Microscopic Analysis of Sand Shear Band in Direct Shear Test Based on Particle Flow Theory

2012 ◽  
Vol 170-173 ◽  
pp. 83-87
Author(s):  
Yang Liu ◽  
Jie Hu ◽  
Shun Chuan Wu
Keyword(s):  
Shear Band ◽  
Direct Shear Test ◽  
Shear Test ◽  
Displacement Vector ◽  
Particle Diameter ◽  
Average Particle ◽  
Direct Shear ◽  
Particle Rotation ◽  
Principal Stresses ◽  
Shear Process

In order to analyze the microscopic shear mechanics behavior of sands, a numerical simulation is carried out in sand direct shear test with commercial DEM software PFC2D. By compiling FISH function, PFC2D is able to visualize principal stresses and their inclination inside the sample. In the simulation, particle rotation gradient and particle displacement vector are observed to analyze the microscopic formation mechanism of shear band. The strain and deformation is concentrated in a band whose thickness is about 10 times of average particle diameter and the band is close to the shear plane. The porosity ratio in shear band is higher than other parts of the sample with shear process.

scholarly journals Influence of Maximum Particle Diameter on the Mechanical Behavior of Soil-Rock Mixtures

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Zhuoling He ◽  
Junyun Zhang ◽  
Tao Sun
Keyword(s):  
Shear Strength ◽  
Large Scale ◽  
Direct Shear Test ◽  
Shear Test ◽  
Particle Diameter ◽  
Size Difference ◽  
Direct Shear ◽  
Fine Grained ◽  
Fine Grained Soil ◽  
Maximum Particle

With the steady development of the development of the western region in China, the construction of mountain highways has developed rapidly, and the soil-rock mixed filler, as an excellent filler, is widely used in the subgrade filling of mountain highways. Unlike ordinary fine-grained soil, the source of the soil-rock mixtures (S-RMs) is not unique, and the particle size difference is large and the water content is not uniform, resulting in very complicated mechanical properties. But the current highway embankment codes are still mainly established on the fine-grained soil. It is not fully applicable to soil-rock filled embankment. Based on soil-rock filled embankment engineering practice, this research uses a large-scale direct shear test to research the mechanical characteristics of the S-RMs with different maximum particle diameters. According to the large-scale direct shear test of S-RMs with different maximum particle diameters, the shear displacement vs shear stress curve, shear dilation, and strength characteristics with maximum particle diameter were analyzed. Results demonstrate that whether secondary hardening occurs mainly depends on the normal stress and the maximum particle diameter of the filler. At different maximum particle diameters, the horizontal displacement vs vertical displacement curves of the S-RMs can be roughly divided into continuous shearing and beginning of shearing and quick dilation. And the shear strength increases with the increase of the maximum particle diameter. Moreover, the cohesion decreases first and then increases with the increase of the maximum particle diameter, and the internal friction angle increases with the increase of the maximum particle diameter. Therefore, some RBs with large particle diameter added to filler can effectively improve the shear strength of the S-RMs, which may be valuable for realistic engineering.

Analysis of sand – woven geotextile interface shear behavior using discrete element method (DEM)

2020 ◽  
Vol 57 (3) ◽  
pp. 433-447 ◽  
Author(s):  
Shi-Jin Feng ◽  
Jie-Ni Chen ◽  
Hong-Xin Chen ◽  
Xin Liu ◽  
T. Zhao ◽  
...  
Keyword(s):  
Shear Band ◽  
Discrete Element Method ◽  
Coordination Number ◽  
Direct Shear Test ◽  
Shear Test ◽  
Discrete Element ◽  
Sliding Contact ◽  
Direct Shear ◽  
Interface Shear ◽  
Normal Anisotropy

The interaction between soil and geotextile is essential for the performance of reinforced soil. This study reveals the microscopic mechanism of interface shear between sand and geotextile based on the discrete element method (DEM). The surface characteristics of geotextile are simulated by overlapped particles. The micromechanical parameters of sand, geotextile, and interface are calibrated effectively using laboratory test results. Three types of shear tests on the sand–geotextile interface are simulated; namely, interface direct shear test (IDST), double-sided interface shear test (D_IST), and interface direct shear test with periodic boundary (PBST). For IDST, the results show that the thickness of shear band is 2.4∼3.0 times the average particle diameter (D50); the contact force, percentage of sliding contact, and contact normal anisotropy inside the shear band are larger than those outside the shear band, whereas the coordination number is smaller inside the shear band. The mechanical response of D_IST is similar to that of IDST. However, D_IST has a shear band thickness of 3.0D50, and greater coordination number, percentage of sliding contact, and contact normal anisotropy. The results of PBST indicate that the peak stress and the shear band no longer appear without boundary constraint and the contact distribution is uniform.

scholarly journals Experimental Study on Mesoscopic Shear Behavior of Calcareous Sand Material with Digital Imaging Approach

