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Optimizing profile line interval for enhanced accuracy in rock joint morphology and shear strength assessments

International Journal of Mining Science and Technology 2024年第5期34卷 587-608页

作者： Leibo Song Quan Jiang Shigui Du Jiamin Song Gang Wang Yanting Gu Xingkai Wang Jinzhong Wu School of Civil Engineering Shaoxing UniversityShaoxing 312000China Key Laboratory of rock mechanics and geohazards of Zhejiang Province Shaoxing UniversityShaoxing 312000China State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China Institute of rock mechanics Ningbo UniversityNingbo 315211China

2D profile lines play a critical role in cost-effectively evaluating rock joint properties and shear ***, the interval(ΔI_(L)) between these lines significantly impacts roughness and shear strength assessments. A detailed study of 45 joint samples using four statistical measures across 500 different ΔI_(L)values identified a clear line interval effect with two stages: stable and *** statistical analysis showed a linear relationship between the error bounds of four parameters,shear strength evaluation, and their corresponding maximum ΔI_(L)values, where the gradient k of this linear relationship was influenced by the basic friction angle and normal stress. Accounting for these factors,lower-limit linear models were employed to determine the optimal ΔI_(L)values that met error tolerances(1%–10%) for all metrics and shear strength. The study also explored the consistent size effect on joints regardless of ΔI_(L)changes, revealing three types of size effects based on morphological ***, larger joints required generally higher ΔI_(L)to maintain the predefined error limits, suggesting an increased interval for large joint analyses. Consequently, this research provides a basis for determining the optimal ΔI_(L), improving accuracy in 2D profile line assessments of joint characteristics.

关键词： rock joint Roughness Shear strength Size effect Profile line interval effect

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Insight into the Permeability and Microstructure Evolution Mechanism of the Sliding Zone Soil: A Case Study from the Huangtupo Landslide, Three Gorges Reservoir, China

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Journal of Earth Science 2024年第3期35卷 941-954页

作者： Qianyun Wang Huiming Tang Pengju An Kun Fang Junrong Zhang Minghao Miao Qingwen Tan Lei Huang Shengming Hu Badong National Observation and Research Station of geohazards China University of GeosciencesWuhan 430074China Faculty of Engineering China University of GeosciencesWuhan 430074China Institute of rock mechanics Ningbo UniversityNingbo 315211China National and Provincial Joint Engineering Laboratory for the Hydraulic Engineering Safety and Efficient Utilization of Water Resources of Poyang Lake Basin Nanchang Institute of TechnologyNanchang 330099China

A large number of laboratory investigations related to the permeability have been conducted on the sliding *** little attention has been paid to the particular sliding zones of the slideprone Badong ***,we experimentally investigate the permeability nature and the mechanism of seepage in the viscous sliding zone of the Huangtupo *** seepage tests have been performed first with consideration of six dry densities and thirteen hydraulic gradients,in conjunction with the mercury intrusion porosimetry test and scanning electron microscopy test for the microstructure analysis after *** results show that seepage in the sliding zone soil does not follow Darcy’s Law,since there is a threshold hydraulic gradient(i0)below which no flow is observed and a critical hydraulic gradient(icr)over which the hydraulic conductivity(K)tends to be *** percentage of bound water could be responsible for the occurrence of i0 and ***,pore size distributions(PSD)less than 0.6µm and between 10 and 90µm exhibit positive and negative correlations with the i0,respectively,indicating that the i0 is related to the *** mechanism accounting for this result is that pore water pressure forces fine clay particles into the surrounding large pores and converts arranged particles to discretely distributed ones,thereby weakening the connectivity of *** seepages in the sliding zones behave differently from that in the sliding mass and sliding bed in response to the permeability.

关键词： reservoir landslides sliding zone soil permeability microstructure seepage.

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Three-dimensional stress variation characteristics in deep hard rock of CJPL-Ⅱ project based on in-situ monitoring

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International Journal of Mining Science and Technology 2024年第2期34卷 179-195页

作者： Minzong Zheng Shaojun Li Zejie Feng Huaisheng Xu Yaxun Xiao State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China University of Chinese Academy of Sciences Beijing 100049China

