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Cyclic shear behavior of en-echelon joints under constant normal stiffness conditions

Journal of Rock Mechanics and Geotechnical Engineering 2024年第9期16卷 3419-3436页

作者： Bin Wang Yujing Jiang Qiangyong Zhang Hongbin Chen Richeng Liu Yuanchao Zhang Graduate School of Engineering Nagasaki UniversityNagasaki852-8521Japan Research Center of Geotechnical and Structural Engineering Shandong UniversityJi’nan250061China State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou221116China College of Civil Engineering Fuzhou UniversityFuzhou350108China

To reveal the mechanism of shear failure of en-echelon joints under cyclic loading,such as during earthquakes,we conducted a series of cyclic shear tests of en-echelon joints under constant normal stiffness(CNS)*** analyzed the evolution of shear stress,normal stress,stress path,dilatancy characteristics,and friction coefficient and revealed the failure mechanisms of en-echelon joints at different *** results show that the cyclic shear behavior of the en-echelon joints is closely related to the joint angle,with the shear strength at a positive angle exceeding that at a negative angle during shear *** the number of cycles increases,the shear strength decreases rapidly,and the difference between the varying angles gradually *** occurs in the early shear cycles(1 and 2),while contraction is the main feature in later cycles(310).The friction coefficient decreases with the number of cycles and exhibits a more significant sensitivity to joint angles than shear *** joint angle determines the asperities on the rupture surfaces and the block size,and thus determines the subsequent shear failure mode(block crushing and asperity degradation).At positive angles,block size is more greater and asperities on the rupture surface are smaller than at nonpositive ***,the cyclic shear behavior is controlled by block crushing at positive angles and asperity degradation at negative angles.

关键词： En-echelon joint Cyclic shear tests Shear stress normal displacement Constant normal stiffness(CNS)

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Experimental study on unloading induced shear performances of 3D saw-tooth rock fractures

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International Journal of Mining Science and Technology 2023年第4期33卷 463-479页

作者： Qian Yin Xinxin Nie Jiangyu Wu Qi Wang Kaiqi Bian Hongwen Jing State Key Laboratory for Geomechanics&Deep Underground Engineering China University of Mining and TechnologyXuzhou 221116China State Key Laboratory of High Performance Civil Engineering Materials Jiangsu Research Institute of Building Science Co.Ltd.Nanjing 210008China Department of Materials University of OxfordOxford OX13PHUK State Key Laboratory for Geomechanics&Deep Underground Engineering China University of Mining and Technology-BeijingBeijing 100083China

A fractal model governing saw-tooth fractures was first introduced to replicate sandstone samples containing an inclined 3D penetrating rough fracture surface with various joint roughness coefficients(JRC).In conventional triaxial compression,the peak strength for fractured samples increased with both confining pressure and *** the unloading confining pressure process,the normal stress of fractures declined but the shear stress increased,resulting in shear sliding of *** shear displacement of fractures exponentially increased,and the positive normal displacement decreased gradually to negative values under coupling effects of shear contraction caused by normal stress and shear dilation due to climbing effects of *** from quasi-static to dynamic sliding of the fractures was *** sliding resistance duration increased with confining pressure but decreased with *** prepeak unloading,the fracture surfaces presented a more significant surface wear response and JRC values decreased by 1.70%–59.20%due to more remarkable asperity degradation compared with those after conventional triaxial *** theoretical model for shear strength of fractures was established through improving the Ladanyi&Archambault model by introducing the relations between normal stress and surface wear ratios of fractures,which agreed well with the experimental results.

关键词： Saw-tooth fracture surfaces Pre-peak unloading Shear sliding normal displacement JRC values

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Shear sliding of rough-walled fracture surfaces under unloading normal stress

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第10期15卷 2658-2675页

作者： Qian Yin Chun Zhu Jiangyu Wu Hai Pu Qi Wang Yuanchao Zhang Hongwen Jing Tianci Deng State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou221116China School of Earth Sciences and Engineering Hohai UniversityNanjing210098China State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of TechnologyChengdu610059China State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and Technology(Beijing)Beijing100083China College of Civil Engineering Fuzhou UniversityFuzhou350108China

Through high-precision engraving,self-affine sandstone joint surfaces with various joint roughness coefficients(JRC=3.21e12.16)were replicated and the shear sliding tests under unloading normal stress were conducted regarding various initial normal stresses(1e7 MPa)and numbers of shearing cycles(1 e5).The peak shear stress of fractures decreased with shear cycles due to progressively smooth surface morphologies,while increased with both JRC and initial normal stress and could be verified using the nonlinear Barton-Bandis failure *** joint friction angle of fractures exponentially increased by 62.22%e64.87%with JRC while decreased by 22.1%e24.85%with shearing *** unloading normal stress,the sliding initiation time of fractures increased with both JRC and initial normal stress due to more tortuous fracture morphologies and enhanced shearing resistance *** surface resistance index(SRI)of fractures decreased by 4.35%e32.02%with increasing shearing cycles due to a more significant reduction of sliding initiation shear stress than that for sliding initiation normal stress,but increased by a factor of 0.41e1.64 with *** sliding initiation,the shear displacement of fractures showed an increase in power *** defining a sliding rate threshold of 5105 m/s,transition from“quasi-static”to“dynamic”sliding of fractures was identified,and the increase of sliding acceleration steepened with JRC while slowed down with shearing *** normal displacement experienced a slight increase before shear sliding due to deformation recovery as the unloading stress was unloaded,and then enhanced shear dilation after sliding initiation due to climbing effects of surface *** was positively related to the shear sliding velocity of *** characteristics of the fracture surfaces after shearing failure were evaluated using binary calculation,indicating an increasing shear area ratio by 45.24%e91.02%with normal stress.

关键词： Unloading normal stress Rough fracture surface Shear sliding normal displacement Shear wear characteristics

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The Frictional Coefficient of Bovine Knee Articular Cartilage

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Journal of Bionic Engineering 2006年第2期3卷 79-85页

作者： Qian Shan-hua Ge Shi-rong Wang Qing-liang College of Materials Science and Engineering China University of Mining Technology Xuzhou 221008 P. R. China

The normal displacement of articular cartilage was measured under load and in sliding, and the coefficient of friction during sliding was measured using a UMT-2 Multi-Specimen Test System. The maximum normal displacement under load and the start-up frictional coefficient have similar tendency of variation with loading time. The sliding speed does not significantly influence the frictional coefficient of articular cartilage.

关键词： articular cartilage normal displacement coefficient of start-up friction

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Relationship between Timing Jitter and Prism Separation in Mode-locked Solid State Lasers

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Chinese Journal of Lasers 2001年第5期 9-13页

作者： LU Hong (The Femtosecond Technology Research Association(FESTA), 1 1 4 Umezono, Tsukuba, Ibaraki 305 8568, Japan)

The function expression of the group delay dispersion (GDD) depending on the prism separation and the normal displacement is derived, and that the GDD is proportional to the prism separation and near to a linear function of the normal displacement in the case of small normal displacement are found Then we discuss the timing jitter caused by the amplified spontaneous emission (ASE) which depends on the prism separation and the normal displacement We find that the timing jitter is near to a linear function of the prism separation and can be regrded as a linear function of the normal displacement in the case of small normal displacement Based on the theoretic work, we suggest an experimental setup to measure the relationship between the timing jitter and the prism separation or the normal displacement

关键词： timing jitter prism separation normal displacement mode locked solid state lasers

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