scholarly journals Mechanical properties and stress–dilatancy relationships of unsaturated soil under various cyclic loading conditions

2019 ◽  
Vol 15 (7) ◽  
pp. 1799-1813
Author(s):  
Win Tun Tun ◽  
Tomotaka Sato ◽  
Hirotaka Saito ◽  
Yuji Kohgo

AbstractMost studies investigating the effect of cyclic loading on soil properties have been conducted for saturated soils. Embankments such as fill dams, roads and railways are usually constructed by unsaturated geo-materials and retained under unsaturated conditions during their in-service periods. Then when the stabilities of the embankments against dynamic motions such as earthquakes and traffic loads are evaluated, it is necessary to account for the cyclic properties of unsaturated soils. However, there are few studies investigating mechanical properties of unsaturated soils under cyclic loadings. There are two objectives in this paper. One objective is to investigate cyclic properties of an unsaturated silt under various cyclic loading conditions, while the other is to investigate the stress–dilatancy relationships; the relation of plastic strain increment ratio,  − dεvp/dγp, versus stress ratio, q/p′; and to derive the plastic potential function of the unsaturated silt. Cyclic triaxial compression tests under various loading conditions were performed using the unsaturated silt. The material used is an artificial silty soil named DL clay. It was found from the series of the tests that the stiffness of the soil increased with an increase in suction and the number of cyclic loadings. The total volume reductions in the specimens decreased with an increase in suction. When the numbers of cyclic loadings and suction increased, the dilation also increased. Each unique stress–dilatancy relationship could be found in both loading and unloading processes. The relationships were similar to those of saturated soils under cyclic loadings. A unique plastic potential function could also be derived from the stress–dilatancy relationships.

2016 ◽  
Vol 858 ◽  
pp. 91-97
Author(s):  
Jun Hua Xiao ◽  
Wen Qi Zheng

To investigate the macroscopic mechanical properties of undisturbed structural Xiashu loess in the lower reaches of China’s Yangtze River under triaxial compression, and obtain the intrinsic explanations for the macroscopic mechanical properties from the microscopic point of view, in laboratory, triaxial compression tests were carried out, microstructure images of sheared samples were collected by scanning electron microscope (SEM), and quantitative parameters of microstructure (mainly about particle or pore size, distribution, and alignment) were extracted by digital image processing technique. Based on the test results, the deviator stress-strain relationships of both undisturbed and remoulded Xiashu loess, the structural strength, and the microstructural evolution mechanism about the formation of shear failure zone of Xiashu loess under triaxial compression were analyzed.


2013 ◽  
Vol 353-356 ◽  
pp. 802-805
Author(s):  
Jian Qing Jiang

Red-sandstone granular soil reinforced with gabion-mesh is a new concept of composite reinforced soil. In order to reveal the mechanical properties of this composite reinforced soil, a series of laboratory triaxial compression tests on specimens reinforced with gabion-mesh were carried out, and 3D discrete element method was introduced to simulate the triaxial tests. The macro stress-strain relation of red-sandstone specimens reinforced with gabion-mesh was reproduced by the 3D discrete element model. The results show that 3D discrete element method is an ideal technique to study the meso-mechanical nature characteristics of gabion-mesh reinforced red-sandstone granular soil.


1994 ◽  
Vol 353 ◽  
Author(s):  
M. Umedera ◽  
A. Fujiwara ◽  
N. Yasufuku ◽  
M. Hyodo ◽  
H. Murata

AbstractA series of triaxial compression tests is being conducted under the drained condition on bentonite and sand mixtures, known as buffer, in saturated and optimum water content states to clarify the mechanical properties of the buffer.It was found that the mechanical properties of bentonite and sand mixtures are strongly influenced by water and bentonite contents: shear strength in a saturated state is less than that in an optimum water content state; shear strength decreases rapidly with increasing bentonite content. Strength properties are much dependent on confining pressure.


Author(s):  
Tingyu Wu ◽  
Jie Han ◽  
Yuanqiang Cai ◽  
Lin Guo ◽  
Jun Wang

Cyclic loading-induced deformation of soil is a common problem in the engineering practice. In the current practice, however, monotonic triaxial tests are more commonly used in the practice, due to the availability of apparatus and ease of operation. Thus, it will be very useful and practical if the monotonic triaxial tests can be used to evaluate the behavior of soil under cyclic loading. This study aims to find an explicit relationship between monotonic and cyclic behavior of saturated soft clay. Six monotonic and nine cyclic triaxial compression tests were conducted on undisturbed saturated soft clay under an undrained condition. The test results showed that the monotonic and cyclic tests shared the same stress-strain surface in a three-dimensional space p^'-q-ε_a. It is also found possible to evaluate the effective stress states of cyclic tests at two specific numbers of cycles, using corresponding monotonic tests. Based on these two findings, a simple procedure was then proposed to predict the peak axial strain for the saturated soft clay under different cyclic loadings based on the monotonic tests and only one cyclic test, which was further verified against more test data from the previous literature.


2000 ◽  
Vol 2000.13 (0) ◽  
pp. 805-806
Author(s):  
Akira KURAKAKE ◽  
Masataka TOKUDA ◽  
Tadashi INABA ◽  
Hiroyuki OHIGASHI ◽  
Yang CHEN

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Huilin Le ◽  
Shaorui Sun ◽  
Feng Zhu ◽  
Haotian Fan

Flaws existing in rock mass are one of the main factors resulting in the instability of rock mass. Epoxy resin is often used to reinforce fractured rock mass. However, few researches focused on mechanical properties of the specimens with a resin-infilled flaw under triaxial compression. Therefore, in this research, epoxy resin was selected as the grouting material, and triaxial compression tests were conducted on the rock-like specimens with a grout-infilled flaw having different geometries. This study draws some new conclusions. The high confining pressure suppresses the generation of tensile cracks, and the failure mode changes from tensile-shear failure to shear failure as the confining pressure increases. Grouting with epoxy resin leads to the improvement of peak strengths of the specimens under triaxial compression. The reinforcement effect of epoxy resin is better for the specimens having a large flaw length and those under a relatively low confining pressure. Grouting with epoxy resin reduces the internal friction angle of the samples but improves their cohesion. This research may provide some useful insights for understanding the mechanical behaviors of grouted rock masses.


Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3618 ◽  
Author(s):  
Longlong Pang ◽  
Yuzhong Yang ◽  
Liyun Wu ◽  
Fei Wang ◽  
Han Meng

The particle size of coal particles is an important factor affecting the physical and mechanical properties of coal. In this study, uniaxial and triaxial compression tests were conducted to investigate the effects of coal particle size on the physical and mechanical properties of briquettes and their impact mechanism using a rock mechanics test-150B servo system (RMT-150B). The results showed that the uniaxial compression strength, elastic modulus and deformation modulus of briquettes increase when particle size is decreased. The deformation characteristics of the briquettes directly prepared by raw tectonic coal were similar to those of coal specimens with a particle size of 0.18–0.25 mm. The cohesion and strength of coal specimens increased when particle size was decreased, and the plastic deformation capacity decreased when particle size was decreased, showing a strong correlation. The f briquette directly prepared by the raw tectonic coal had a strength between that of coal specimens with a particle size of 2–6 mm and those with a particle size of 0.18–0.25 mm. The mechanical properties of briquettes mainly depend on the meshing force between the coal particles. The smaller the particles, the greater the mechanical meshing force. The “floating particles”, generated in the voids between coal particles during the preparation process, are a significant factor affecting the plasticity characteristics. The research results may be used as a basic reference in the study of the mechanical properties of tectonic coal, gas migration and coal and gas outburst mechanisms.


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