Numerical analysis of seismic behaviour of soil under frozen surface conditions

抄録

In seasonal cold regions like Hokkaido, the soil surface up to a shallow depth is frozen during the winter. An earthquake during the freezing period and thawing period may cause severe disasters i.e. slope failures induced by the combined effects of seismicity and snow melt water. The influences of freezing conditions on the seismic behaviour of soil need to be studied elaborately. In this study, a series of shaking table tests were performed with frozen surface layer and numerical analysis has been performed to simulate the seismic behaviour of soil under the frozen surface state. The numerical analysis has been done based on the series of shaking table tests performed under two different conditions i.e. without a frozen soil surface layer and with 10 cm frozen soil at the surface. Loose density (Dr=30~35 %) and high density (Dr=75~80 %) Toyoura sand have been used to study the liquefaction behaviour. Different liquefaction behaviour is observed when considering surface frozen conditions under both loose and high relative densities of soil. Through the shaking table tests and numerical simulations performed, it is clear that the frozen surface layer severely affects the seismic response of the soil and if these conditions prevail on a soil slope during an earthquake, a sliding slope failure causing the movement of frozen soil layer may occur conceivably.