Experimental study on the dynamic responses of pile-raft foundation of high-rise building in liquefiable site

The objective of the current investigation is to delineate the dynamic response mechanism of piled raft foundation supporting high-rise structures in the context of liquefiable sandy soil under the influence of intense seismic activity. Within the scope of this study，a scaled-down model representing the integrated system of saturated sand strata，piled raft foundation，and high-rise edifice has been meticulously designed and fabricated. Utilizing the centrifuge shaking table apparatus，dynamic response assessments under varying degrees of ground motion intensity have been conducted. The study primarily concentrates on the analysis of soil acceleration responses，variations in excess pore water press ratio，dynamic behavior characteristics of high-rise structural systems，and the underlying dynamic response patterns of pile-raft foundations. Furthermore，the investigation delves into the interrelation between soil liquefaction and the dynamic response of the pile-raft foundation system of high-rise buildings. The empirical findings indicate that the piled raft foundation of high-rise buildings exacerbates the depth of soil liquefaction to a certain degree，with the dissipation of pore pressure occurring at a leisurely pace amidst the pile clusters. The amplitude of acceleration response spectra diminishes with the progression of soil depth. During the occurrence of minor seismic events，the acceleration of the raft tends to escalate，whereas，in the case of major seismic events，the acceleration response of the raft exhibits an initial increase followed by a subsequent decrease. As the peak acceleration of seismic waves intensifies，the maximum bending moment experienced by the pile shafts progressively diminishes，with the upper bending moment of the central pile being more pronounced. Moreover，the maximum bending moments of corner piles，side piles，and central piles are observed at the interface between the sandy soil layers. The liquefaction of the foundation soil provides a damping effect for the superstructure to a certain extent.