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Effects of thawing-induced softening on fracture behaviors of frozen rock

Journal of Rock Mechanics and Geotechnical Engineering 2024年第3期16卷 979-989页

作者： Ting Wang Hailiang Jia Qiang Sun Xianjun Tan Liyun Tang College of Geology and Environment Xi’an University of Science and TechnologyXi’an710054China College of Architecture and Civil Engineering Xi’an University of Science and TechnologyXi’an710054China State Key Laboratory of geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430064China

Due to the presence of ice and unfrozen water in pores of frozen rock,the rock fracture behaviors are susceptible to *** this study,the potential thawing-induced softening effects on the fracture behaviors of frozen rock is evaluated by testing the tension fracture toughness(KIC)of frozen rock at different temperatures(i.e.-2.℃,-15℃,-12.,-10℃,-8℃,-6℃,-4℃,-2.,and 0℃).Acoustic emission(AE)and digital image correlation(DIC)methods are utilized to analyze the microcrack propagation during *** melting of pore ice is measured using nuclear magnetic resonance(NMR)*** results indicate that:(1)The KIC of frozen rock decreases moderately between-2.℃ and-4℃,and rapidly between-4℃ and 0℃.(2.At-2.℃ to-4℃,the fracturing process,deduced from the DIC results at the notch tip,exhibits three stages:elastic deformation,microcrack propagation and microcrack ***,at-4℃e0℃,only the latter two stages are observed.(3)At-4℃e0℃,the AE activities during fracturing are less than that at-2.℃ to-4℃,while more small events are reported.(4)The NMR results demonstrate a reverse variation trend in pore ice content with increasing temperature,that is,a moderate decrease is followed by a sharp decrease and-4℃ is exactly the critical ***,we interpret the thawing-induced softening effect by linking the evolution in microscopic structure of frozen rock with its macroscopic fracture behaviors as follow:from-2.℃ to-4℃,the thickening of the unfrozen water film diminishes the cementation strength between ice and rock skeleton,leading to the decrease in fracture ***-4℃ to 0℃,the cementation effect of ice almost vanishes,and the filling effect of pore ice is reduced significantly,which facilitates microcrack propagation and thus the easier fracture of frozen rocks.

关键词： Frozen sandstone Different thawing temperature Fracture toughness Microcrack propagation process Unfrozen water content

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Clogging caused by coupled grain migration and compaction effect during groundwater recharge for unconsolidated sandstone reservoir in groundwater-source heat pump

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第8期16卷 2947-2959页

作者： Fujian Yang Jing Luo Guiling Wang Hejuan Liu Dawei Hu Hui Zhou State Key Laboratory of geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of Sciences Beijing100049China Sinopec Star Hubei New Energy Development Co. Ltd.Wuhan430010China institute of Hydrogeology and Environmental Geology Chinese Academy of Geological SciencesShijiazhuang050061China

In unconsolidated sandstone reservoirs,presence of numerous movable grains and a complex grain size composition necessitates a clear understanding of the physical clogging process for effective groundwater recharge in groundwater-source heat pump *** investigate this,a series of seepage experiments was conducted under in situ stress conditions using unconsolidated sandstone samples with varying grain *** clogging phenomenon arises from the combined effects of grain migration and compaction,wherein the migration of both original and secondary crushed fine-grain particles blocks the seepage ***,grain composition influences the migration and transport properties of the *** samples composed of smaller grains,the apparent permeability demonstrates a transition from stability to *** contrast,samples with larger grains experience a skip at the stability stage and directly enter the decrease stage,with a minor exception of a slight increase ***,a unique failure mode characterized by diameter shrinkage in the upper part of the sample is observed due to the combined effects of grain migration and in situ stress-induced *** testing results contribute to a better understanding of the clogging mechanism caused by the coupled effects of grain migration and compaction during groundwater recharge in unconsolidated sandstone reservoirs used in groundwater-source heat pump systems.

