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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

Development and Deformation Characteristics of Large Ancient Landslides in the Intensely Hazardous Xiongba-Sela Section of the Jinsha River, Eastern Tibetan Plateau, China

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Journal of Earth Science 2024年第3期35卷 980-997页

作者： Yiqiu Yan Changbao Guo Yanan Zhang Zhendong Qiu Caihong Li Xue Li institute of geomechanics Chinese Academy of Geological SciencesBeijing 100081China Key Laboratory of Active Tectonics and Geological Safety Ministry of Natural ResourcesBeijing 100081China

The upstream Jinsha River,located in the eastern Tibetan Plateau,has been experiencing intense geological hazards characterized by a high density of ancient landslides,significant deformation and reactivation *** this study,remote sensing interpretation,field investigations,and Small Baseline Subset Interferometric Synthetic Aperture Radar(SBAS-InSAR)technologies have been *** a 17 km stretch of the Jinsha River,specifically in the Xiongba-Sela segment,16 large-scale ancient landslides were identified,9 of which are currently undergoing creeping ***,the Sela and Xiongba ancient landslides exhibit significant deformation,with a maximum deformation rate of-192.mm/yr,indicating a high level of sliding *** volume of the Sela ancient landslide is estimated to be 1.8×108 to 4.5×108 m3,and characterized by extensive fissures and long-term creeping *** SBAS-InSAR results revealed significant spatial variations in the deformation of the Sela ancient landslide,generally displaying two secondary zones of intense deformation,and landslide deformation exhibits nonlinear behavior with *** January 2.16 and February 2.2.,Zone III1 on the southwest side of the Sela ancient landslide,experienced a maximum cumulative deformation of-857 mm,with a maximum deformation rate of-108 mm/*** III2.on the northeast side of the Sela ancient landslide,the maximum cumulative deformation was-456 mm,with a maximum deformation rate of-74 mm/yr;among these,the H2.and H4 secondary bodies on the south side of III1 are in the accelerative deformation stage and at the Warn warning *** propose that the large-scale flood and debris flow disasters triggered by the Baige landslide-dammed lake-dam broken disaster chain in Tibetan Plateau during October and November 2.18 caused severe erosion at the foot of downstream *** far-field triggering effect accelerated the creep of the downstream ancient ***,the defo

关键词： Jinsha River SBAS-InSAR landslides surface deformation disasters.

Estimating shear strength of high-level pillars supported with cemented backfilling using the HoekeBrown strength criterion

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第2期16卷 454-469页

作者： Kaizong Xia Congxin Chen Xiumin Liu Yue Wang Xuanting Liu Jiahao Yuan State Key Laboratory of geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of Sciences Beijing100049China

Deep metal mines are often mined using the high-level pillars with subsequent cementation backfilling(HLSCB)mining *** the design stage,it is therefore important to have a reasonable method for determining the shear strength of the high-level pillars(*** and internal friction angle)when they are supported by cemented *** this study,a formula was derived for the upper limit of the confining pressure σ3max on a high-level pillar supported by cemented backfilling in a deep metal mine.A new method of estimating the shear strength of such pillars was then proposed based on the Hoek eBrown failure *** analysis indicates that the horizontal stress σhh acting on the cemented backfill pillar can be simplified by expressing it as a constant value.A reasonable and effective value for σ3max can then be *** value of s3max predicted using the proposed method is generally less than 3 *** this range,the shear strength of the high-level pillar is accurately calculated using the equivalent MohreCoulomb *** proposed method can effectively avoid the calculation of inaccurate shear strength values for the high-level pillars when the original HoekeBrown criterion is used in the presence of large confining pressures,*** situation in which the cohesion value is too large and the friction angle is too small can effectively be *** proposed method is applied to a deep metal mine in China that is being excavated using the HLSCB *** shear strength parameters of the high-level pillars obtained using the proposed method were input in the numerical *** numerical results show that the recommended level heights and sizes of the high-level pillars and rooms in the mine are rational.

