Experimental Study on Shear Mechanical Characteristics of Cohesionless Granular Material

2011 ◽  
Vol 90-93 ◽  
pp. 230-233
Author(s):  
Hong Chun Xia ◽  
Guo Qing Zhou ◽  
Ze Chao Du
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Mechanical Characteristics ◽  
Stress Condition ◽  
Fine Sand ◽  
Shear Displacement ◽  
Direct Shear ◽  
Steel Particle ◽  
High Normal Stress ◽  
Fine Gravel

The direct shear mechanical characteristics of gravel, sand and steel particle were studied systematically using DRS-1 high normal stress direct and residual shear apparatus. The results show that the shear mechanical characteristics of gravel, sand and steel particle is different under different normal stress condition. For steel particle, the curves of shear stress-shear displacement present strain softening regardless of the magnitude of normal stress, and the shear displacement corresponding to the peak shear stress increases with the normal stress. Under low normal stress condition, the volume of fine gravel and steel particle expand, but the fine sand contracts at the beginning of direct shear and then contracts. Under high normal stress condition, the volume of steel particle contracts at the beginning of the direct shear and then contracts, but the fine sand and fine gravel contract throughout the direct shear. The particle breakage has significant effect on the shear strength of fine sand and fine gravel. Under the same high normal stress condition, the volume of fine gravel is greater than that of fine sand, which indicates that the fine gravel is easier to be crushed than the fine sand.

Experimental Study on Shear Mechanical Characteristics of Soil-Structure Interface under Different Normal Stress

2011 ◽  
Vol 243-249 ◽  
pp. 2332-2337 ◽  
Author(s):  
Hong Chun Xia ◽  
Guo Qing Zhou ◽  
Ze Chao Du
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Normal Stress ◽  
Soil Structure ◽  
Mechanical Characteristics ◽  
Shear Displacement ◽  
Interface Roughness ◽  
Displacement Curve ◽  
Direct Shear ◽  
High Normal Stress

The direct shear mechanical characteristics of soil-structure interface under different experimental condition were studied systematically using the DRS-1 high normal stress direct and residual shear apparatus. The results show that the normal stress is an important factor which determines the mechanical characteristics of soil-structure interface. The curve of shear stress-shear displacement presents strain softening when the normal stress<3MPa, linear hardening when =3~5MPa and strain hardening when12MPa, separately. At the same time, the volume of the soil expands when <3MPa and contracts when >3MPa. But the volume of the soil expands and contracts simultaneously during the process of direct shear when =3MPa.The roughness of the interface influences not only the shape of the shear stress-shear displacement curve but also the shear strength of the interface. Under same normal stress condition，the shear strength of interface increases with the roughness but the influence degree of interface roughness reduces gradually with the increase of normal stress. The grain breakage degree is different under different normal stress. It increases evidently with the increase of normal stress.

scholarly journals Time-Dependent Response of a Recycled C&D Material-Geotextile Interface under Direct Shear Mode

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3070
Author(s):  
Fernanda Bessa Ferreira ◽  
Paulo M. Pereira ◽  
Castorina Silva Vieira ◽  
Maria de Lurdes Lopes
Keyword(s):  
Shear Stress ◽  
Stress Relaxation ◽  
Shear Displacement ◽  
Time Dependent ◽  
Shear Behaviour ◽  
Displacement Rate ◽  
Shear Mode ◽  
Direct Shear ◽  
Constant Displacement ◽  
Shear Box

