natural Science Foundation of China(Grant Nos.U1906208 and U21A20106).
文摘Accurately reconstructing rock structures using numerical methods is vital in rock mechanics research community,especially when obtaining rock samples is difficult and expensive.The reconstructed models must reflect the comprehensive characteristics of natural rock,including mineral content and spatial distributions.This study employs the bubbling method to reconstruct granite containing multiple minerals in both two-(2D)and three-dimensions(3D),proposing a general procedure for granite structure reconstruction.The bubbling method utilizes numerous bubbles(hemispheres or spheres)of varying sizes and gradually changing properties,which are randomly overlapped to create a heterogeneous plane(2D)or space(3D).The properties of these overlapped areas are adjusted based on the sum of neighboring bubbles'properties,allowing specific regions with extreme properties to be selected and intercepted to form the desired mineral shapes.The results demonstrate that the reproduced granite samples can accurately exhibit the mineral distributions and sizes of real granite,quantified by fractal dimension(D)and the hourglass parameter(V_(Sum)=V_(Total)).The proposed method is also suitable for reconstructing anisotropic granite models,with anisotropy described by a fitted elliptic curve derived from ratios between directional mineral sizes and cross-sectional dimensions.Based on these findings,a series of numerical granite models with similar structures were reconstructed and tested.Results indicate that different mineral distributions significantly impact the macroscopic mechanical behaviors,but variability in numerical simulation results decreases with increasing specimen size.The compressive and tensile strength values of the reconstructed numerical models show less variation than those of natural granite specimens.This suggests that,beyond mineral distribution,other factors such as internal defects within natural granite contribute to the observed discrepancies.Additionally,the bubbling method shows great potential for modeling porous structures and offers high computational efficiency.
基金supported by the National Key Research and Development Program of China(No.2022YFC2903903)the National Natural Science Foundation of China(No.52374157)+1 种基金the General Project of National Natural Science Foundation of China(No.52374157)Ordos Major Science and Technology Program(No.JBGS-2023-003)。
文摘This study systematically analyzes the influence of different combined joint dip angles on rock mass failure modes and damage mechanisms through uniaxial compression tests on granite specimens with prefabricated Y-shaped discontinuities,combined with digital speckle and acoustic emission(AE)monitoring.The results show that as the dip angle of the primary joint increases,the failure mode transitions from overall failure to wedge block ejection and shear failure.A failure mode identification model was established based on main crack dip angle thresholds(40°,45°),uniaxial compressive strength thresholds(40,90 MPa),and energy core zone proportion thresholds(20%,10%),achieving an accuracy of 93.3%.In the overall failure and wedge block ejection modes,a sharp increase in shear crack ratio and a sudden drop in the acoustic emission b-value occur in the high-stress phase(>0.6σ_(c)),while in the shear failure mode,significant fluctuations are observed due to the shear-tension alternation,making it difficult to identify a single critical point.Additionally,joint slip in the overall failure and wedge block ejection modes primarily occurs during the failure instability phase(>0.8σ_(c)).These findings provide theoretical support for stability evaluation of complex fractured rock masses and practical guidance for engineering safety construction.
基金financially supported by the National Key R&D Program of China(Grant No.2022YFC2903901)Enlisting and Leading Project of the Key Scientific and Technological Innovation in Heilongjiang Province,China(Grant No.2021ZXJ02A03,04)the North China University of Water Resources and Electric Power Launch Fund for High-level Talents Research(Grant No.40937).
文摘To further study the load transfer mechanism of roofemulti-pillarefloor system during cascading pillar failure(CPF),numerical simulation and theoretical analysis were carried out to study the three CPF modes according to the previous experimental study on treble-pillar specimens,e.g.successive failure mode(SFM),domino failure mode(DFM)and compound failure mode(CFM).Based on the finite element code rock failure process analysis(RFPA^(2D)),numerical models of treble-pillar specimen with different mechanical properties were established to reproduce and verify the experimental results of the three CPF modes.Numerical results show that the elastic rebound of roofefloor system induced by pillar instability causes dynamic disturbance to adjacent pillars,resulting in sudden load increases and sudden jump displacement of adjacent pillars.The phenomena of load transfer in the roofemulti-pillarefloor system,as well as the induced accelerated damage behavior in adjacent pillars,were discovered and studied.In addition,based on the catastrophe theory and the proposed mechanical model of treble-pillar specimen edisc spring group system,a potential function that characterizes the evolution characteristics of roof emulti-pillarefloor system was established.The analytical expressions of sudden jump and energy release of treble-pillar specimenedisc spring group system of the three CPF modes were derived according to the potential function.The numerical and theoretical results show good agreement with the experimental results.This study further reveals the physical essence of load transfer during CPF of roof emulti-pillarefloor system,which provides references for mine design,construction and disaster prevention.