In deep hard rock excavation, stress plays a pivotal role in inducing stress-controlled failure. While the impact of excavation-induced stress disturbance on rock failure and tunnel stability has undergone comprehensive examination through laboratory tests and numerical simulations, its validation through insitu stress tests remains unexplored. This study analyzes the three-dimensional stress changes in the surrounding rock at various depths, monitored during the excavation of B2 Lab in China Jinping Underground Laboratory Phase Ⅱ(CJPL-Ⅱ). The investigation delves into the three-dimensional stress variation characteristics in deep hard rock, encompassing stress components and principal stress. The results indicate changes in both the magnitude and direction of the principal stress during tunnel excavation. To quantitatively describe the degree of stress disturbance, a series of stress evaluation indexes are established based on the distances between stress tensors, including the stress disturbance index(SDI), the principal stress magnitude disturbance index(SDIm), and the principal stress direction disturbance index(SDId). The SDI indicates the greatest stress disturbance in the surrounding rock is 4.5 m from the tunnel wall in B2 Lab. SDIm shows that the principal stress magnitude disturbance peaks at2.5 m from the tunnel wall. SDId reveals that the largest change in principal stress direction does not necessarily occur near the tunnel wall but at a specific depth from it. The established relationship between SDI and the depth of the excavation damaged zone(EDZ) can serve as a criterion for determining the depth of the EDZ in deep hard rock engineering. Additionally, it provides a reference for future construction and support considerations.

关键词： Disturbance stress Tensor distance Stress disturbance index Principal stress direction Underground research laboratory

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Swelling behaviors of heterogeneous red-bed mudstone subjected to different vertical stresses

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Journal of rock mechanics and Geotechnical Engineering 2024年第5期16卷 1847-1863页

作者： Kang Huang Zhangjun Dai Chengzeng Yan Fei Yu Wei Zhang Shanxiong Chen State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of Sciences Beijing100049China Faculty of Engineering China University of GeosciencesWuhanChina International Joint Research center for Deep Earth Drilling and Resource Development China University of GeosciencesWuhan430074China

In this study,the axial swelling strain of red-bed mudstone under different vertical stresses are measured by swell-under-load method,and the microstructure of mudstone after hygroscopic swelling is studied by mercury intrusion porosimetry(MIP).The weakening coefficient and Weibull distribution function are introduced into the coupling model of mudstone moisture diffusion-swelling deformation-fracture based on finite-discrete element method(FDEM).The weakening effect of moisture on mudstone's mechanical parameters,as well as the heterogeneity of swelling deformation and stress distribution,is *** microcrack behavior and energy evolution of mudstone during hygroscopic swelling deformation under different vertical stresses are *** results show that the axial swelling strain of mudstone decreases with increase of the vertical *** low vertical stresses,moisture absorption in mudstone leads to formation of cracks caused by hydration-induced *** high vertical stresses,a muddy sealing zone forms on the mudstone surface,preventing further water *** simulation results of mudstone swelling deformation also demonstrate that it involves both swelling of the mudstone matrix and swelling caused by crack ***,crack expansion plays a dominant role in mudstone *** increasing vertical stress,the cracks in mudstone change from tensile cracks to shear cracks,resulting in a significant reduction in the total number of *** the evolution of mudstone kinetic energy shows similarities under different vertical stresses,the evolution of strain energy varies significantly due to the presence of different types of cracks in the *** findings provide a theoretical basis for understanding the hygroscopic swelling deformation mechanism of red-bed mudstone at various depths.

关键词： Heterogeneous red-bed mudstone Self-sealing band Matric swelling and crack expansion FDEM Microcracks Energy evolution

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Reliability Analysis of Reinforcement Based on GM(1,1)-Markov Semi-immersion Test

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Journal of Wuhan University of Technology(Materials Science) 2024年第5期39卷 1177-1187页

作者： FU Yong QIAO Hongxia HAKUZWEYEZU Theogene School of Civil Engineering Lanzhou University of TechnologyLanzhou 730050China Gansu Advanced Civil Engineering Materials Engineering Research center Lanzhou 730050China State Key Laboratory of Geomechanics and Geotechnical Enginering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China Civil Engineering Department University of Chinese Academy of SciencesBeijing 100049China

To investigate the corrosion degradation law and service life of reinforced concrete in various salt solution environments,reinforced concrete specimens were semi-immersed in 3%Na_(2)CO_(3)(N3-0-0),3%Na_(2)CO_(3)+3%NaCl(N3-Cl3-0)and 3%Na_(2)CO_(3)+3%NaCl+3%Na_(2)SO_(4)(N3-Cl3-S3)salt *** electrochemical workstation was used for regular non-destructive testing,and the polarization curve and related electrochemical parameters were used as the macroscopic durability evaluation indicators,while microscopic analysis of steel bar corrosion products was performed in combination with SEM and *** addition,the corrosion current density degradation model of GM(1,1)was established and compared with the modified GM(1,1)-Markov degradation *** results showed that the prediction error of the GM(1,1)-Markov model was smaller and more accurate than that of GM(1,1).The reinforced concrete specimens in the N3-0-0,N3-Cl3-0 and N3-Cl3-S3 solutions reached the failure state in 3.08,1.67,and 2.30 years,respectively,as predicted by the GM(1,1)-Markov *** to ESM and EDS microscopic analysis of reinforcement,carbonate had no significant effect on reinforcement corrosion,chloride ions played a dominant role in reinforcement corrosion,and sulfate ion improved concrete's resistance to chloride ion *** on GM(1,1)-Markov model,the failure and damage of reinforced concrete in saline soil areas can be quantitatively evaluated in the whole life cycle,which provides a theoretical basis for the early maintenance or reinforcing of reinforced concrete.

