scholarly journals Strength Characteristics of Nonpenetrating Joint Rock Mass under Different Shear Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Qingzhi Chen ◽  
Yuanming Liu ◽  
Shaoyun Pu
Keyword(s):  
Rock Mass ◽  
Normal Stress ◽  
Direct Shear Test ◽  
Shear Test ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Strength Characteristics ◽  
Triaxial Tests ◽  
Direct Shear ◽  
Rock Specimens

The mechanical property of jointed rock mass is an important factor to be considered in the analysis, evaluation, and design of actual rock engineering. The existence of joints threatens the stability and safety of underground engineering projects built in the rock mass. In order to study the change of mechanical properties and strength characteristics of nonpenetrating jointed rock mass under different test conditions, direct shear tests and triaxial tests were carried out. Direct shear tests under different normal stresses were carried out for nonpenetrating jointed rock mass to prepare specimens for triaxial tests. Then, triaxial tests were carried out to study the change of mechanical properties and strength characteristics of the nonpenetrating jointed rock mass. In the direct shear test part, the greater the normal stress is, the stronger the shear strength and the more serious the shear failure would be. The main conclusions are as follows: (1) the strength of rock mass would increase with the increase of confining pressure for those rock specimens with same degrees of shear after the direct shear test; (2) for rock specimens with different degrees of shear after the direct shear test, if the shearing degree of the rock specimen was greater, the strength of the rock specimen would be lower in the triaxial test; (3) for rock specimens with the same damage degree after direct shear test, the greater the normal stress in direct shear test is, the smaller the peak axial pressure would be in the triaxial test; (4) if the specimen was sheared under higher normal stress in direct shear test, the cohesion of it would be lower and the internal friction angle would be larger. For the specimens under the same normal stress, if the shear failure of one specimen was more serious, the cohesion of it would be smaller and the internal friction angle would be larger.

Influence of Dilation on the Axial Load of Bolt as Joint Subjected to Shearing

2013 ◽  
Vol 405-408 ◽  
pp. 326-330
Author(s):  
Wen Qiang Chen ◽  
Zhi Xin Jia ◽  
Yu Fei Zhao ◽  
Ji Jun Zhou ◽  
Xing Chao Lin
Keyword(s):  
Rock Mass ◽  
Normal Stress ◽  
Axial Load ◽  
Direct Shear Test ◽  
Shear Test ◽  
Load Transfer ◽  
Failure Zone ◽  
Direct Shear ◽  
Load Transfer Mechanism ◽  
The Relationship

Based on the load transfer mechanism of bolts, the relationship between the axial load and shear displacement of bolt changing with the dilatancy of joint was analyzed, then the theoretical solutions of axial load of the bolt were verified by the direct shear test of bolted rock mass with different normal stress (0.5MPa, 0.7MPa, 1.0MPa) applied on the joint. The results show that the calculated values fit well with the results of tests; the increment of dilation angle can enhance the axial force of bolt quickly, but decrease the length of crushing failure zone.

scholarly journals Research on the Strength Characteristics and Crack Propagation Law of Noncoplanar Nonthrough Jointed Rock Mass by PFC2D

2021 ◽  
Vol 2021 ◽  
pp. 1-28
Author(s):  
Qingzhi Chen ◽  
Yuanming Liu ◽  
Shilong Mei ◽  
Kai Cao ◽  
Bin Du ◽  
...  
Keyword(s):  
Rock Mass ◽  
Numerical Models ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Strength Characteristics ◽  
Particle Flow Code ◽  
Direct Shear ◽  
Direct Shear Tests ◽  
Relief Angle ◽  
Propagation Law

In this study, five groups of numerical models with different conditions were established by using PFC2D (particle flow code) to simulate the direct shear tests of noncoplanar nonthrough jointed rock mass. It is proved that normal stress and shear rate, as well as the connectivity rate, relief angle, and inclination angle of joints, have significant influence on the strength characteristics, number of cracks, and the stress of the rock mass according to measurement taken at five different measurement circles in the rock mass. Moreover, it is determined that in the process of shearing, no matter which group of tests are conducted, the number of cracks in the rock mass caused by tension is far more than that caused by the shear action. In other words, the failure of rock mass with different planes and discontinuous joints is mainly caused by the tension in the process of the direct shear test.

scholarly journals Effect of Rock Particle Content on the Mechanical Behavior of a Soil-Rock Mixture (SRM) via Large-Scale Direct Shear Test

2019 ◽  
Vol 2019 ◽  
pp. 1-16
Author(s):  
Longqi Liu ◽  
Xuesong Mao ◽  
Yajun Xiao ◽  
Qian Wu ◽  
Ke Tang ◽  
...  
Keyword(s):  
Shear Strength ◽  
Normal Stress ◽  
Large Scale ◽  
Direct Shear Test ◽  
Shear Test ◽  
Volumetric Strain ◽  
Direct Shear ◽  
Stress Strain ◽  
Particle Content ◽  
Rock Particle

The mechanical strength of the landslide deposits directly affects the safety and operation of the roads in the western mountainous area of China. Therefore, the research is aimed at studying the mechanisms of a landslide deposit sample with different rock particle contents by analyzing its characteristics of the stress-strain behavior, the “jumping” phenomenon, the volumetric strain, and the shear strength parameters via a large-scale direct shear test. Stress-strain results show that stress-strain curves can be divided into 3 different stages: liner elastic stage, yielding stage, and strain-hardening stage. The shear strength of SRM behaves more like “soil” at a lower rock particle content and behaves more like “rock joints” at a higher rock particle content. Characteristics of the “jumping” phenomenon results show that the “intense jumping” stage becomes obvious with the increasing rock particle content and the normal stress. However, the lower the rock particle content is, the more obvious the “jumping” phenomenon under the same normal stress is. Volumetric strain results show that the sample with a lower rock particle content showed a dilatancy behavior under the low normal stress and shrinkage behavior under the high normal stress. The dilatancy value becomes smaller with the increasing normal stress. The maximum shear stress value of the rock particle content corresponds to the maximum value of dilatancy or shrinkage. We also conclude that the intercept of the Mohr failure envelope of the soil-rock mixture should be called the “equivalent cohesion,” not simply called the “cohesion.” The higher the normal stress and rock particle content are, the bigger the equivalent cohesion and the internal friction angle is.

