Liquefaction assessment by the unit energy concept through centrifuge and torsional shear tests

2007 ◽  
Vol 44 (11) ◽  
pp. 1286-1297 ◽  
Author(s):  
Hesham M. Dief ◽  
J. Ludwig Figueroa
Keyword(s):  
Unit Volume ◽  
Site Response ◽  
Confining Pressure ◽  
Cohesionless Soils ◽  
Shear Tests ◽  
Liquefaction Susceptibility ◽  
Torsional Shear ◽  
Energy Concept ◽  
Unit Energy ◽  
Different Grain Size

The fundamentals of the energy concept to assess the liquefaction potential of cohesionless soils have been formulated in recent years. To examine the validity of this procedure, a series of centrifuge liquefaction tests were carried out using the same soils that were tested previously as part of extensive research conducted on the subject at Case Western Reserve University. A total of 30 liquefaction tests at accelerations of 50g and 60g  were conducted on scaled pore fluid saturated models, prepared in a laminar box, representing a prototype soil deposit. The influence of relative density and effective confining pressure, as well as the effect of different grain size distribution on the energy per unit volume required for liquefaction, is studied. Generalized relationships were obtained by performing regression analyses between the energy per unit volume at the onset of liquefaction and liquefaction affecting parameters. These equations are compared with similar ones that were developed previously using torsional shear tests. A rational procedure to determine site response to earthquake loading and liquefaction susceptibility of a soil deposit is verified.

Experimental Research on Dynamic Poisson’s Ratio of Silty Clay

2010 ◽  
Vol 168-170 ◽  
pp. 286-292
Author(s):  
Hua Pan ◽  
Guo Xing Chen ◽  
Tian Sun
Keyword(s):  
Shear Strain ◽  
Poisson’S Ratio ◽  
Stress Ratio ◽  
Confining Pressure ◽  
Poisson's Ratio ◽  
Cyclic Loads ◽  
Silty Clay ◽  
Shear Tests ◽  
Torsional Shear ◽  
Hollow Cylinder Apparatus

Cyclic triaxial and cyclic torsional shear tests were performed on undisturbed marine silty clay by the hollow cylinder apparatus, and the Young’s modulus and shear modulus were obtained respectively. Furthermore, the influence of effective confining pressure and stress ratio on dynamic Poisson’s ratio was investigated on this basis. It was found that the dynamic Poisson’s ratio increases with generalized shear strain, but decreases with increasing effective confining pressure and stress ratio. The effect of effective confining pressure and stress ratio on dynamic Poisson’s ratio was weakened as the generalized shear strain was increasing. The dynamic Poisson’s ratio was about 0.48 when the Poisson’s ratio was increased to 1.8E-2 or so, and the test was terminated. There was no shear dilatation during all tests because the Poisson’s ratios were smaller than 0.5. It indicates that the marine silty clay tested in this paper has a good stability under cyclic loads.

scholarly journals The effect of confinement in liquefaction tests carried out in a cyclic simple shear apparatus

2019 ◽  
Vol 92 ◽  
pp. 08002 ◽  
Author(s):  
Lucia Mele ◽  
Stefania Lirer ◽  
Alessandro Flora
Keyword(s):  
Simple Shear ◽  
Initial Conditions ◽  
Confining Pressure ◽  
Cyclic Stress ◽  
Shear Tests ◽  
Liquefaction Resistance ◽  
Pressurized Water ◽  
Cyclic Stress Ratio ◽  
Complex Behaviour ◽  
Continuous Rotation

The cyclic simple shear tests can be used to reproduce in laboratory the complex behaviour of the soil during an earthquake, simulating the continuous rotation of the principal stress axes. In this research a comparison of results between cyclic simple shear tests carried out with confining pressure or confining rings is reported. A cyclic simple shear apparatus is used to carry out tests with confining rings (the conventional way to carry out cyclic simple shear tests) and with a confining pressure applied to the specimen through pressurized water, where the K0 condition during consolidation is guaranteed by a sophisticated control system. The apparatus, in both the configurations, is described in detail. All tests were carried out on reconstituted specimens of an Italian sand with similar initial conditions, such as low relative density and confining pressure. All experimental results are reported in the plane cyclic stress ratio (CSR) and number of cycles where liquefaction occurs (Nliq) in order to evaluate the effect of confinement on the liquefaction resistance of the studied sand.