关键词： Groundwater-source heat pump Clogging Grain migration Compaction effect Groundwater recharge Unconsolidated sandstone

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Shear mechanical properties and fracturing responses of layered rough jointed rock-like materials

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International Journal of Minerals,Metallurgy and Materials 2024年第11期31卷 2417-2434页

作者： Xinxin Nie Qian Yin Manchao He Qi Wang Hongwen Jing Bowen Zheng Bo Meng Tianci Deng Zheng Jiang Jiangyu Wu State Key Laboratory for geomechanics&Deep Underground Engineering China University of Mining and TechnologyXuzhou 221116China State Key Laboratory for geomechanics&Deep Underground Engineering China University of Mining and Technology(Beijing)Beijing 100083China Key Laboratory of Shale Gas and Geoengineering Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Department of Materials University of OxfordOxford OX13PHUK

This study aims to investigate mechanical properties and failure mechanisms of layered rock with rough joint surfaces under direct shear *** layered samples with dimensions of 100 mm×100 mm×100 mm were casted using rock-like materials,with anisotropic angle(α)and joint roughness coefficient(JRC)ranging from 15°to 75°and 2.2.,*** direct shear tests were conducted under the application of initial normal stress(σ_(n)) ranging from 1-4 *** test results indicate significant differences in mechanical properties,acoustic emission(AE)responses,maximum principal strain fields,and ultimate failure modes of layered samples under different test *** peak stress increases with the increasingαand achieves a maximum value atα=60°or 75°.As σ_(n) increases,the peak stress shows an increasing trend,with correlation coefficients R² ranging from 0.918 to 0.995 for the linear least squares *** JRC increases from 2.4 to 18-2.,the cohesion increases by 86.32.whenα=15°,while the cohesion decreases by 2..93%whenα=75°.The differences in roughness characteristics of shear failure surface induced byαresult in anisotropic post-peak AE responses,which is characterized by active AE signals whenαis small and quiet AE signals for a largeα.For a given JRC=6-8 andσ_(n)=1 MPa,asαincreases,the accumulative AE counts increase by 2.4.31%(αincreased from 15°to 60°),and then decrease by 14.68%(αincreased from 60°to 75°).The shear failure surface is formed along the weak interlayer whenα=15°and penetrates the layered matrix whenα=60°.Whenα=15°,as σ_(n) increases,the adjacent weak interlayer induces a change in the direction of tensile cracks propagation,resulting in a stepped pattern of cracks *** increase in JRC intensifies roughness characteristics of shear failure surface for a smallα,however,it is not pronounced for a largeα.The findings will contribute to a better understanding of the mechanical responses and failure mechanisms of the layered roc

关键词： layered samples anisotropic angle joint roughness coefficient mechanical properties acoustic emission response fracturing evolution failure modes

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Analysis of acoustic propagation models and dissipation mechanisms of saturated sandy sediments based on the Biot theory

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Chinese Journal of Acoustics 2024年第3期43卷 363-379页

作者： ZHANG Yong MIAO Jinqiang WANG Yong LIU Guanshi College of Civil Engineering Zhejiang University of TechnologyHangzhou310023 State Key Laboratory of geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071

To investigate the dispersion characteristics of shallow sandy sediments on the seabed,a comparative analysis was conducted on the longitudinal and transverse wave dispersion features in typical sandy sediments described by the three acoustic propagation models using the Biot model,the Biot-Stoll model and the Biot-Stoll with contact squirt flow and shear drag(BICSQS)model developed from the theory of porous *** effects of different dissipation mechanisms in the models on the acoustic dispersion relationship were ***,the applicability of the models to sandy sediments was explored using integrating empirical *** results indicate that the acoustic dispersion characteristics of sediments are the result of different dissipation mechanisms,which are different in different frequency bands and have different effects on the propagation of longitudinal and transverse waves in the same frequency *** the frequency increases,the measured acoustic speed and attenuation of sandy sediments exhibit higher dispersion trends than those predicted by the Biot and Biot-Stoll *** contrast,the BICSQS model demonstrates a more reasonable prediction and interpretation of experimental phenomena with better applicability.

