Shear strength of a pyroclastic unsaturated soil from suction-controlled direct shear tests

2010 ◽  
pp. 347-352 ◽  
Author(s):  
R Papa ◽  
M Nicotera
Keyword(s):  
Shear Strength ◽  
Unsaturated Soil ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests

scholarly journals Direct Shear Test of Unsaturated Soil

2017 ◽  
Vol 21 (4) ◽  
pp. 183-188
Author(s):  
Peng He ◽  
Liuying Sun ◽  
Zhen Wang
Keyword(s):  
Shear Strength ◽  
Unsaturated Soil ◽  
Direct Shear Test ◽  
Shear Test ◽  
Test Scheme ◽  
Direct Shear ◽  
Shear Strength Parameters ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Good Agreement

The present study focuses on some tentative laboratory tests using a newly-constructed modified direct shear test apparatus. The single-stage and multistage direct shear tests were performed to determine the shear rate and test scheme of unsaturated shear test. Shear strength parameters of unsaturated soil in different conditions are obtained and the tests indicate good agreement with typical theories of unsaturated soil, the nonlinear matric suction failure envelope is determined. Some shear strength equations are also fitted through the experimental results. 

scholarly journals Using Post-Harvest Waste to Improve Shearing Behaviour of Loess and Its Validation by Multiscale Direct Shear Tests

2019 ◽  
Vol 9 (23) ◽  
pp. 5206 ◽  
Author(s):  
Wen-Chieh Cheng ◽  
Zhong-Fei Xue ◽  
Lin Wang ◽  
Jian Xu
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Strain Hardening ◽  
Gradual Increase ◽  
Small Scale ◽  
Optimal Dosage ◽  
Direct Shear ◽  
Shear Tests ◽  
Post Harvest ◽  
Direct Shear Tests

Loess and PHW (post-harvest waste) are easily accessible in the Chinese Loess Plateau and have been widely applied to construction of residential houses that have been inhabited for decades under the effect of freeze-thaw cycles. Although many researchers have recognised that the addition of fibers to loess soil is effective in preventing soil erosion and stabilising slopes, a consensus on this claim has not been reached yet. This study investigates the shearing behaviour of the loess-PHW mixture using small-scale and large-scale direct shear (SSDS and LSDS) tests. Four typical shear stress versus horizontal displacement curves from the multiscale direct shear tests are recognised where one is featured with strain-softening shape and the other three with a strain-hardening shape. Two out of the three curves with strain-hardening shape show a gradual increase in the shear stress at additional and larger displacements, respectively, in which some factor starts to have an influence on the shearing behaviour. Comparisons of the shear strength measured in SSDS and LSDS are made, indicating that there are differences between SSDS and LSDS. The effect of PHW addition on shear strength is assessed in order to determine the optimal dosage. The improvement of shear strength is attributed to the effect of particle inter-locking, resulting from the addition of PHW to loess specimens, and takes effect as the water content surpassed a threshold, i.e., >14%, that facilitates particle rearrangement. Particle-box interaction behaviour is assessed at the same time, and the findings satisfactorily address the main cause of the gradual increase in shear stress following the curve inflection point. The improved shearing behaviour proves the ability of the loess-PHW mixture to resist the seepage force and consequently stratum erosion.

Shear Strength of Sand–Clay Interfaces Through Large-Scale Direct Shear Tests

2020 ◽  
Vol 45 (5) ◽  
pp. 4343-4357
Author(s):  
Zhong-Liang Zhang ◽  
Zhen-Dong Cui ◽  
Ling-Zi Zhao
Keyword(s):  
Shear Strength ◽  
Large Scale ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests

Shear strength of unsaturated soil interfaces

2009 ◽  
Vol 46 (5) ◽  
pp. 595-606 ◽  
Author(s):  
Tariq B. Hamid ◽  
Gerald A. Miller
Keyword(s):  
Shear Strength ◽  
Unsaturated Soil ◽  
Characteristic Curve ◽  
Matric Suction ◽  
Direct Shear ◽  
Direct Shear Tests ◽  
Strength Failure ◽  
Suction Control ◽  
Failure Envelopes ◽  
Fine Grained Soil

