Effects of Moisture Content on the Dynamic Response and Failure Mode of Unsaturated Soil Slope Subjected to Seismic Load

Understanding the relationship between the moisture content of unsaturated soil and the instability and dynamic response of slope under the action of seismic load can bring convenience to the field of slope safety assessment. The effect of moisture content of the unsaturated soil on the failure mode and dynamic response of slope under seismic loading was investigated using shaking table tests. In this regard, three different moisture contents of 5%, 8.1%, and 12.5% were considered. The experimental results show that the amplification factor of acceleration (AFA) on the slope surface increases with the increase in both relative elevation and excitation amplitude of acceleration (EAA). As the moisture content of unsaturated soil increases, AFA tends to decrease. An empirical correlation describing the relationship among AFA, relative elevation, dimensionless EAA, and moisture content of unsaturated soil was proposed. The excitation frequency of acceleration (EFA) has a significant impact on the AFA at the middle and upper parts of the slope. The deformation of slope surface is able to reflect the failure mode of slope, which can be used in slope monitoring work. The slope with different moisture contents of unsaturated soil has different instability modes. With the increase in soil moisture content, the slope needs more energy to reach the unstable state under seismic loading. There are three typical regions of principal stress field in the slope exposed to seismic loading, which control the evolution of initial slip plane inside the slope.