关键词： sandy shallow dispersion

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Consolidation of high replacement ratio stone column-reinforced ground:Analytical solutions incorporating clogging effect

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第8期16卷 3311-3326页

作者： Jinxin Sun Mengmeng Lu Baolong Xu Jie Shan School of Mechanics and Civil Engineering China University of Mining and TechnologyXuzhou221116China Key Laboratory for geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou221006China

The utilization of stone columns has emerged as a popular ground improvement strategy,whereas the drainage performance can be adversely hampered by clogging *** the ample progress of calculation methods for the consolidation of stone column-improved ground,theoretical investigations into the clogging effect have not been thoroughly ***,it is imperative to involve the column consolidation deformation to mitigate computational error on the consolidation of composite ground with high replacement *** this context,an analytical model accounting for the initial clogging and coupled time and depth-dependent clogging of stone columns is ***,the resulting governing equations and analytical solutions are obtained under a new flow continuity relationship to incorporate column consolidation *** accuracy and reliability of the proposed model are illustrated by degradation analysis and case studies with good ***,the computed results of the current study are juxtaposed against the existing models,and an in-depth assessment of the impacts of several crucial parameters on the consolidation behavior is *** results reveal that ignoring column consolidation deformation leads to an overestimate of the consolidation rate,with maximum error reaching up to 16%as the replacement ratio ***,the initial clogging also has a significant influence on the consolidation ***,the increment of depth and time-clogging factors a and b will induce a noticeable retardation of the consolidation process,particularly in the later stage.

关键词： Consolidation Composite ground Stone column Clogging effect Ground improvement Analytical model

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Characterization and spatial analysis of coseismic landslides triggered by the Luding Ms 6.8 earthquake in the Xianshuihe fault zone, Southwest China

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Journal of Mountain Science 2024年第1期21卷 160-181页

作者： GUO Changbao LI Caihong YANG Zhihua NI Jiawei ZHONG Ning WANG Meng YAN Yiqiu SONG Deguang ZHANG Yanan ZHANG Xianbing WU Ruian CAO Shichao SHAO Weiwei institute of geomechanics Chinese Academy of Geological SciencesBeijing 100081China Key Laboratory of Active Tectonics and Geological Safety Ministry of Natural ResourcesBeijing 100081China Research Center of Neotectonism and Crustal Stability China Geological SurveyBeijing 100081China School of Earth Sciences and Resources China University of GeosciencesBeijing 100083China Sichuan institute of Geological Survey Chengdu 610081China

On September 5, 2.2., a magnitude Ms 6.8 earthquake occurred along the Moxi fault in the southern part of the Xianshuihe fault zone located in the southeastern margin of the Tibetan Plateau,resulting in severe damage and substantial economic loss. In this study, we established a coseismic landslide database triggered by Luding Ms 6.8 earthquake, which includes 4794 landslides with a total area of 46.79 km^(2.. The coseismic landslides primarily consisted of medium and small-sized landslides, characterized by shallow surface sliding. Some exhibited characteristics of high-position initiation resulted in the obstruction or partial obstruction of rivers, leading to the formation of dammed lakes. Our research found that the coseismic landslides were predominantly observed on slopes ranging from 30° to 50°, occurring at between 1000 m and 2.00 m, with slope aspects varying from 90° to 180°. Landslides were also highly developed in granitic bodies that had experienced structural fracturing and strong-tomoderate weathering. Coseismic landslides concentrated within a 6 km range on both sides of the Xianshuihe and Daduhe fault zones. The area and number of coseismic landslides exhibited a negative correlation with the distance to fault lines, road networks, and river systems, as they were influenced by fault activity, road excavation, and river erosion. The coseismic landslides were mainly distributed in the southeastern region of the epicenter, exhibiting relatively concentrated patterns within the IX-degree zones such as Moxi Town, Wandong River basin, Detuo Town to Wanggangping Township. Our research findings provide important data on the coseismic landslides triggered by the Luding Ms 6.8 earthquake and reveal the spatial distribution patterns of these landslides. These findings can serve as important references for risk mitigation, reconstruction planning, and regional earthquake disaster research in the earthquake-affected area.