scholarly journals Experimental Study on Influence of Joint Surface Morphology on Strength and Deformation of Nonthrough Jointed Rock Masses under Direct Shear

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Yuanming Liu ◽  
Qingzhi Chen ◽  
Huiyu Chen ◽  
Xun Ou ◽  
Dafu Wu ◽  
...  
Keyword(s):  
Shear Strength ◽  
Rock Mass ◽  
Normal Stress ◽  
Failure Mode ◽  
Jointed Rock ◽  
Tangential Displacement ◽  
Direct Shear ◽  
Jointed Rock Masses ◽  
Final Failure ◽  
Joint Morphology

Direct shear tests were carried out on nonthrough jointed rock masses (NTJRM) with three types of joints under five normal stresses. The strength characteristics of shear strength, initial crack strength, and residual strength and the deformation characteristics of tangential displacement and dilatancy displacement as well as the transformation of failure mode and the variation of shear parameters of rock mass with different joint morphology are studied. Under the same normal stress, with the increase of joint undulation, the shear strength of NTJRM increases, and the corresponding tangential displacement of NTJRM increases. Two typical failure modes are observed: TTTS mode and TSSS mode. TTTS model indicates that the initial failure, extension failure, and final failure of rock mass are caused by tensile action, while the failure mode of through plane is formed by shear action. The initial failure of TSSS mode rock mass is caused by tensile action, while the expansion and final failure are caused by shear action, and the failure mode of through plane is formed under shear action. When the joint undulation is small and the normal stress is small, NTJRM will fail in TTTS mode; when the joint undulation is large and the normal stress is large, NTJRM will fail in TSSS mode. The results show that the shear parameters of NTJRM are related to the joint morphology, the bond force increases with the increase of joint undulation, and the internal friction angle increases with the increase of joint undulation. The research results of direct shear test of nonthrough jointed rock mass can provide reference for related research.

Evaluation of the anisotropy and directionality of a jointed rock mass under numerical direct shear tests

2017 ◽  
Vol 225 ◽  
pp. 29-41 ◽  
Author(s):  
Peitao Wang ◽  
Fenhua Ren ◽  
Shengjun Miao ◽  
Meifeng Cai ◽  
Tianhong Yang
Keyword(s):  
Rock Mass ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests

scholarly journals Investigation of the Shear Mechanical Behavior of Sandstone with Unloading Normal Stress after Freezing–Thawing Cycles

Machines ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 339
Author(s):  
Shuailong Lian ◽  
Jiashen Li ◽  
Fei Gan ◽  
Jing Bi ◽  
Chaolin Wang ◽  
...  
Keyword(s):  
Fracture Surface ◽  
Mechanical Behavior ◽  
Normal Stress ◽  
Direct Shear Test ◽  
Shear Test ◽  
Shear Displacement ◽  
Normal Displacement ◽  
Direct Shear ◽  
Thawing Cycle ◽  
Unloading Rate

Freezing–thawing action has a great impact on the physical and mechanical deterioration processes of rock materials in cold areas where environmental changes are very complicated. The direct shear test under unloading normal stress was adopted to investigate the shear mechanical behavior of sandstone samples after a freezing–thawing cycle in this paper. The failure shear displacement (Dsf), the failure normal displacement (Dnf), the shear displacement of unloading (Dsu), and the normal displacement of unloading (Dnu) were analyzed to describe the evolution of shear and normal deformation during the test. The results indicated that the shear displacement increased as the freezing–thawing cycle duration increased in a direct shear test under unloading normal stress. The unloading rate and the number of freezing–thawing cycles affected the failure pattern of the rock sample significantly in both the direct shear test under unloading normal stress and the direct shear test. The three-dimensional inclination angle, the distortion coefficient, and the roughness correlation coefficient of the fracture surface are dependent on the number of freezing–thawing cycles and the unloading rate. The surface average gradient mode of the fracture surface decreased as the freezing–thawing cycle times and unloading rate rose.

Analysis of the Deformation Field in the Direct Shear Test with Use of DPDM

2013 ◽  
Vol 275-277 ◽  
pp. 1503-1509
Author(s):  
Jie Zhang ◽  
Wen Bai Liu ◽  
Li Juan Su
Keyword(s):  
Normal Stress ◽  
Direct Shear Test ◽  
Shear Test ◽  
Steel Plate ◽  
Maximum Shear Stress ◽  
Deformation Field ◽  
Direct Shear ◽  
Medium Sand ◽  
Dense Sand ◽  
Experimental Process

To study the deformation of soil when interacting with structure, this paper macroscopically analyzes sand deformation field through the direct shear test with sand and steel plate. The test used the invisible semi-model shear device to take photo of experimental process for analysis by digital photography-based deformation measurement(DPDM) technique. The results show that during the process of interaction between dense sand and structure, the influence made by normal stress is more significant than that of compactness. As the normal stress grows, the compactness, the maximum shear stress and the bulk strain of medium sand correspondingly increases. At the beginning of shear, sand far from the plate displays shear shrink while sand close to the plate shows partial shear dilatancy.

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