AN EVALUATION OF SINGLE PILE AND PILE GROUP BEHAVIOR UNDER SEISMIC LOADING IN SOFT GROUND

This paper investigates the seismic behavior of single pile as well as pile group in soft soil through three-dimensional finite element simulation. The computational model is developed using Plaxis 3D programme, in which the used geotechnical parameters are obtained from a geotechnical investigation in Dong Thap Province. Seismic loading is modeled as vertically propagating shear waves with a peak ground acceleration (PGA) of 0.07g according to the Vietnamese standard TCVN 9386:2012. The analysis indicates that when single pile is subjected to seismic loading, the maximum shear force and bending moment increase by 42.5% and 62.1%, respectively, compared to static conditions; (2) For a 3×3 pile group with a rigid cap, these corresponding increases are more significant, reaching 192.5% in shear force and 72.4% in bending moment. Although the internal force in group pile is higher, the settlement of group pile reduces approximately 50%, compare to the single pile case, thereby indicating well performance in overall system stability. Moreover, the ground response analysis shows the motion amplification is about 2.0 to 2.5 times within the 6–20 second, emphasizing the effect of wave amplification in soft deposits. The findings highlight that the consideration of soil–pile–seismic interaction in the foundation design is very necessary, advocating the use of nonlinear dynamic modeling to ensure safety and well performance of structures under seismic excitation.