Effect of Geosynthetics-Reinforced Cushion on the Behavior of Partial Connected Piled Raft Foundation in Dry and Saturated Sandy Soil Using Shaking Table

A partially connected piled raft foundation technique is utilized to protect the system of the building-piled-raft foundation against horizontal and vertical displacements. At the same time, the dynamic characteristics of the structure and load transfer mechanism will be affected by the geosynthetic reinforcement in the cushion layer separated between raft and piles. The seismic behavior of the partially connected piled raft foundation system under an earthquake in dry and saturated sand soil has not been thoroughly investigated. This study investigated the behavior of partially connected piled raft foundation with a cushion layer reinforced by geosynthetic materials in dry and saturated sand soil under seismic loading. To assess the response of the cushion layer to vertical and horizontal displacements of the raft foundation, four configurations of pile models were tested using shaking table. Also, the bending moments and strain variations in the geosynthetic-reinforced cushion layer subjected to earthquake loading have been investigated. The results of tests showed that using the geosynthetic materials in the cushion layer reduces the horizontal displacement for tested models with more than one connected pile in saturation state. For the partially connected piled raft foundation, reinforcement of the cushion layer by geogrid layers reduces the deformation and consequently increases the load-bearing capacity of foundation system. For the dry soil tests, the connected piles displayed high values of bending moment at the pile’s head due to the inertial and kinematic interactions. Also, the liquefaction of surface soil layer causes raising the bending moment values in the connected and disconnected piles regardless the reinforcement of cushion layer.