关键词： Deep metal mines High-level pillars HoekeBrown strength criterion Cemented backfilling Confining pressure Shear strength

Thermal and exhumation history of the Songnan Low Uplift,Qiongdongnan Basin:constraints from the apatite fission-track and zircon(U-Th)/He thermochronology

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Acta Oceanologica Sinica 2024年第4期43卷 40-49页

作者： Xiaoyin Tang Kaixun Zhang Shuchun Yang Shuai Guo Xinyan Zhao Zhizhao Bai institute of geomechanics Chinese Academy of Geological SciencesBeijing 100081China Key Laboratory of Paleomagnetism and Tectonic Reconstruction Ministry of Natural ResourcesBeijing 100081China Key Laboratory of Petroleum geomechanics China Geological SurveyBeijing 100081China China National Offshore Oil Corporation(CNOOC)Research Center Beijing 100028China

Significant advancements have been made in the study of Mesozoic granite buried hills in the Songnan Low Uplift(SNLU)of the Qiongdongnan *** findings indicate that the bedrock buried hills in this basin hold great potential for *** samples taken from the granite buried hills in the SNLU were analyzed using apatite fission track(AFT)and zircon(U-Th)/He data to unravel the thermal history of the basement *** information is crucial for understanding the processes of exhumation and alteration that occurred after its *** modeling of a sample from the western bulge of the SNLU revealed a prolonged cooling event from the late Mesozoic to the Oligocene period(~80-2..8 Ma),followed by a heating stage from the Miocene epoch until the present(~2..8 Ma to present).In contrast,the sample from the eastern bulge experienced a more complex thermal *** underwent two cooling stages during the late Mesozoic to late Eocene period(~80-36.4 Ma)and the late Oligocene period(~30-2..8 Ma),interspersed with two heating phases during the late Eocene to early Oligocene period(~36.4-30 Ma)and the Miocene epoch to recent times(~2..8-0 Ma),*** differences in exhumation histories between the western and eastern bulges during the late Eocene to Oligocene period in the SNLU can likely be attributed to differences in fault *** typical passive continental margin basins,the SNLU has experienced accelerated subsidence after the rifting phase,which began around 5.2.Ma *** possible mechanism for this abnormal post-rifting subsidence may be the decay or movement of the deep thermal source and the rapid cooling of the ***-term and multi-episodic cooling and exhumation processes play a key role in the alteration of bedrock and contribute to the formation of *** the other hand,rapid post-rifting subsidence(sedimentation)promotes the formation of cap rocks.

关键词： granite buried hills (U-Th)/He dating fission-track dating exhumation Songnan Low Uplift

An improved elastoplastic model for rocks and application to cyclic loading and unloading triaxial compression tests

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Acta Mechanica Sinica 2024年第8期40卷 179-193页

作者： Qiuxin Gu Qiang Zhang Yapeng Li Peinan Wu Guilei Han State Key Laboratory for geomechanics and Deep Underground Engineering School of Mechanics and Civil EngineeringChina University of Mining and TechnologyXuzhou221116China North China Engineering Investigation institute Shijiazhuang050021China

The recoverable strain of rock is completely classified as elastic strain in the conventional elastic-plastic theory,which often results in poor agreement between theoretical and experimental *** work proposes an improved elastoplastic model of rock materials considering the evolutions of crack deformation and elastic modulus to better characterize the nonlinear mechanical behavior of rock in the post-peak *** this model,the recoverable strain is assumed to be a combination of elastic and crack strain,and the constitutive relationship between crack strain and rock stress is *** on the proposed assumption,the evolutions of the mechanical parameters including strength parameters,elastic,plastic,and crack deformation parameters versus the plastic strain and confining stress were *** developed elastoplastic model was validated by comparing the theoretical values with the results of the triaxial cyclic loading and unloading *** theoretical calculation results show a good agreement with the laboratory test,which indicates that the improved elastoplastic model can effectively reflect the nonlinear mechanical behavior of the rock *** research results are expected to provide a valuable reference for further understanding the evolution of rock crack deformation.

