Liquefaction Characteristics of Four Ya-An Low-Plastic Silty Sands with Presence of Initial Static Shear Stress

Abstract

Following the construction of Sichuan-Tibet railway, further development of infrastructures can be anticipated in the cities or counties along the railway. However, these cities or counties, including Ya-An, are located in mountain areas with relatively high seismicity, making the initial static shear stress to be an important factor in soil liquefaction assessment. In this study, four low-plastic sands, which liquefied in the 2013 Lu-Shan earthquake, were extracted for investigation. A series of cyclic triaxial tests were performed to evaluate the liquefaction resistance ratios (CRR) of the four sands with different initial static shear stress ratios (α). The failure patterns of the soils were identified to be either cyclic mobility or plastic strain accumulation, depending on the cyclic shear stress amplitude and the initial static shear stress, i.e. the stress reversal conditions. The effects of initial static shear stress on the liquefaction resistance were found either beneficial or detrimental depending on the initial static shear stress level. The threshold α concept (αth) proposed by Yang and Sze [6] may be used to characterize such effects for natural sands containing a substantial amount of plastic fines. The liquefaction resistance first increases with increasing α if α αth. The αth can be estimated using the no-reversal line representing α = CRR.