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Impacts of Disk Rock Sample Geometric Dimensions on shear Fracture behavior in a Punch shear Test

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Computer Modeling in Engineering & Sciences 2021年第2期126卷 457-477页

作者： Tantan Zhu Yao Li School of Highway Chang’an UniversityXi’an710064China

Punch shear tests have been widely used to determine rock shear mechanical properties but without a standard sample geometric dimension *** investigate the impacts of sample geometric dimensions on shear behaviors in a punch shear test,simulations using Particle Flow Code were carried *** effects of three geometric dimensions(i.e.,disk diameter,ratio of shear surface diameter to disk diameter,and ratio of disk height to shear surface diameter)were *** of shear strength,shear stiffness,and shear dilatancy angles were studied,and the fracture processes and patterns of samples were ***,normal stress on the shear surface during test was analyzed and a suggested disk geometric dimension was *** results show that when the ratio of the shear surface diameter to the disk diameter and the ratio of disk height to the shear surface diameter is small enough,the shear strength,shear stiffness,and shear dilatancy angles are extremely sensitive to the three geometric *** the ratio of surface diameter to disk diameter is too large or the ratio of disk height to surface diameter is too small,a part of the sample within the shear surface will fail due to macro tensile cracks,which is characterized by break *** with a greater ratio of disk height to shear surface diameter,namely when the sample is relatively thick,crack from one end to the other while others crack from both ends towards the *** test,the actual normal stress on the shear surface is greater than the target value because of the extra compressive stress from the part of sample outside shear surface.

关键词： Punch shear test shear behavior suggested geometric dimensions particle flow code simulation fracture process

Changes in shear properties of granite fractures subjected to cyclic heating and air-cooling treatments

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第12期16卷 4925-4943页

作者： Guo-Hua Zhang Zhao-Yang Han Sheng-Lian Li Lu-Zhao Dan Feng Xiong Zhi-Cheng Tang Factory of Engineering China University of GeosciencesWuhan430074HubeiChina Key Laboratory of Geological Survey and Evaluation of Ministry of Education China University of GeosciencesWuhan430074HubeiChina Yunnan Infrastructure Investment Co. Ltd.Kunming650032YunnanChina Yunnan Communications Investment&Construction Group Co. Ltd.Kunming650032YunnanChina

The effects of cyclic heat treatments on the fracture shear behaviors are rarely *** enhance our understanding,granite fractures having almost the same roughness were first exposed to cyclic heating at 400C and air-cooling treatments,and then direct shear tests were performed under four levels of normal *** influences of thermal cycles on roughness degradation and shear properties are *** roughness degradation in the joint roughness coefficient and the three-dimensional(3D)roughness metric exhibit linear increasing tendency with increasing thermal *** fracture shear properties,including cohesion and friction angle,peak and residual shear strength,peak and residual shear displacement,and initial and secant shear stiffness,fluctuate generally within the first 10 thermal cycles,followed by gradual decreasing *** thermal effect on the shear properties become weaker as the number of heat treatments increases from 10 to *** expansion and shrinkage of mineral grains after thermal treatments produce micro-cracks within the rock matrix and on the rock surface,suggesting that asperities are easier to be *** alteration in fracture peak-shear strength could be attributed to the deterioration in rock strengths and the mismatch in opposing fracture *** observations would provide better insights into rock friction after high temperatures in geothermal energy exploitation.

关键词： Granite fracture Cyclic thermal treatment Roughness degradation shear behavior Thermodynamic mechanism

shear mechanical properties and energy evolution of rock-like samples containing multiple combinations of non-persistent joints

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第7期15卷 1651-1670页

作者： Daping Tai Shengwen Qi Bowen Zheng Chonglang Wang Songfeng Guo Guangming Luo Key Laboratory of Shale Gas and Geoengineering Institute of Geology and GeophysicsChinese Academy of SciencesBeijing100029China University of Chinese Academy of Sciences Beijing100049China Innovation Academy for Earth Science Chinese Academy of SciencesBeijing100029China China-Pakistan Joint Research Center on Earth Sciences CAS-HECIslamabad45320Pakistan Department of Civil and Mineral Engineering University of TorontoTorontoOntarioM5S 1A4Canada

Discontinuities are often considered as important factors responsible for the instability caused by shear failure in engineering rock mass,and energy-driven instability is the root cause of rock ***,few studies focus on the energy evolution during the failure process using a three-dimensional(3D)numerical *** this study,a series of laboratory direct shear tests on rock-like samples is numer-ically simulated using bonded particle models(BPMs)with multiple combinations of discontinuous in the particle flow code(PFC3D),in which the location and size of the particles conform to the uniform *** effects of joint row number and inclination on the stress-strain characteristics and failure mode of rock were studied from the perspective of microcrack growth and energy *** results showed that,when the number of joint rows Nr>1,the shear failure region does not change with the increase of Nr for the type B(2-columnn multiple-row at center)and the type C(2-column multiple-row at edge)as compared to the type A(1-column multiple-row at center)joint ***,joints significantly increase the post-peak energy dissipation but have little effect on the proportion of energy before the *** consumes most of the energy while kinetic energy accounts for less than 1%of total energy during the shear *** elastic strain energy follows the variation trend of peak shear *** development and accumulation of microcracks directly affect the energy dissipation,and there is a significant linear relationship between the cumulative number of critical microcracks and the critical dissipated energy at the failure,when the dip direction of joints is opposite to the shear direction,more microcracks will be accumulated at the peak time,resulting in more energy *** results contribute to deeply understanding the shear failure process of non-persistent jointed mass.