关键词： Crack strain Elastic modulus deterioration Novel elastoplastic model Model validation

Swelling pressure evolution characterization of strong expansive soil considering the influence of reserved expansion deformation

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Journal of Mountain Science 2024年第1期21卷 252-270页

作者： LI Tianguo KONG Lingwei GUO Aiguo YAN Junbiao 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

Numerous engineering cases have demonstrated that the expansive soil channel slope remains susceptible to damage with the implementation of a rigid or closed protective structure. It is common for the protective structure to experience bulging failure due to excessive swelling pressure. To investigate the swelling pressure properties of expansive soil, the constant volume test was employed to study the influence of water content and reserved expansion deformation on the characteristics of swelling pressure in strong expansive soils, and also to explore the evolution mechanism of the swelling pressure. The findings demonstrate that the swelling pressure-time curve can be classified into swelling pressure-time softening and swelling pressure-time stability type. The swelling pressuretime curve of the specimen with low water content is the swelling pressure-time softening type, and the softening level will be weakened with increasing reserved expansion deformation. Besides, the maximum swelling pressure Psmax decreases with increasing water content and reserved expansion deformation, especially for expansion ratio η from 2.% to 37%. The reserved deformation has little effect on reducing Psmax when it is beyond 7% of the expansion rate. The specimen with low water content has a more homogeneous structure due to the significant expansion-filling effect, and the fracture and reorganization of the aggregates in the specimens with low water content cause the swelling pressure-time softening behavior. In addition, the proposed swelling pressure-time curve prediction model has a good prediction on the test results. If necessary, a deformation space of about 7% expansion rate is recommended to be reserved in the engineering to reduce the swelling pressure except for keeping a stable water content.

关键词： Expansive soil Swelling pressure Reserved expansion deformation Water content

Experimental study on the effect of flexible joints of a deep-buried tunnel across an active fault under high in-situ stress conditions

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Underground Space 2024年第6期19卷 189-207页

作者： Jiawei Zhang Zhen Cui Qian Sheng Wanhua Zhao Liang Song State Key Laboratory of geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China School of Civil Engineering and Architecture Wuhan Polytechnic UniversityWuhan 430023China

During dislocation,a tunnel crossing the active fault will be damaged to varying degrees due to its permanent stratum *** previous studies did not consider the influence of the tunnel’s deep burial and the high in-situ stress,so the results were not entirely *** this paper,the necessity of solving the anti-dislocation problem of deep-buried tunnels is systemically *** the model test of tunnels across active faults,the differences in failures between deep-buried tunnels and shallow-buried tunnels were compared,and the dislocation test of deep-buried segmental tunnels was carried out to analyze the external stress change,lining strain,and failure mode of *** results are as follows.(1)The overall deformation of deep-buried and shallow-buried tunnels is both *** failure mode of deep-buried tunnels is primarily characterized by shear and tensile failure,resulting in significant compressive deformation and a larger damaged *** contrast,shallow-buried tunnels mainly experience shear failure,with the tunnel being sheared apart at the fault crossing,leading to more severe damage.(2.After the segmental structure design of the deep-buried tunnel,the‘‘S”deformation pattern is transformed into a‘‘ladder”pattern,and the strain of the tunnel and the peak stress of the external rock mass are reduced;therefore,damages are significantly mitigated.(3)Through the analysis of the distribution of cracks in the tunnel lining,it is found that the tunnel without a segmental structure design has suffered from penetrating failure and that cracks affect the entire *** cracks in a flexible segmental tunnel affect about 66.6%of the entire length of the tunnel,and cracks in a tunnel with a short segmental tunnel only affect about 33.3%of the entire length of the ***,a deep-buried tunnel with a short segmental tunnel can yield a better anti-dislocation effect.(4)By comparing the shallow-buried segmental tunnel in previous

关键词： Tunnel project Crossing active fault High in-situ stress Segmental structure design Flexible joint