关键词： Luding earthquake Coseismic landslides Remote sensing interpretation Spatial distribution Xianshuihe fault Earthquake fault

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Experimental study on the effect of unloading rate on gneiss rockburst

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第6期16卷 2064-2076页

作者： Dongqiao Liu Jie Sun Ran Li Manchao He Binghao Cao Chongyuan Zhang Wen Meng State Key Laboratory for Tunnel Engineering China University of Mining and TechnologyBeijing100083China Key Laboratory of Active Tectonics and Geological Safety Ministry of Natural ResourcesInstitute of GeomechanicsChinese Academy of Geological SciencesBeijing100081China School of Mechanics and Civil Engineering China University of Mining and TechnologyBeijing100083China

Rockburst are often encountered in tunnel construction due to the complex geological *** study the influence of unloading rate on rockburst,gneiss rockburst experiments were conducted under three groups of unloading rates.A high-speed photography system and acoustic emission(AE)system were used to monitor the entire process of rockburst process in *** results show that the intensity of gneiss rockburst decreases with decrease of unloading rate,which is manifested as the reduction of AE energy and fragments ejection *** mechanisms are proposed to explain this effect:(i)The reduction of unloading rate changes the crack propagation mechanism in the process of *** makes the rockbursts change from the tensile failure mechanism at high unloading rate to the tension-shear mixed failure mechanism at low unloading rate,and more energy released in the form of shear crack ***,less strain energy is converted into kinetic energy of fragments ejection.(ii)Less plate cracking degree of gneiss has taken shape due to decrease of unloading rate,resulting in the destruction of rockburst incubation *** enlightenments of reducing the unloading rate for the project are also described *** rockburst magnitude is reduced from the medium magnitude at the unloading rate of 0.1 MPa/s to the slight magnitude at the unloading rate of 0.02. MPa/s,which was judged by the ejection velocity.

关键词： Rockburst Unloading rate Crack propagation Influence mechanisms

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Effects of seepage pressure on the mechanical behaviors and microstructure of sandstone

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第6期16卷 2033-2051页

作者： Xuewei Liu Juxiang Chen Bin Liu Sai Wang Quansheng Liu Jin Luo State Key Laboratory of geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China Faculty of Engineering China University of GeosciencesWuhan430074China Key Laboratory of Safety for Geotechnical and Structural Engineering of Hubei Province School of Civil EngineeringWuhan UniversityWuhan430072China

Surrounding rocks of underground engineering are subjected to long-term seepage pressure,which can deteriorate the mechanical properties and cause serious *** order to understand the impact of seepage pressure on the mechanical property of sandstone,uniaxial compression tests,P-wave velocity measurements,and nuclear magnetic resonance(NMR)tests were conducted on saturated sandstone samples with varied seepage pressures(i.e.0 MPa,3 MPa,4 MPa,5 MPa,6 MPa,7 MPa).The results demonstrate that the mechanical parameters(uniaxial compressive strength,peak strain,elastic modulus,and brittleness index),total energy,elastic strain energy,as well as elastic strain energy ratio,decrease with increasing seepage pressure,while the dissipation energy and dissipation energy ratio ***,as seepage pressure increases,the micro-pores gradually transform into meso-pores and *** increases the cumulative porosity of sandstone and decreases P-wave *** numerical results indicate that as seepage pressure rises,the number of tensile cracks increases progressively,the angle range of microcracks is basically from 50-12.to 80-100,and as a result,the failure mode transforms to the tensile-shear mixed failure ***,the effects of seepage pressure on mechanical properties were *** results show that decrease in the effective stress and cohesion under the action of seepage pressure could lead to deterioration of strength behaviors of sandstone.