关键词： salt solution semi-immersion corrosion current density GM(1,1)-Markov

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Shear behavior and off-fault damage of saw-cut smooth and tension-induced rough joints in granite

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Journal of rock mechanics and Geotechnical Engineering 2024年第4期16卷 1216-1230页

作者： Fanzhen Meng Feili Wang Louis Ngai Yuen Wong Jie Song Muzi Li Chuanqing Zhang Liming Zhang College of Science Qingdao University of TechnologyQingdao266033China Department of Earth Sciences The University of Hong KongPokfulamHong KongChina State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China Cooperative Innovation center of Engineering Construction and Safety Shandong Peninsula Blue Economic Zone Qingdao266033China

The damage of rock joints or fractures upon shear includes the surface damage occurring at the contact asperities and the damage beneath the shear surface within the host *** latter is commonly known as off-fault damage and has been much less investigated than the surface *** main contribution of this study is to compare the results of direct shear tests conducted on saw-cut planar joints and tension-induced rough granite joints under normal stresses ranging from 1 MPa to 50 *** shear-induced off-fault damages are quantified and compared with the optical microscope *** results clearly show that the planar joints slip stably under all the normal stresses except under 50 MPa,where some local fractures and regular stick-slip occur towards the end of the *** post-peak stress drop and stick-slip occur for all the rough *** residual shear strength envelopes for the rough joints and the peak shear strength envelope for the planar joints almost *** root mean square(RMS)of asperity height for the rough joints decreases while it increases for the planar joint after shear,and a larger normal stress usually leads to a more significant decrease or increase in ***,the extent of off-fault damage(or damage zone)increases with normal stress for both planar and rough joints,and it is restricted to a very thin layer with limited micro-cracks beneath the planar joint *** comparison,the thickness of the damage zone for the rough joints is about an order of magnitude larger than that of the planar joints,and the coalesced micro-cracks are generally inclined to the shear direction with acute *** findings obtained in this study contribute to a better understanding on the frictional behavior and damage characteristics of rock joints or fractures with different roughness.

关键词： Planar joint Rough joint Shear behavior Off-fault damage Micro-cracks

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A modified back analysis method for deep excavation with multi-objective optimization procedure

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Journal of rock mechanics and Geotechnical Engineering 2024年第4期16卷 1373-1387页

作者： Chenyang Zhao Le Chen Pengpeng Ni Wenjun Xia Bin Wang State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China Guangdong Research center for Underground Space Exploitation Technology School of Civil EngineeringSun Yat-sen UniversityGuangzhou510275China Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) Zhuhai519000China Jiangsu Provincial Transportation Engineering Construction Bureau Nanjing210004China

Real-time prediction of excavation-induced displacement of retaining pile during the deep excavation process is crucial for construction *** paper proposes a modified back analysis method with multi-objective optimization procedure,which enables a real-time prediction of horizontal displacement of retaining pile during *** opposed to the traditional stage-by-stage back analysis,time series monitoring data till the current excavation stage are utilized to form a multi-objective ***,the multi-objective particle swarm optimization (MOPSO) algorithm is applied for parameter *** optimized model parameters are immediately adopted to predict the excavation-induced pile deformation in the continuous construction *** achieve efficient parameter optimization and real-time prediction of system behavior,the back propagation neural network (BPNN) is established to substitute the finite element model,which is further implemented together with MOPSO for automatic *** proposed approach is applied in the Taihu tunnel excavation project,where the effectiveness of the method is demonstrated via the comparisons with the site monitoring *** method is reliable with a prediction accuracy of more than 90%.Moreover,different optimization algorithms,including non-dominated sorting genetic algorithm (NSGA-II),Pareto Envelope-based Selection Algorithm II (PESA-II) and MOPSO,are compared,and their influences on the prediction accuracy at different excavation stages are *** results show that MOPSO has the best performance for high dimensional optimization task.

