Study on pore pressure and fluidization evaluation method of unsaturated loess in vibration process

摘要

The large-scale fluidization failure of a loess slope induced by earthquake has been widely investigated domestically and abroad. Studies on the fluidization failure of loess slopes have mainly focused on the mechanism of loess subsidence and the liquefaction of saturated loess, while fewer studies have investigated the fluidization failure mechanism and evaluation of unsaturated loess with high water content. In this study, a series of dynamic triaxial cyclic shearing tests were carried out on unsaturated loess to elucidate the mechanism of failure resulting from the fluidization of unsaturated loess by considering the dynamic pore-water pressure, dynamic pore-gas pressure, and dynamic strain of unsaturated loess under the influence of different vibration frequency, matric suction, dynamic stress, and saturation. The results reveal the following: under undrained conditions, when subjected to continuous vibration loading, unsaturated loess can also generate extra-static pore-water pressure, which increases hysterically but quickly grows close to the initial confining pressure. At this time, samples with greater saturation are prone to fluidization failure and approach loess liquefaction. A theoretical model applicable to the fluidization of unsaturated loess is proposed according to the liquefied-evaluation method for saturated loess and the Boyle-Charles law for ideal gases. An evaluation method is also proposed. This study has important theoretical value, and practical significance for further understanding the formation mechanism of the fluidized failure of unsaturated loess slopes under vibration conditions, and for preventing and controlling slope geological disasters during earthquakes in loess regions.