| As a relatively new method, the energy-based procedure to evaluate the liquefaction potential of soil deposits provides a better understanding of liquefaction phenomena because it can interpret liquefaction from various perspectives. Although the energy-based procedure has been proven promising and successful based on laboratory tests, less confirmation in field situations has been presented. With the successful preliminary verification based on centrifuge tests by Dief (2000), it is a logical step to examine its validity under field conditions.; Understanding the cyclic behavior of silty sands or sandy silts subjected to earthquake loading is badly needed in engineering practice. Compared to clean sands, the mechanism of liquefaction of soils with high fines content has been less investigated. In order to address the liquefaction potential of such soils from the energy perspective, a series of torsional shear tests on thin hollow cylindrical samples consisting of host sand with various fines content were conducted. The liquefaction resistance quantified by the unit energy was examined in terms of void ratio, relative density, and sand skeleton void ratio, respectively. It has been shown that liquefaction resistance of granular soils is a matter of active particle contacts, and that “skeleton void ratio” provides a better index to such contacts for silty sands under the limiting fines content.; Based on the numerical procedure to estimate seismic response of level ground proposed by Liang (1995), a modified version is developed so as to incorporate the effects of multi-dimensional loading. In addition, a bi-linear degradation model of shear strength and stiffness is proposed in this modified numerical procedure to simulate the degradation characteristics of soils under field conditions. The seismic responses of two soil deposits at well-documented sites were simulated using the modified numerical procedure. The predictions made by the energy-based procedure are generally in good agreement with actual observations at these sites. The agreement between the measured and recorded pore pressure time histories also suggests the validity of the energy-based pore pressure model. In short, the energy-based procedure to evaluate liquefaction resistance is applicable to engineering practice although additional case history verifications are still required. |
