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.

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 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.

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 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.

scholarly journals Investigating the Effect of Rock Bridge on the Stability of Locked Section Slopes by the Direct Shear Test and Acoustic Emission Technique

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 638 ◽  
Author(s):  
Qifeng Guo ◽  
Jiliang Pan ◽  
Meifeng Cai ◽  
Ying Zhang
Keyword(s):  
Acoustic Emission ◽  
Shear Strength ◽  
Normal Stress ◽  
Direct Shear Test ◽  
Shear Test ◽  
Rock Slope ◽  
Direct Shear ◽  
Acoustic Emission Technique ◽  
Rock Bridge ◽  
The Stability

As a portion of intact rock separating joint surfaces, rock bridge plays a significant role in the stability of rock slopes. This paper aims to investigate the effect of different rock bridges on the mechanical properties and failure mode of rock slope by means of the direct shear test and acoustic emission technique. Field conditions were simulated in direct shear tests which were carried out on specimens with rock bridges at different continuity rates, normal stress, arrangements, and joint angles. Experimental results indicate that the strength of specimens is controlled by the rock bridge and the structural plane. The rock bridge contributes to the strength of the specimen, while the through plane weakens the strength of the specimen. The increase of normal stress can weaken the stress concentration near the tip of the rock bridge and improve the shear resistance of the specimen. The different arrangement of rock bridge has little effect on the normal displacement of the specimen, and has a great influence on the shear strength. The shear capacity of the specimen is related to the angle of the crack, and the angle of the crack is approximately proportional to the peak shear strength. For the specimens with different joint occurrence, the mode of crack propagation at the initial stage is basically the same, and the specimen is finally damaged due to the generation of through cracks in the core area of rock bridge. The instantaneous release of the huge energy generated during the experiment along the shear direction is the root cause of the sudden failure of the rock bridge. The formation, aggregation, and transfixion process of rock bridge is of concern and has been experimentally investigated in this paper for the prevention and control of the locked section rock slope with sudden disasters.

scholarly journals Mohr-Coulomb Failure Condition and the Direct Shear Test Revisited

10.14311/630 ◽  
2004 ◽  
Vol 44 (5-6) ◽  
Author(s):  
P. Řeřicha
Keyword(s):  
Normal Stress ◽  
Failure Criterion ◽  
Direct Shear Test ◽  
Shear Test ◽  
Direct Shear ◽  
Failure Condition ◽  
Critical Plane ◽  
Coulomb Failure ◽  
Extreme Property ◽  
Coulomb Failure Criterion

An alternative critical plane orientation is proposed in the Mohr-Coulomb failure criterion for soils with an extreme property. Parameter identification from the direct shear test is extended to incude the lateral normal stress. 

Evaluation of the Geo-Mechanical Parameters of the Interface between Asphalt Concrete and Sand with Applying Direct Shear Test and Numerical Modeling

2012 ◽  
Vol 587 ◽  
pp. 116-121 ◽  
Author(s):  
Milad Tajdini ◽  
Ali Rostami ◽  
Mohammad M. Karimi ◽  
Hasan Taherkhani
Keyword(s):  
Normal Stress ◽  
Asphalt Concrete ◽  
Direct Shear Test ◽  
Shear Test ◽  
Back Analysis ◽  
Shear Stiffness ◽  
Direct Shear ◽  
Asphaltic Concrete ◽  
Embankment Dams ◽  
Constitutive Parameters

Asphaltic concrete has been used as waterproofing core in embankment dams, since 1948. In this application, the asphaltic core is surrounded by granular filter materials. The interaction of the asphaltic concrete and the granular materials has not been sufficiently investigated. In this paper the mechanical behavior of the interface between a natural smooth sand filter and asphaltic concrete at different levels of normal stresses and a constant shear strain rate has been studied. Small scale direct shear test has been conducted in this study, in which the shear surface is considered as the interface. Asphalt concrete specimens used in the shear test were cut in square shape (10×10×2.5 cm) from cylindrical specimen compacted by modified marshal compaction method. According to the direct shear test the interface constitutive parameters (cohesion, friction angle and shear stiffness) have been obtained. Using the parameters obtained from the direct shear tests, the numerical model of the test by applying FLAC3D Finite Difference software has been made, for which the Mohr-Coulomb constitutive parameters of the asphalt concrete have been obtained from back analysis using ABAQUS Finite Element software according to the conducted Marshal Test results on the asphalt. Utilizing the obtained parameters for both asphalt and interface, the normal stiffness of the interface has been extracted by back analysis with applying FLAC3D. It is shown that the shear stiffness and shear yield strength of the interface between sand and asphalt concrete, and the normal stiffness of the interface increase with increasing the normal stress level since driving direct shear test. The results of this study can help solving numerical problems of the interaction of asphaltic core and surrounding soil with considering more precise interface constitutive value, especially in the embankment dams with asphaltic core, which normal stress distribution on the asphaltic core varies through the different depths in the dam due to the hydrostatic pressure.

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