Static Liquefaction Assessment Combining Shear Wave Velocity, Peak Strength and Soil Grading (original) (raw)
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SHEAR STRAIN DEVELOPMENT IN LIQUEFIABLE SOIL UNDER BI-DIRECTIONAL LOADING CONDITIONS
A comprehensive testing database composed of modeling-quality multi-directional cyclic simple shear testing on medium to high relative density, fully-saturated samples of Monterey 0/30 sand has recently been developed. This testing program incorporated a variety of multi-directional stress paths, including a large number of stress paths never before examined. Results from these tests have proven useful for enhancing current understanding of liquefaction behavior by allowing for a more complete theory to emerge. This new 3-dimensional theory greatly expands current understanding of liquefaction behavior and elucidates some areas in which current theory—which has been based principally on uni-directional laboratory testing—can be misleading or unconservative. Of particular interest are the topics of pore pressure generation and softening, the relationship between pore pressure and strain capacity, and the dilational lock-up in medium density sands that acts to limit large free-flow type deformations. Insight has also been gained on the complex effects caused by an initial static shear stress such as would be imposed by sloping ground conditions or the presence of a structure.
Liquefaction assessment from laboratory tests on undisturbed and reconstituted silty soil specimens
2018
Liquefaction charts constructed from in situ tests (e.g. SPT, CPT) and susceptibility criteria are often used for granular and fine-grained soils. With good sampling of clay-like soils, laboratory tests can be used with confidence to assess liquefaction or cyclic softening behavior. For silty and sandy soils, it is difficult to obtain undisturbed samples and also difficult to restore all field conditions (lost by disturbance) with the reconstitution of these materials. However as shear wave velocity, Vs can be measured both in field and in laboratory, and thus it could serve as a reference to reconstitute soil samples. In this paper, a new approach based on experimental and theoretical results is used to assess liquefaction potential (or cyclic softening). Measurements of Vs in laboratory have been utilized to examine the potentiality of using the Vs1-e correlation (where Vs1 is the stress-normalized shear wave velocity) as a reference to reconstitute silt specimens. Then, a series ...
2016
The liquefaction resistance of soils can be evaluated using laboratory tests such as cyclic simple shear, cyclic triaxial, cyclic torsional shear, and field methods such as Standard Penetration Test (SPT), Cone Penetration Test (CPT), and Shear Wave Velocity (Vs). The present study is aimed at comparing the results of two field methods used to evaluate liquefaction resistance of soil, i.e. SPT based on simplified procedure proposed by Seed and Idriss (1985) and shear wave velocity (Vs) on the basis of Andrus et al. (2004) process using empirical relationships between them. Iwasaki’s (1982) method is used to measure the liquefaction potential index for both of them. The study area is a part of south and southeast of Tehran. It is observed that there is not a perfect agreement between the results of two methods based on five empirical relationships assuming cemented and non-cemented conditions for (OF) soil. Liquefaction potential index (PL) value in SPT test was found to be more than...
Journal of Structural Engineering and Geo-Techniques, 2012
The liquefaction resistance of soil can be evaluated using laboratory tests such as cyclic simple shear, cyclic triaxial, cyclic torsional shear as well as field methods like Standard Penetration Test (SPT), Cone Penetration Test (CPT) and Shear Wave Velocity (Vs). In this regard, this study attempts to compare the results of the SPT based on the simplified procedure proposed by Seed and Idriss (1985) and those of the Vs on the basis of Andrus et al.’s (2004) process using empirical relationships between them. Iwasaki’s (1982) method is used to measure the liquefaction potential index for both of them. The study area is a part of the south and southeast of Tehran. It is observed that there is not a perfect agreement between the results of the two methods based on five empirical relationships assuming cemented and non-cemented condition for soils. Moreover, the liquefaction potential index (PL) value in the SPT method is more than that of the Vs method. Keyword: Liquefaction, Standar...
Related to Liquefaction Susceptibility of Silty Soils
1999
The liquefaction susceptibility of silty soils has not received the same level of emphasis as sandy soils. This paper presents some observations related to liquefaction susceptibility of silty soils based on the analysis of data from seven sites. The data includes cyclic triaxial and cyclic simple shear tests conducted on undisturbed samples of soils and index and grain size data on the same samples. The applicability of the commonly used Chinese criteria for the assessment of liquefaction susceptibility of fine-grained soils such as silts is examined using the laboratory test results. The characteristic cyclic loading behaviour of silty soils is compared with that of sandy soils, and parameters that are required for the assessment of deformations are identified and their anticipated range in values discussed.
Liquefaction risk assessment is critical for the safety and economics of structures. As the soil strata of Ramsar area in north Iran is mostly composed of poorly graded clean sand and the ground water table is found at shallow depths, it is highly susceptible to liquefaction. In this study, a series of isotropic and anisotropic consolidated undrained triaxial tests are performed on reconstituted specimens of Ramsar sand to identify the liquefaction potential of the area. The specimens are consolidated isotropically to simulate the level ground condition, and anisotropically to simulate the soil condition on a slope and/ or under a structure. The various states of soil behavior are studied by preparing specimens at different initial relative densities and applying different levels of effective stress. The critical state soil mechanics approach for identifying the liquefaction susceptibility is adopted and the observed phenomena are further explained in relation to the micro-mechanica...