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Jianhua Shen ◽  
Xing Wang ◽  
Wenbai Liu ◽  
Poyu Zhang ◽  
Changqi Zhu ◽  
...  
Keyword(s):  
Shear Band ◽  
Normal Stress ◽  
Direct Shear ◽  
Particle Rotation ◽  
Calcareous Sand ◽  
Maximum Shear Strain ◽  
Lower Shear ◽  
Analysis Technique ◽  
Shear Process ◽  
Movement Mechanism

The study of the mesostructure of soil under loading is the basis for understanding its macromechanical properties and for establishing its constitutive model. In this study, a series of shear tests was performed on dry calcareous sand under constant normal stress by a modified direct shear apparatus. Digital images of the sample at different shear stages are obtained. The mesostructural parameters of the sample are then extracted and analyzed using an image analysis technique. The results show that the shear-band is located at the junction of the upper and lower shear boxes with a thickness of 0.79–1.59 mm. During shearing, the position of the maximum shear strain incremently shifted to the junctions between the two shear boxes. The azimuths of the particles prior to the test distribute symmetrically on both sides of 90°. After the test, the azimuths of the particles are mainly obtuse angles (150–180°) and the long axis of the particles generally points in the opposite direction from the shear-band. The sand particles undergo four stages: random arrangement during initial sample preparation, compaction under normal stress, particle rotation during shearing, and ordered alignment after shearing. The test results help to reveal the movement mechanism of calcareous sand at the mesoscopic level during the direct shear process.

scholarly journals Influence of Structural Plane Microscopic Parameters on Direct Shear Strength

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Yanhui Cheng ◽  
Weijun Yang ◽  
Dongliang He
Keyword(s):  
Particle Size ◽  
Shear Strength ◽  
Internal Friction ◽  
Direct Shear Test ◽  
Shear Test ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Direct Shear ◽  
Stiffness Ratio ◽  
Structural Plane

Structural plane is a key factor in controlling the stability of rock mass engineering. To study the influence of structural plane microscopic parameters on direct shear strength, this paper established the direct shear mechanical model of the structural plane by using the discrete element code PFC2D. From the mesoscopic perspective, the research on the direct shear test for structural plane has been conducted. The bonding strength and friction coefficient of the structural plane are investigated, and the effect of mesoscopic parameters on the shear mechanical behavior of the structural plane has been analyzed. The results show that the internal friction angle φ of the structural plane decreases with the increase of particle contact stiffness ratio. However, the change range of cohesion is small. The internal friction angle decreases first and then increases with the increase of parallel bond stiffness ratio. The influence of particle contact modulus EC on cohesion c is relatively small. The internal friction angle obtained by the direct shear test is larger than that obtained by the triaxial compression test. Parallel bond elastic modulus has a stronger impact on friction angle φ than that on cohesion c. Under the same normal stress conditions, the shear strength of the specimens increases with particle size. The shear strength of the specimen gradually decreases with the increase of the particle size ratio.

Soil Shear Strength Characteristic in Slope Disintegration Area

2013 ◽  
Vol 353-356 ◽  
pp. 735-739
Author(s):  
Xiao Ming Zhang ◽  
Shu Wen Ding ◽  
Shuang Xi Li
Keyword(s):  
Shear Strength ◽  
Direct Shear Test ◽  
Shear Test ◽  
Clay Content ◽  
Scientific Basis ◽  
Soil Mechanic ◽  
Direct Shear ◽  
Soil Cohesion ◽  
Soil Shear Strength ◽  
The Relationship

Development of slope disintegration is close to soil mechanic characteristics such as shear strength indices. Soil grain diameter and water content were tested. Soil direct shear test was conducted to analyze the relationship between shear strength indices and the influencing factors. The experimental data indicate that clay content and the range affect soil cohesion value and the scope. Soil cohesion increases with bulk density before 1.6g/cm3. But it decreases when the bulk after that. The results could provide a scientific basis for control of slope disintegration.

Bionic Concave Pit-Like Metal Surface and Soil Direct Shear Test

2012 ◽  
Vol 569 ◽  
pp. 451-454 ◽  
Author(s):  
Ya Ming Tang ◽  
Yang Tian
Keyword(s):  
Metal Surface ◽  
Shear Force ◽  
Smooth Surface ◽  
Direct Shear Test ◽  
Shear Test ◽  
Shear Displacement ◽  
Direct Shear ◽  
Typical Soil

In order to test the reducing adhesion and resistance effect of bionic metal non-smooth surface, the direct shear test is experimented on a kind of bionic dredging tools with typical soil and bionic concave pit-like metal surface.The relation of shear force and shear displacement on a certain pressure is presented. The result will help to design the structure of cutting soil tools’ surfaces with less adhesion and resistance.

Experimental investigation on concrete subjected to direct shear test

2021 ◽  
Author(s):  
P.R. Kalyana Chakravarthy ◽  
R. Rakesh ◽  
T. Kiran ◽  
S. Sivaganesan ◽  
A. Parthiban
Keyword(s):  
Experimental Investigation ◽  
Direct Shear Test ◽  
Shear Test ◽  
Direct Shear
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