Geosynthetic-reinforced soil structures have been used extensively in recent decades due to their significant advantages over more conventional earth retaining structures, including the cost-effectiveness, reduced construction time, and possibility of using locally-available lower quality soils and/or waste materials, such as recycled construction and demolition (C&D) wastes. The time-dependent shear behaviour at the interfaces between the geosynthetic and the backfill is an important factor affecting the overall long-term performance of such structures, and thereby should be properly understood. In this study, an innovative multistage direct shear test procedure is introduced to characterise the time-dependent response of the interface between a high-strength geotextile and a recycled C&D material. After a prescribed shear displacement is reached, the shear box is kept stationary for a specific period of time, after which the test proceeds again, at a constant displacement rate, until the peak and large-displacement shear strengths are mobilised. The shear stress-shear displacement curves from the proposed multistage tests exhibited a progressive decrease in shear stress with time (stress relaxation) during the period in which the shear box was restrained from any movement, which was more pronounced under lower normal stress values. Regardless of the prior interface shear displacement and duration of the stress relaxation stage, the peak and residual shear strength parameters of the C&D material-geotextile interface remained similar to those obtained from the conventional (benchmark) tests carried out under constant displacement rate.

scholarly journals Determining the Shear Strength Properties of a Soil-geogrid Interface Using a Large-scale Direct Shear Test Apparatus

2020 ◽  
Author(s):  
Jakub Stacho ◽  
Monika Sulovska ◽  
Ivan Slavik
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Large Scale ◽  
Direct Shear Test ◽  
Shear Test ◽  
Strength Properties ◽  
Coarse Grained ◽  
Direct Shear ◽  
Test Apparatus ◽  
Fine Gravel

The paper deals with the laboratory testing of coarse-grained soils that are reinforced using a geogrid. The shear strength properties were determined using a large-scale direct shear test apparatus. The tests were executed on original as well as on reinforced soil, when the geogrid was placed on a sliding surface, which permitted determining the shear strength properties of the soil-geogrid interface. The aim of the tests was to determine the interface shear strength coefficient α, which represents the ratio of the shear strength of the soil-geogrid interface to the unreinforced soil. The tests were executed on 3 samples of coarse-grained materials, i.e., poorly graded sand, poorly graded fine gravel and poorly graded medium gravel. Two types of geogrids were tested, i.e., a woven polyester geogrid and a stiff polypropylene geogrid. The results of the laboratory tests on the medium gravel showed that the reduction coefficient α reached higher values in the case of the stiff polypropylene geogrid. In the cases of the fine gravel and sand, the values of the interface coefficient α were similar to each other. The shear strength of the interface was reduced or was similar to the shear strength of unreinforced soil in a peak shear stress state, but significantly increased with horizontal deformations, especially for the fine gravel and sand. The largest value of the coefficient α was measured in the critical shear stress state. Based on the results of the testing, a correlation which allows for determining the optimal grain size distribution was obtained.

scholarly journals The effect of particle shape on the deformation and stress reduction of a gravel soil due to wetting

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Reza Mahinroosta ◽  
Vahid Oshtaghi
Keyword(s):  
Particle Size ◽  
Shear Stress ◽  
Particle Size Distribution ◽  
Normal Stress ◽  
Size Distribution ◽  
Stress Reduction ◽  
Particle Shape ◽  
Particle Breakage ◽  
Direct Shear ◽  
Particle Shapes

AbstractThis paper investigates the effect of particle shape on the stress reduction and collapse deformation of gravelly soil using a medium-scale direct shear test apparatus under different relative densities, normal stress, and shear stress levels. A new method based on the Micro-Deval test was introduced to produce sub-angular particles from angular particles. Therefore, two series of soil specimens were obtained with the same rock origin, particle size distribution, and relative density but different particle shapes. In addition to traditional direct shear tests on dry and wet specimens, a specific test procedure was applied to explore the stress reduction and collapse of soil specimens due to wetting. The results of the tests, including shear stress–shear displacement and vertical displacement-shear displacement, were compared. The results showed that the stress reduction and settlement due to wetting increased with vertical and shear stress levels in both types of particle shapes, with higher values in angular particle shapes. The particle breakage of the soil specimens was also studied quantitatively using the change in the particle size distribution before and after the test. It was shown that the wetting of the samples had more impact on the particle breakage in angular gravel than sub-angular gravel, which increased linearly with the normal stress.

