Behavior of partially connected piled raft foundation under seismic loading

A partially connected piled raft foundation is a new modification for the fully connected or disconnected piled raft foundation. The characteristics of the connected piles could transfer loads from the superstructure to the underlying soils. The disconnected piled raft foundation has an effective advantage for reducing the dynamic motion that is transmitted to the high-rise superstructures. However, the dynamic behavior of the partially connected piled raft foundation system under a strong earthquake in medium sand soil has not been thoroughly understood. In this study, the effect of the distribution of piles patterns, number of connected piles (CP), and number of disconnected piles (DP) through a series of seismic experimental model tests have been investigated. These tests were performed with 1, 4, 5, and 9 piles under different static loads. Vertical and horizontal displacements, acceleration, and variation of bending moment of soil and piles are monitored through the experimental tests. The results showed that increasing the number of CP compared with DP contributed to an effective way to reduce the horizontal displacement of the piled raft foundation system. The advantage of DP in resisting seismic loading appears when the number of DP is more than the number of CP. Due to the structural connection of the raft-pile-soil system, the CP was subjected to high values of the seismic acceleration and bending moment. The reduction in the bending moment of DP within the partially connected piles group depended on the number of CP and increasing the thickness of the cushion layer.