Unsaturated soil interfaces exist where unsaturated soil is in contact with structures such as foundations, retaining walls, and buried pipes. The unsaturated soil interface can be defined as a layer of unsaturated soil through which stresses are transferred from soil to structure and vice versa. In this paper, the shearing behavior of unsaturated soil interfaces is examined using results of interface direct shear tests conducted on a low-plasticity fine-grained soil. A conventional direct shear test device was modified to conduct direct shear interface tests using matric suction control. Further, the results were used to define failure envelopes for unsaturated soil interfaces having smooth and rough counterfaces. Results of this study indicate that matric suction contributes to the peak shear strength of unsaturated interfaces; however, postpeak shear strength did not appear to vary with changes in matric suction. Variations in net normal stress affected both peak and postpeak shear strength. Failure envelopes developed using the soil-water characteristic curve (SWCC) appeared to capture the nonlinear influence of matric suction on shear strength of soil and interfaces.

Effect of fibre content and structure on anisotropic elastic stiffness and shear strength of peat

2012 ◽  
Vol 49 (4) ◽  
pp. 403-415 ◽  
Author(s):  
Michael T. Hendry ◽  
Jitendra S. Sharma ◽  
C. Derek Martin ◽  
S. Lee Barbour
Keyword(s):  
Shear Strength ◽  
Confining Pressure ◽  
Deviatoric Stress ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
A Value ◽  
Frictional Strength ◽  
Fibrous Peat ◽  
Interparticle Friction

This paper presents the results of a laboratory testing program involving consolidated undrained triaxial tests and direct shear tests on remoulded peat, remoulded peat fibre, and Shelby specimens of peat obtained from a field site located in the Edson subdivision of the Canadian National railway in Alberta, Canada. These results were analyzed within the frameworks of elastic behaviour of cross-anisotropic materials and shear strength of fibre-reinforced soil. Shelby specimens were found to be inherently cross-anisotropic, whereas the remoulded peat and peat fibre specimens showed a transition from isotropic to cross-anisotropic with increasing vertical strain and effective confining pressure. The horizontal stiffness of Shelby specimens was found to be 2.6 to 2.9 times their vertical stiffness. The shear strength of intact peat is made up of interparticle friction as well as tension in the peat fibres. A novel procedure for estimating the interparticle frictional strength of fibrous peat from CU triaxial test results is proposed. It involves extrapolating the linear strain-hardening portion of the stress–strain curve to obtain the deviatoric stress at zero axial strain and plotting the deviatoric stress values thus obtained against initial mean effective confining pressure to obtain the frictional strength. Using this procedure, a value of 31° was obtained for the interparticle friction, which compares favourably with a value of 31° obtained from direct shear tests. It is recommended that further studies be undertaken to assess if interparticle frictional strength is an appropriate strength parameter for evaluation of the stability of structures founded on fibrous peat.

Determination of the shear strength parameters of an unsaturated soil using the direct shear test

1988 ◽  
Vol 25 (3) ◽  
pp. 500-510 ◽  
Author(s):  
J. K. M. Gan ◽  
D. G. Fredlund ◽  
H. Rahardjo
Keyword(s):  
Shear Strength ◽  
Unsaturated Soils ◽  
Testing Procedure ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Wide Range ◽  
Practical Engineering ◽  
Direct Shear Apparatus

Multistage direct shear tests have been performed on saturated and unsaturated specimens of a compacted glacial till. A conventional direct shear apparatus was modified in order to use the axis-translation technique for direct shear tests on unsaturated soils. The soil can be subjected to a wide range of matric suctions. The testing procedure and some typical results are presented. Nonlinearity in the failure envelope with respect to matric suction was observed. Suggestions are made as to how best to handle the nonlinearity from a practical engineering standpoint. Key words: shear strength, unsaturated soils, negative pore-water pressures, soil suction, direct shear.

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