Dynamic Response of Saturated Kaolin Clay under Repeated Impact Loading

The dynamic response mechanism of clayey foundations under impact loading remains insufficiently understood. This study investigates the dynamic behavior of saturated kaolin clay under repeated one-dimensional impacts using an improved Split Hopkinson pressure bar (SHPB) apparatus. Tests were conducted under different water contents, impact velocities, and specimen thicknesses, with silica sand used for comparison. The results show that saturated kaolin clay exhibits a distinct dynamic evolution mechanism governed by transient pore-water pressure, loosely adsorbed water films, and soil particles. Its peak stress is approximately 1.2-2.0 times that of silica sand, whereas its residual strain is about 0.5 times that of silica sand. Repeated impacts progressively densify the kaolin clay, increasing its dynamic apparent modulus to 2.0-4.0 times the initial value and its yield pressure to 1.9-3.9 times that of silica sand. The cutoff stress of energy absorption is about twice that of silica sand, whereas the peak energy absorption efficiency is about half. The best fitted empirical equations for peak stress and dynamic apparent modulus were obtained within the tested conditions.