scholarly journals Dynamic modulus characteristics of saturated clays under variable confining pressure

2017 ◽  
Vol 54 (5) ◽  
pp. 729-735 ◽  
Author(s):  
Chuan Gu ◽  
Zhiqiang Gu ◽  
Yuanqiang Cai ◽  
Jun Wang ◽  
Daosheng Ling
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Hyperbolic Model ◽  
Cyclic Triaxial Tests ◽  
Cyclic Shear ◽  
Dynamic Loadings ◽  
Actual Field ◽  
Variable Confining Pressure

Dynamic loadings, induced by earthquakes and other causes, will lead to the cyclic variation of both shear stress and normal stress components on the soil elements. A series of cyclic triaxial tests with and without variable confining pressure were carried out to investigate the coupling effects of cyclic shear stress and cyclic normal stress on the normalized shear modulus, G/Gmax, characteristics of saturated clays. Results indicated that both the phase differences and ratios between the cyclic deviatoric stress and cyclic confining pressure exerted a constant and pronounced influence on the G/Gmax, indicating that the G/Gmax properties under combined loadings will be more representative of actual field conditions than from single-loading conditions. A modified hyperbolic model considering the effects of cyclic confining pressure was further proposed.

DEGRADATION EFFECT OF SEAWATER ON THE LONG-TERM DYNAMIC BEHAVIOR OF ARTIFICIALLY CEMENTED SAND

2013 ◽  
Vol 07 (04) ◽  
pp. 1350031 ◽  
Author(s):  
BO LI ◽  
YUANQIANG CAI ◽  
XIANGWU ZENG ◽  
LINYOU PAN
Keyword(s):  
Shear Modulus ◽  
Dynamic Behavior ◽  
Tap Water ◽  
Damping Ratio ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Resonant Column ◽  
Cyclic Triaxial Tests ◽  
Cemented Sand

The dynamic behavior of lightly cemented sand under long-term seawater attack was evaluated in this study. Resonant column and cyclic triaxial tests were employed to investigate the evolution of the shear modulus and damping ratio of cemented sand with respect to soaking period (SP), confining pressure, and cement content (CC). The results of this study show that the cementation of the sand is affected by soaking in seawater to a greater extent than by soaking in tap water. The shear modulus of the cemented sand soaked in seawater was smaller than that of the cemented sand soaked in tap water. The damping ratio increased significantly, as the SP increased and was greater for the cemented sand soaked in seawater than for the cemented sand soaked in tap water. The dynamic behavior of nonhomogenous specimens was examined. Crystallization of salts could be clearly observed and probably explains the evolution of the dynamic behavior of the cemented sand. Finally, the shear modulus was fitted using Rollins' Law [Rollins et al., 1998], which demonstrates that the parameters used in the equation can be reasonably fitted linearly over a range of SPs.

Cyclic shear strength of a loose glacial till

1988 ◽  
Vol 25 (2) ◽  
pp. 401-407
Author(s):  
Guy Lefebvre ◽  
Serge Malenfant
Keyword(s):  
Simple Shear ◽  
Glacial Till ◽  
Silty Sand ◽  
Triaxial Tests ◽  
Test Results ◽  
Shear Tests ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests ◽  
Cyclic Shear ◽  
Testing Procedures

The liquefaction potential of a loose glacial till is assessed by laboratory cyclic tests and by comparison with test results obtained on a clean sand, using the same testing procedures. The laboratory testing program of both soils included cyclic triaxial tests on saturated specimens and constant volume cyclic simple shear tests on dry specimens. The till and the sand exhibited very similar behaviour during cycling and mobilized nearly identical cyclic shear strengths in the triaxial as well as in the simple shear tests. The 28% fines content in the till did not make it more resistant to liquefaction than a clean sand. Key words: liquefaction, sand, silty sand, cyclic simple shear test, cyclic triaxial test.

