Experimental Study on Concrete Similitude Material Model Piles and Numerical Simulation Analysis of Dynamic Response of Saturated Silty Sand-Pile Group Systems

To address the challenge of balancing high density with low elastic modulus in physical model tests of liquefiable foundations, this study proposes a novel concrete similitude material and numerically investigates the dynamic response of saturated silt-pile systems. Based on Buckingham π theorem, the mixture of barium sulfate and blast furnace slag was optimized by changing the ratio of sand to stone powder under the condition of 1 g, with Portland cement, natural sand, barium sulfate powder and blast furnace slag powder as raw materials. Subsequently, 3D numerical simulations using MIDAS GTS NX 2023 v1.1 evaluated pile-soil interactions under varying seismic intensities. The results show that the optimal mixture achieves a density of 2.083 g/cm3 and an elastic modulus of 0.65 GPa, accurately simulating C30 concrete at a 1:30 scale. Simulations indicate that shallow soils liquefy first under 0.2 g seismic loading. Pile groups significantly delay liquefaction and reduce excess pore water pressure by 15–20% compared to free-field conditions. Furthermore, they regulate acceleration bilaterally: before liquefaction, piles restrict soil shear deformation, reducing surface acceleration amplification from 6.0 to 3.2; after liquefaction, their rigidity alters wave propagation, diminishing the soil’s vibration isolation effect. These material innovations and elucidated anti-liquefaction mechanisms provide a robust scientific foundation for large-scale shaking table tests and the seismic resilience evaluation of pile-supported structures.