关键词： Multi-objective optimization Back analysis Surrogate model Multi-objective particle swarm optimization(MOPSO) Deep excavation

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Unraveling engineering disturbance effects on deformation in red-bed mudstone railway cuttings:incorporating crack-facilitated moisture diffusion

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Journal of Mountain Science 2024年第5期21卷 1663-1682页

作者： HUANG Kang DAI Zhangjun YAN Chengzeng YAO Junkai CHI Zecheng CHEN Shanxiong State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China University of Chinese Academy of Sciences Beijing 100049China Faculty of Engineering China University of GeosciencesWuhan 430074China International Joint Research center for Deep Earth Drilling and Resource Development China University of GeosciencesWuhan 430074China China Academy of Railway Sciences Corporation Limited Beijing 100081China

Red-bed mudstone, prevalent in southwest China, poses a formidable challenge due to its hydrophilic clay minerals, resulting in expansion, deformation, and cracking upon exposure to moisture. This study addresses uplift deformation disasters in high-speed railways by employing a moisture diffusion-deformation-fracture coupling model based on the finite-discrete element method(FDEM). The model integrates the influence of cracks on moisture diffusion. The investigation into various excavation depths reveals a direct correlation between depth and the formation of tensile cracks at the bottom of the railway cutting. These cracks expedite moisture migration, significantly impacting the temporal and spatial evolution of the moisture field. Additionally, crack expansion dominates hygroscopic deformation, with the lateral coordinate of the crack zone determining peak vertical displacement. Furthermore, key factors influencing deformation in railway cuttings, including the swelling factor and initial moisture content at the bottom of the cutting, are explored. The number of tensile and shear cracks increases with greater excavation depth, particularly concerning shear cracks. Higher swelling factors and initial moisture contents result in an increased total number of cracks, predominantly shear cracks. Numerical calculations provide valuable insights, offering a scientific foundation and directional guidance for the precise prevention, control, prediction, and comprehensive treatment of mudstone-related issues in high-speed railways.

关键词： Red-bed mudstone Railway cutting FDEM Moisture diffusion Deformation Crack

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Numerical and theoretical study of load transfer behavior during cascading pillar failure

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Journal of rock mechanics and Geotechnical Engineering 2024年第8期16卷 3014-3033页

作者： Hangyu Dong Wancheng Zhu Leilei Niu Chen Hou Xige Liu College of Geosciences and Engineering North China University of Water Resources and Electric PowerZhengzhou450046China center for rock Instability and Seismicity Research School of Resource and Civil EngineeringNortheastern UniversityShenyang110819China

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,*** 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 *** 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 *** phenomena of load transfer in the roofemulti-pillarefloor system,as well as the induced accelerated damage behavior in adjacent pillars,were discovered and *** 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 *** 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 *** numerical and theoretical results show good agreement with the experimental *** 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.

关键词： Cascading pillar failure(CPF) Load transfer Multi-pillar Numerical simulation

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Limit state analysis of rigid retaining structures against seismically induced passive failure in heterogeneous soils

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Journal of rock mechanics and Geotechnical Engineering 2024年第3期16卷 1095-1105页

作者： Jianfeng Zhou Changbing Qin College of Civil Engineering Huaqiao UniversityXiamen362021China School of Civil Engineering Chongqing UniversityChongqing400045China Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityChongqing400045China National Joint Engineering Research center of geohazards Prevention in the Reservoir Areas Chongqing UniversityChongqing400045China

Soils are not necessarily uniform and may present linearly varied or layered characteristics,for example the backfilled soils behind rigid retaining *** the presence of large lateral thrust imposed by arch bridge,passive soil failure is possible.A reliable prediction of passive earth pressure for the design of such wall is challenging in complicated soil strata,when adopting the conventional limit analysis *** order to overcome the challenge for generating a kinematically admissible velocity field and a statically allowable stress field,finite element method is incorporated into limit analysis,forming finiteelement upper-bound(FEUB)and finite-element lower-bound(FELB)***-static,original and modified pseudo-dynamic approaches are adopted to represent seismic acceleration *** generating feasible velocity and stress fields within discretized elements based on specific criteria,FEUB and FELB formulations of seismic passive earth pressure(coefficient K_(P))can be derived from work rate balance equation and stress *** to an interior point algorithm,optimal upper and lower bound solutions are *** proposed FEUB and FELB procedures are well validated by limit equilibrium as well as lower-bound and kinematic *** studies are carried out to investigate the effects of influential factors on seismic K_(P).Notably,true solution of K_(P) is well estimated based on less than 5%difference between FEUB and FELB solutions under such complex scenarios.

关键词： Retaining wall Passive earth pressure Earthquakes Finite-element limit-analysis methods

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