EXPERIMENTAL STUDY OF SEISMIC RESPONSE OF THE SQUARE TUNNEL IN GRANULAR SOIL

Abstract

In this study a series of shaking table tests were carried out to investigate the effect of tunnel model depth and direction of ground acceleration on the horizontal acceleration of tunnel model and soil beside it, ground surface settlement, and the dynamic earth pressure on the tunnel wall. Square tunnel model embedded in both dry and saturated soil (Karbala Sand). It subjected to three input sinusoidal motions 0.05g, 0.1g, and 0.2g. Two relative densities used, 30% for the upper layer and 70% for the lower layer. The results obtained indicate that the direction of seismic loading has significant effect on the horizontal acceleration of tunnel model. The increase of tunnel model depth lead to decrease the horizontal acceleration of tunnel model. While, the settlement of soil surface increases with an increase of tunnel model depth and ground acceleration especially at 0.2g earthquake loading. The change of direction of seismic loading leads to a small change in the settlement for dry soil. The results appear that dynamic earth pressure (DEP) was positive in dry soil and negative in saturated soil in all test. In saturated soil, the effect of direction of ground acceleration and depth of tunnel model on DEP in 0.2g is quite little.