关键词： Rock mechanics Mechanical property Seepage pressure Numerical simulation Microcracks

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基于铜污染太湖底泥的真空电渗脱水去污电极材料特性试验研究

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Journal of Central South University 2024年第3期31卷 827-840页

作者：李少宇沈扬戚文成陈锴嘉 Key Laboratory of Ministry of Education for geomechanics and Embankment Engineering Hohai UniversityNanjing 210098China

真空电渗法能够实现重金属污染底泥脱水去污一体化处理,本文通过自制真空电渗一体化室内模型试验系统,从排水量、沉降、电流、有效电势、污染物去除率、能耗等方面,对EKG、石墨、铝、铁、铜等五种材料作为电极在真空电渗方法处理铜污染... 详细信息

真空电渗法能够实现重金属污染底泥脱水去污一体化处理,本文通过自制真空电渗一体化室内模型试验系统,从排水量、沉降、电流、有效电势、污染物去除率、能耗等方面,对EKG、石墨、铝、铁、铜等五种材料作为电极在真空电渗方法处理铜污染太湖底泥过程中的表现进行分析。结果表明:选用铜作为电极材料具有最好的脱水效果但对铜污染去除效果较差,而选用EKG作为电极则具有最好的铜污染去除效果,且脱水效果仅次于铜,说明EKG材料在脱水去污一体化处理中的优越性。当选用金属作为电极材料时,阳极的电极腐蚀较为严重,很大程度上影响处理过程中真空电渗各项参数和处理效果。介入真空压力后,改变了传统电动修复过程中有效电势持续衰减的趋势,使有效电势在处理中后期出现回升,且回升程度受电极材料变形协调能力的影响。

关键词：真空预压电渗污染底泥电极材料铜污染

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Dynamic response mechanism and precursor characteristics of gneiss rockburst under different initial burial depths

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Journal of Mountain Science 2024年第3期21卷 1004-1018页

作者： LIU Dongqiao SUN Jie MENG Wen HE Manchao ZHANG Chongyuan LI Ran CAO Binghao State Key Laboratory for Tunnel Engineering China University of Mining and TechnologyBeijing 100083China Key Laboratory of Active Tectonics and Geological Safety Ministry of Natural ResourcesInstitute of GeomechanicsChinese Academy of Geological SciencesBeijing 100081China School of Mechanics and Civil Engineering China University of Mining and TechnologyBeijing 100083China

To investigate the influence mechanism of geostress on rockburst characteristics,three groups of gneiss rockburst experiments were conducted under different initial geostress conditions.A high-speed photography system and acoustic emission(AE)monitoring system were used to monitor the entire rockburst process in real *** experimental results show that when the initial burial depth increases from 92. m to 132. m,the proportion of large fracture scale in rockburst increases by 154.54%,and the AE energy increases by 565.63%,reflecting that the degree and severity of rockburst increase with the increase of burial *** then,two mechanisms are proposed to explain this effect,including(i)the increase of initial geostress improves the energy storage capacity of gneiss,and then,the excess energy which can be converted into kinetic energy of debris ejection increases,consequently,a more pronounced violent ejection phenomenon is observed at rockburst;(ii)the increase of initial geostress causes more sufficient plate cracks of gneiss after unloading ofσh,which provides a basis for more severe ejection of ***’s more,a precursor with clear physical meaning for rockburst is proposed under the framework of dynamic response process of crack ***,potential value in long term rockburst warning of the precursor obtained in this study is shown via the comparison of conventional precursor.

关键词： Traffic Engineering Gneiss Rockburst Crack propagation Excess energy Precursor characteristic

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