Effect of coral sand on the mechanical properties and hydration mechanism of magnesium potassium phosphate cement mortar

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第2期25卷 116-129页

作者： Hao LIU Huamei YANG Houzhen WEI Jining YU Qingshan MENG Rongtao YAN College of Civil Engineering and Architecture Guilin University of TechnologyGuilin541004China Guangxi Key Laboratory of geomechanics and Geotechnical Engineering Guilin University of TechnologyGuilin541004China State Key Laboratory of geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China School of Intelligent Construction Wuchang University of TechnologyWuhan430002China Hydraulic Concrete institute China Three Gorges CorporationBeijing100038China The First Railway Survey and Design institute Group Corporation Xi’an710043China

Damaged structures on coral islands have been spalling and cracking due to the dual corrosion of tides and *** ensure easy access to aggregate materials,magnesium potassium phosphate cement(MKPC)and coral sand(CS)are mixed to repair damaged structures on coral ***,CS is significantly different from land-sourced sand in mineral composition,particle morphology,and *** has a substantial impact on the hydration characteristics and macroscopic properties of MKPC ***,in this study we investigated the compressive strength,interfacial mechanical properties,and corrosion resistance of MKPC CS *** in the morphology,microstructure,and relative contents of hydration products were revealed by scanning electron microscope-energy dispersive spectrometer(SEM-EDS)and X-ray diffraction(XRD).The results indicated that the compressive strength increased linearly with the interfacial micro-hardness,and then stabilized after long-term immersion in pure water and Na2.O4 solution,showing excellent corrosion *** with MKPC river sand(RS)mortar,the hydration products of CS mortar were an intermediate product 6KPO2.8H2. with a relative content of 3.9%at 1 h and 4.1%at 12.*** hydration product MgKPO_(4)·6H_(2.O increased rapidly after 7-d curing,with an increased growth rate of 1100%.Our results showed that CS promoted the nucleation and formation of hydration products of MKPC,resulting in better crystallinity,tighter overlapping,and a denser interfacial transition *** results of this study provide technical support for applying MKPC mortar as a rapid repair material for damaged structures on coral islands.

关键词： Magnesium potassium phosphate cement(MKPC) Coral sand(CS) Mechanical properties Corrosion resistance Hydration mechanism

Real-time arrival picking of rock microfracture signals based on convolutional-recurrent neural network and its engineering application

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第3期16卷 761-777页

作者： Bing-Rui Chen Xu Wang Xinhao Zhu Qing Wang Houlin Xie State Key Laboratory of geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of Sciences Beijing100049China

Accurately picking P-and S-wave arrivals of microseismic(MS)signals in real-time directly influences the early warning of rock mass failure.A common contradiction between accuracy and computation exists in the current arrival picking ***,a real-time arrival picking method of MS signals is constructed based on a convolutional-recurrent neural network(CRNN).This method fully utilizes the advantages of convolutional layers and gated recurrent units(GRU)in extracting short-and long-term features,in order to create a precise and lightweight arrival picking ***,the synthetic signals with field noises are used to evaluate the hyperparameters of the CRNN model and obtain an optimal CRNN *** actual operation on various devices indicates that compared with the U-Net method,the CRNN method achieves faster arrival picking with less performance *** application of large underground caverns in the Yebatan hydropower station(YBT)project shows that compared with the short-term average/long-term average(STA/LTA),Akaike information criterion(AIC)and U-Net methods,the CRNN method has the highest accuracy within four sampling points,which is 87.44%for P-wave and 91.2.%for S-wave,*** sum of mean absolute errors(MAESUM)of the CRNN method is 4.2. sampling points,which is lower than that of the other *** the four methods,the MS sources location calculated based on the CRNN method shows the best consistency with the actual failure,which occurs at the junction of the shaft and the second ***,the proposed method can pick up P-and S-arrival accurately and rapidly,providing a reference for rock failure analysis and evaluation in engineering applications.

关键词： Rock mass failure Microseismic event P-wave arrival S-wave arrival Deep learning