关键词： Non-persistent joints shear behavior Energy evolution Particle flow code(PFC3D)

Numerical simulation study on shear resistance of anchorage joints considering tensile-shear fracture criterion of 2G-NPR bolt

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International Journal of Coal Science & Technology 2023年第4期10卷 186-202页

作者： Shulin Ren Zhigang Tao Manchao He Mengnan Li Qiru Sui State Key Laboratory for Geomechanics and Deep Underground Engineering Beijing 100083China School of Mechanics and Civil Engineering China University of Mining and TechnologyBeijing 100083China

2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock mass and controlling the stability of surrounding rock. To achieve an accurate simulation of bolted joint shear tests, we have studied a numerical simulation method that takes into account the 2G-NPR bolt's tensile–shear fracture criterion. Firstly, the indoor experimental study on the tensile–shear mechanical properties of 2G-NPR bolt is carried out to explore its mechanical properties under diferent tensile–shear angles, and the fracture criterion of 2G-NPR bolt considering the tensile–shear angle is established. Then, a three-dimensional numerical simulation method considering the tensile–shear mechanical constitutive and fracture criterion of 2G-NPR bolt, the elastoplastic mechanical behavior of surrounding rock and the damage and deterioration of grouting body is proposed. The feasibility and accuracy of the method are verifed by comparing with the indoor shear test results of 2G-NPR bolt anchorage joints. Finally, based on the numerical simulation results, the deformation and stress of the bolt, the distribution of the plastic zone of the rock mass, the stress distribution and the damage of the grouting body are analyzed in detail. The research results can provide a good reference value for the practical engineering application and shear mechanical performance analysis of 2G-NPR bolt.

关键词： Anchorage joints 2G-NPR bolt Tensile-shear fracture criterion shear behavior Numerical simulation

Experimental study on the seismic performance of new sandwich masonry walls

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Earthquake Engineering and Engineering Vibration 2013年第1期12卷 77-86页

作者： Xiao Jianzhuang Pu Jie Hu Yongzhong Department of Building Engineering Tongji University State Key Laboratory for Disaster Reduction in Civil Eng. Tongji University

Sandwich masonry walls are widely used as energy-saving panels since the interlayer between the outer leaves can act as an insulation *** types of sandwich walls are continually being introduced in research and applications,and due to their unique bond patterns,experimental studies have been performed to investigate their mechanical properties,especially with regard to their seismic *** this study,three new types of sandwich masonry wall have been designed,and cyclic lateral loading tests were carried out on five *** results showed that the specimens failed mainly due to slippage along the bottom cracks or the development of diagonal cracks,and the failure patterns were considerably influenced by the aspect *** was undertaken on the seismic response of the new walls,which included ductility,stiffness degradation and energy dissipation capacity,and no obvious difference was observed between the seismic performance of the new walls and traditional *** were made between the experimental results and the calculated results of the shear *** is concluded that the formulas in the two Chinese codes（GB 50011 and GB 50003） are suitable for the calculation of the shear capacity for the new types of walls,and the formula in GB 50011 tends to be more conservative.

关键词： sandwich wall seismic performance shear behavior cyclic loading test

Experimental study on mechanical properties of basalt fiber-reinforced silty clay

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Journal of Central South University 2022年第6期29卷 1945-1956页

作者： JIA Yu ZHANG Jia-sheng WANG Xuan DING Yu CHEN Xiao-bin LIU Tao Geotechnical Engineering School of Civil EngineeringCentral South UniversityChangsha 410083China National Engineering Research Center of High-Speed Railway Construction Technology Central South UniversityChangsha 410083China China Railway Siyuan Survey and Design Group Co. Ltd.Wuhan 430060China

Fiber reinforcement technology can significantly improve the mechanical properties of soil and has been increasingly applied in geotechnical *** fiber is a new kind of environment-friendly and highperformance soil reinforcement material,and the mechanical properties of basalt fiber-reinforced soil have become a hot research *** this paper,we conducted monotonic triaxial and cyclic triaxial tests,and analyzed the influence of the fiber content,moisture content,and confining pressure on the shear characteristics,dynamic modulus,and damping ratio of basalt fiber-reinforced silty *** results illustrate that basalt fiber can enhance the shear strength of silty clay by increasing its *** find that the shear strength of reinforced silty clay reaches its maximum when the fiber content is approximately 0.2%and the moisture content is 18.5%(optimum moisture content).Similarly,we also find that the dynamic modulus that corresponds to the same strain first increases then decreases with increasing fiber content and moisture content and reaches its maximum when the fiber content is approximately 0.2%and the moisture content is 18.5%.The dynamic modulus is positively correlated with the confining ***,the change in the damping ratio with fiber content,moisture content,and confining pressure is opposite to that of the dynamic *** can be concluded that the optimum content of basalt fiber for use in silty clay is 0.2%.After our experiments,we used scanning electron microscope(SEM)to observe the microstructure of specimens with different fiber contents,and our results show that the gripping effect and binding effect are the main mechanisms of fiber reinforcement.

关键词： basalt fiber-reinforced silty clay shear behavior dynamic modulus damping ratio optimum fiber content