Liquefaction Testing of Stratified Sands Interlayered with Silt

2012 ◽  
Vol 256-259 ◽  
pp. 116-119 ◽  
Author(s):  
Min Cai Jia ◽  
Bing Ye Wang
Keyword(s):  
Critical Thickness ◽  
Confining Pressure ◽  
Cyclic Behavior ◽  
Triaxial Tests ◽  
Experimental Program ◽  
Cyclic Triaxial Tests ◽  
Hydraulic Fill ◽  
Soil Deposits ◽  
History Of ◽  
Different Thickness

The cyclic behavior of stratified sands interlayered with silt is at present poorly understood, although stratified sands exist for various soil deposits and hydraulic fill, which have a history of liquefaction during earthquakes. The main objective of this research project was to compare the cyclic behavior of stratified and homogeneous sands for various silt contents. A comprehensive experimental program was undertaken in which stain-controlled undrained cyclic triaxial tests for stratified sand samples interlayered with different thickness silt were performed. The silt thickness ranged from 0 to 80mm was considered. The confining pressure in all test series was 100kPa. The results indicate that the thickness of the silt seam sandwiched in the sand samples has a significant influence on the liquefaction resistances of layered sands. In other words, there is a critical thickness of silt seam that the saturated stratified sands have a critical shear strain. This finding justifies applying the laboratory tests results of homogeneously reconstituted samples to the field conditions for the range of variable studied.

scholarly journals Cyclic Loading Test for the Small-Strain Shear Modulus of Saturated Soft Clay and Its Failure Mechanism

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Zhende Zhu ◽  
Cong Zhang ◽  
Jun Wang ◽  
Peng Zhang ◽  
Duan Zhu
Keyword(s):  
Shear Stress ◽  
Shear Modulus ◽  
Effective Stress ◽  
Soft Clay ◽  
Small Strain ◽  
Triaxial Tests ◽  
Loading Test ◽  
Cyclic Shear ◽  
Small Strain Shear Modulus ◽  
Saturated Soft Clay

Small-strain shear modulus, G max , is a key evaluation index to study the dynamic characteristics of soil in geotechnical engineering. It is widely adopted to evaluate the stiffness of soft soil in soil dynamic engineering. In this paper, the cyclic triaxial tests and resonance column tests were carried out to explore the variation of G max of soft clay with respect to various confining stresses, cyclic shear stress ratios, pore pressures, and effective stress paths. Test results indicated that the effective stress decreased gradually with the increase of the cycle shear stress ratio. The failure points were mainly concentrated in a rectangular area, defined by the normalized effective stress from 0.56 to 0.64 and the normalized shear modulus from 0.72 to 0.78. Additionally, a short pause caused a small increase of 1-2% in G max as well as pore pressure. This study demonstrates that G max can be effectively used to characterize the failure of saturated soft clay in a more intuitive and convenient way, compared to the commonly used strain failure standards.

Experimental Study on Dynamic Characteristics of Tailings

2014 ◽  
Vol 580-583 ◽  
pp. 455-459
Author(s):  
Jian Bin Zhao ◽  
Ying Chun Ji ◽  
Xiao Liu ◽  
Di Li
Keyword(s):  
Elastic Modulus ◽  
Dynamic Characteristics ◽  
Damping Ratio ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Coarse Grain ◽  
Test Results ◽  
Cyclic Triaxial Tests ◽  
Copper Tailings ◽  
Fine Grain

In this paper, the dynamic characteristics for three different kinds of copper tailings are studied through a series of cyclic triaxial tests. It is found that under confining pressure 200 and 300 kPa, elastic modulus raises with the increasement of coarse grain content to a certain degree and then declines, and the maximum elastic modulus corresponds to good gradation. While, as for confining pressure 100 kPa, elastic modulus raises with the increasement of fine grain content. It is also found that elastic modulus raises with the increasement of confning pressure. And, damping ratio raises with the increasement of shear strain and finally to a stable value. Finally, the fitting Gd/Gdmax~ curve for three kinds of tailings shows the reasonableness of test results.

scholarly journals Undrained Cyclic Shear Strength and Residual Shear Strain of Saturated Sand by Cyclic Triaxial Tests

1991 ◽  
Vol 31 (3) ◽  
pp. 60-76 ◽  
Author(s):  
Masayuki Hyodo ◽  
Hidekazu Murata ◽  
Noriyuki Yasufuku ◽  
Teruhisa Fujii
Keyword(s):  
Shear Strength ◽  
Shear Strain ◽  
Triaxial Tests ◽  
Saturated Sand ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests ◽  
Cyclic Shear

Effect of variable confining pressure on cyclic behaviour of granular soil under triaxial tests