scholarly journals Soil Liquefaction Assessment Using Soft Computing Approaches Based on Capacity Energy Concept

Geosciences ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 330
Author(s):  
Zhixiong Chen ◽  
Hongrui Li ◽  
Anthony Teck Chee Goh ◽  
Chongzhi Wu ◽  
Wengang Zhang
Keyword(s):  
Relative Density ◽  
Soft Computing ◽  
Earthquake Engineering ◽  
Textural Properties ◽  
Confining Pressure ◽  
Soil Liquefaction ◽  
Multivariate Adaptive Regression Splines ◽  
Soil Parameters ◽  
Liquefaction Resistance ◽  
Energy Concept

Soil liquefaction is one of the most complicated phenomena to assess in geotechnical earthquake engineering. The conventional procedures developed to determine the liquefaction potential of sandy soil deposits can be categorized into three main groups: Stress-based, strain-based, and energy-based procedures. The main advantage of the energy-based approach over the remaining two methods is the fact that it considers the effects of strain and stress concurrently unlike the stress or strain-based methods. Several liquefaction evaluation procedures and approaches have been developed relating the capacity energy to the initial soil parameters, such as the relative density, initial effective confining pressure, fine contents, and soil textural properties. In this study, based on the capacity energy database by Baziar et al. (2011), analyses have been carried out on a total of 405 previously published tests using soft computing approaches, including Ridge, Lasso & LassoCV, Random Forest, eXtreme Gradient Boost (XGBoost), and Multivariate Adaptive Regression Splines (MARS) approaches, to assess the capacity energy required to trigger liquefaction in sand and silty sands. The results clearly prove the capability of the proposed models and the capacity energy concept to assess liquefaction resistance of soils. It is also proposed that these approaches should be used as cross-validation against each other. The result shows that the capacity energy is most sensitive to the relative density.

Triaxial Characterization of Minnesota Road Research Project Granular Materials

1997 ◽  
Vol 1577 (1) ◽  
pp. 27-36 ◽  
Author(s):  
Navneet Garg ◽  
Marshall R. Thompson
Keyword(s):  
Shear Strength ◽  
Granular Materials ◽  
Resilient Modulus ◽  
Axial Strain ◽  
Confining Pressure ◽  
Engineering Properties ◽  
Shear Tests ◽  
Road Project ◽  
Load Tests ◽  
Repeated Load

Six granular materials were used as base and subbase materials in the flexible pavement test sections for the Minnesota Road Research (Mn/ROAD) project. Crushed/fractured particles are not allowed in aggregate classes CL-1Fsp, CL-1Csp, CL-3sp, and CL-4sp. Ten to 15 percent crushed/fractured particles are required for CL-5sp. One hundred percent crushed/ fractured particles are required for CL-6sp. A comprehensive laboratory testing program was established to determine pertinent engineering properties of the granular materials. Rapid shear tests and repeated-load tests were conducted to determine the shear strength parameters (friction angle and cohesion), resilient modulus, rutting potential, stress history effects on shear strength, and moisture susceptibility. The results from the rapid shear tests and permanent deformation tests show that the rutting potential of a granular material can be characterized from rapid shear test at a confining pressure of 15 psi (103.35 kPa). The rutting parameter A was a function of the shear strength of the granular materials. The shear strength results obtained from rapid shear tests performed at a confining pressure of 15 psi reflect the rutting trends observed in the low-volume road test sections at the Mn/ROAD project. Results from repeated-load tests were used to develop the parameters for K-θ, UT-Austin, and Uzan’s models for evaluating the resilient modulus of granular materials. The axial strain values calculated from the resilient modulus models appear to be in good agreement with the measured axial strain values, except for the very low shear strength material CL-1Csp.

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.

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