Experimental Study on Changes in Site Soil Properties Before and After Seismic Excitation in Stratified Liquefaction Sites on Vibration Tables

Sand liquefaction is one of the primary hazards causing site failure in earthquake engineering. Current research predominantly focuses on the liquefaction phenomenon itself and the response of superstructures, while systematic investigations into the physical and mechanical property changes of the site soil following liquefaction remain relatively scarce. This study designed and conducted a shake table test on a layered sand-clay model site. By comparing and analyzing pre- and post-shake values of hammer blows (pen test), shear wave velocity (wave velocity test), and surface settlement before and after the earthquake. By integrating post-earthquake key indicators such as moisture content, density, and shear strength parameters (direct shear test) of the layered soil, this study systematically reveals the transformative effects of liquefaction on site soil properties. Results indicate that saturated sand layers undergo significant drainage and reconsolidation post-liquefaction, substantially increasing hammer blows and shear wave velocity while inducing considerable surface settlement. The underlying clay layer exhibits relatively minor property changes, though its moisture content slightly increases due to drainage effects from the upper layer. This study provides crucial experimental evidence for understanding post-liquefaction site performance evolution and post-earthquake foundation reuse.