2017 ◽  
Vol 54 (6) ◽  
pp. 768-777 ◽  
Author(s):  
Qi Sun ◽  
Yuanqiang Cai ◽  
Jian Chu ◽  
Quanyang Dong ◽  
Jun Wang
Keyword(s):  
Initial Stress ◽  
Stress Ratio ◽  
Permanent Deformation ◽  
Confining Pressure ◽  
Stress Path ◽  
Average Stress ◽  
Triaxial Tests ◽  
Cyclic Behaviour ◽  
Different Strains ◽  
Variable Confining Pressure

Previous studies were performed to use combined cyclic deviatoric stress and confining pressure to simulate cyclic vertical and horizontal normal stresses under traffic loading. The effect of variable confining pressure (VCP) on the permanent deformation of soils was investigated. However, some studies concluded VCP could promote the development of permanent deformation compared to the tests with constant confining pressure (CCP), while others drew the opposite conclusions. In this study, three types of CCP and VCP tests with identical maximum stress, identical average stress, and identical initial stress were conducted. Test results showed VCP tests accumulated more permanent strains when CCP and VCP tests had identical maximum or average stress, and the permanent strains increased with the decrease in the inclinations of stress paths, while similar permanent strains were generated when CCP and VCP tests had identical initial stress. In addition, larger permanent strains were generated with the increase in stress ratio or length of stress path in both CCP and VCP tests. Considering that different strains were cumulated in CCP and VCP tests with the same stress ratio, it is recommended that both stress ratio and length of stress path be considered to assess the permanent deformation.

The Strength and Stress-Strain Characteristics of Oakdale Coal under Triaxial Compression

1960 ◽  
Vol 97 (5) ◽  
pp. 422-435 ◽  
Author(s):  
D. W. Hobbs
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Elastic Strain ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Laboratory Measurements ◽  
Stress Concentrations ◽  
Stress Strain ◽  
Coking Coal ◽  
Local Edge

AbstractLaboratory measurements of the effect of a confining pressure on the strength and stress-strain characteristics of a metallurgical coking coal are described. Several-fold increases in the strength, the Young's modulus and the elastic strain at failure were found as the confining pressure was increased to 5,000 lb./n.2. The results are discussed in relation to various criteria of failure. It was found that failure was represented by Coulomb's equation relating shear stress and normal stress, provided the observed angles of fracture were not influenced by local edge stress concentrations.

Permanent deformation characteristics of saturated sand under cyclic loading

2015 ◽  
Vol 52 (6) ◽  
pp. 795-807 ◽  
Author(s):  
Yuanqiang Cai ◽  
Qi Sun ◽  
Lin Guo ◽  
C. Hsein Juang ◽  
Jun Wang
Keyword(s):  
Shear Stress ◽  
Stress Ratio ◽  
Permanent Deformation ◽  
Confining Pressure ◽  
Stress Path ◽  
Deviatoric Stress ◽  
Loading Path ◽  
Triaxial Tests ◽  
Deformation Characteristics ◽  
Torsional Shear

The loading path involving principal stress rotation (PSR) during shear is an important phenomenon encountered in many field conditions. Typically for traffic loading, both the magnitude and direction of principal stresses may vary with time due to the motion of vehicles, and the stress path can be mimicked by a heart shape in the deviatoric stress space. Conventional triaxial tests are not suitable to recreate this type of stress path in that no torsional shear stress can be applied on the test samples. To overcome this limitation, a series of tests using a hollow cylinder apparatus were conducted on sand to investigate the permanent deformation characteristics under drained conditions with different levels of confining pressure (σc), cyclic vertical stress ratio (CVSR), and cyclic torsional stress ratio (η). The results clearly show an increase in the permanent deformation with η, indicating that the PSR effect on permanent deformation cannot be ignored. Both σc and CVSR were found to also affect permanent deformation, which was more pronounced when PSR was coupled into the test. A five-parameter formulation that accounted for the effect of confining pressure, deviatoric stress, torsional shear stress, and number of loading cycles was subsequently established to analyze the permanent strain. The formulation coefficients were first determined and then used to explain the effects of stress variables on the permanent deformation. Validation studies were performed to address the adequacy of the formulation to predict permanent deformation.

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