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.

Curved Box-Girders with Corrugated Steel Webs under Torsion Loading

2011 ◽  
Vol 105-107 ◽  
pp. 837-843
Author(s):  
Bing Wen Yang ◽  
Jian Dong Zhang ◽  
Shui Wan
Keyword(s):  
Differential Equation ◽  
Shear Stress ◽  
Normal Stress ◽  
Mechanical Characteristics ◽  
Orthotropic Plates ◽  
Box Girders ◽  
Corrugated Webs ◽  
Curved Girders

It is known that coupled bending and torsional effect is a distinct characteristic of curved girders. According to mechanical characteristics of box girders with corrugated steel webs and theory of box girders, warping normal stress of box girders with corrugated steel webs caused by Torsion Loading is studied. On the basis of second theory of Wu, restrained torsion differential equation of box-girders with corrugated steel webs is proposed. Corrugated webs are assumed as orthotropic plates. Constraint torsional normal stress and shear stress are deduced using Initial parameters method. The results demonstrate that the method is more accurate compared with conventional ones, and it is connected with existing bridge calculation theory. The method is then a practical one in this respect.

scholarly journals Numerical Simulation of the Shear Behaviour of Cement Grout

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Jianhang Chen ◽  
Fan Zhang ◽  
Hongbao Zhao ◽  
Junwen Zhang
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Stress Distribution ◽  
Normal Stress ◽  
Shear Failure ◽  
Cement Grout ◽  
Shear Stress Distribution ◽  
Shear Behaviour ◽  
Direct Shear ◽  
Failure Plane

Cement grout is widely used in civil engineering and mining engineering. The shear behaviour of the cement grout plays an important role in determining the stability of the systems. To better understand the shear behaviour of the cement grout, numerical direct shear tests were conducted. Cylindrical cement grout samples with two different strengths were created and simulated. The numerical results were compared and validated with experimental results. It was found that, in the direct shear process, although the applied normal stress was constant, the normal stress on the contacted shear failure plane was variable. Before the shear strength point, the normal stress increased slightly. Then, it decreased gradually. Moreover, there was a nonuniform distribution of the normal stress on the contacted shear failure plane. This nonuniform distribution was more apparent when the shear displacement reached the shear strength point. Additionally, there was a shear stress distribution on the contacted shear failure plane. However, at the beginning of the direct shear test, the relative difference of the shear stresses was quite small. In this stage, the shear stress distribution can be assumed uniform on the contacted shear failure plane. However, once the shear displacement increased to around the shear strength point, the relative difference of the shear stresses was obvious. In this stage, there was an apparent nonuniform shear stress distribution on the contacted shear failure plane.

scholarly journals Direct Shear Experimental Study on the Mobilized Dilation Behavior of Granite in Alxa Candidate Area for High-Level Radioactive Waste Disposal

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 122
Author(s):  
Cheng Cheng ◽  
Xiao Li ◽  
Nengxiong Xu ◽  
Bo Zheng
Keyword(s):  
Shear Stress ◽  
Radioactive Waste ◽  
Normal Stress ◽  
Waste Disposal ◽  
Radioactive Waste Disposal ◽  
Direct Shear ◽  
Dilation Angle ◽  
Deformation Behaviors ◽  
High Level ◽  
Granite Samples

