Study on the seismic responses and differences between rock-socketed single pile and pile group foundations under different scour depths

The effects of scour depth on the seismic responses of rock-socketed single pile foundations and 2 × 2 pile group foundations were investigated by shaking table tests, and the seismic performance and differences of these two foundation types were analyzed. The test results show that increasing scour depth causes liquefaction to occur earlier but also accelerates the dissipation of pore water pressure. Pile acceleration, pile top displacement, and pile bending moment all increase with increasing in scour depth. The pile top acceleration and amplification factor of the pile group increase steadily and linearly with increasing scour depth, while those of the single pile increase abruptly at the anchorage ratio of 4.6. The acceleration amplification effect is also susceptible to the types of soil layers and the stiffness of the pile body. The stability of pile group deformation is assessed to be superior to that of single pile based on the amplification intersection line. The maximum bending moment of the pile body arises at the interface between saturated sand and strongly weathered granite, and its location does not shift with increasing scour depth. Increasing scour depth not only amplifies the adverse effects of seismic excitation on pile acceleration, pile top displacement, and pile bending moment but also amplifies the differences in seismic performance and liquefaction resistance of these two foundation types. Based on the research results, pile group foundations have better seismic performance than single pile foundations because of the load-sharing effect of the pile group under different scour depths. Therefore, pile group foundations can provide more stable support in scour-prone areas.