Dilation behavior is of great importance for reasonable modeling of the stability of the host rock of the repository for high-level radioactive waste disposal. It is a suitable method for carrying out direct shear experiments to analyze the dilation behavior of rock with well understood physical meanings. Based on a series of direct shear experiments on granite samples from the Alxa candidate area under different normal stresses, the shear stress‒shear strain and shear stress‒normal strain relations have been studied in detail. Five typical stages have been divided associated with the fracturing process and deformation behaviors of the granite samples during the experimental process, and the method to determine the typical stress thresholds has been proposed. It has also been found that the increasing normal stress may reduce the maximum dilation angle, and when the normal stress is relatively lower, the negative dilation angle may occur during the post-peak stage. According to the data collected from the direct shear tests, an empirical model of the mobilized dilation angle dependent on normal stress and plastic shear strain is proposed. This mobilized dilation angle has clear physical meanings and can be used in plastic constitutive models of the host rock of the repository, and this analysis can also be put forward to other types of geomechanical problems, including the deformation behaviors related to landslide, earthquake, and so on.

scholarly journals Effect of Particle Shape on the Deformation and Stress Reduction of a Gravel Soil Due to Wetting

2021 ◽  
Author(s):  
Reza Mahinroosta ◽  
Vahid Oshtaghi
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Stress Reduction ◽  
Particle Shape ◽  
Shear Loading ◽  
Shear Stresses ◽  
Direct Shear ◽  
Gravelly Soil ◽  
Particle Shapes ◽  
Angular Particles

Abstract In this paper, the effect of particle shape is investigated on the stress reduction and collapse deformation of gravelly soil using medium-scale direct shear test apparatus under different relative densities, normal stress, and shear stress levels. The Micro-Deval test was used to produce sub-angular particles from angular particles with continuous smoothening of the corners of the particles. Two series of soil specimens were obtained with the same rock type, particle size distribution, and relative density but different particle shapes. In addition to traditional direct shear tests on dry and wet specimens, a specific test procedure was applied to explore the stress reduction and collapse of soil specimens due to wetting. For instance, dry soil specimens under several normal pressure were subjected to shear loading while inundated at several levels of shear stresses. The results showed that the stress reduction and settlement due to wetting increased with vertical and shear stress level in both types of particle shapes, with higher values in angular particle shapes. The wetting of the samples had more impact on the particle breakage in angular gravel than sub-angular gravel, which increased linearly with the normal stress.

scholarly journals Ice At Melting Point Sliding Over A Pebble Slab–A Film

1979 ◽  
Vol 23 (89) ◽  
pp. 411
Author(s):  
W. F. Budd ◽  
N. A. Blundy
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Graphite Particle ◽  
Time Lapse ◽  
Shear Stresses ◽  
Cold Room ◽  
Set Up ◽  
High Normal Stress ◽  
Dial Gauge ◽  
Movie Camera

Abstract A time-lapse movie technique has been developed to study processes taking place near the interface when ice under high normal stress slides over a rough slab for shear stresses and sliding velocities comparable to those of real glaciers. The “sledge rig” described by Budd and others (1979) was set up with one of the strips of ice (160 mm long and 23 mm wide) close to the edge of the pebble slab on which it rested. The normal stress was applied by loading the rig with lead to 5 bars. The shear stress was applied by a direct load on a cable over a pulley while the rig rested on the slab on a strong table. Shear stresses in the range 1 to 2 bars were used giving velocities from about 50 to 500 m a–1. Beyond 2 bars it was found that acceleration would set in, so this was avoided. A time-lapse movie camera was set up beside the rig to focus first on the whole configuration and then on the ice and interface as a close-up. A flash light was set up behind the rig to shine through the ice strip. A scale rule was placed along the slab under the ice strip. A dial-gauge micrometer was also used to monitor displacement. A time-lapse frequency of about 1 frame per 8 s was found to give a suitable speed. An automatic control triggered the camera and flash and also recorded the number of frames. A number of different markings were tried on the ice to indicate the relative ice deformation. Small graphite particle tracers were found the most successful. A number of runs have been filmed showing the ice sliding speed increasing with increasing shear stress. The tests were carried out in a cold room at a temperature close to 0°C. Copies of the film can be made available at cost. The authors were greatly assisted by Mr David Gardner of the Department of Educational Technology of Melbourne University by the provision of the filming equipment and general support for the operation.

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