Effect of Seismic Loading on Porewater Pressure in Clayey Soil under Disconnected Piles-Raft Foundation

The disconnected piled raft foundation (DCPRF) is one of the newly introduced foundations for specialization in geotechnical engineering, which significantly reduces the moment and stress on the pile head. In addition, this type of foundation is an ideal choice in areas with seismic activity due to the presence of cushion material between the raft and the piles. This work aims to present a numerical model in PLAXIS 3D software for connected piled raft and disconnected piled raft foundations under the influence of seismic loads and investigate the effect of pore water pressure on the disconnected foundation compared to the connected foundation. The study will depend on the earthquake that struck Iraq in November 2017 in the Halabja region. Strength was 7.3 on the Richter scale with PGA (0.1g). The results of changing pore water pressure showed the variation of pore water pressure. In the case of a DCPRF, the porewater pressure and excess porewater pressure in the soil are much greater than in the case of a CPRF. The increase in the porewater pressure is due to the weight of the building and the weight of the additional cushion layer on the soil. The mechanism for transferring the load in the case of a DCPRF is carried out by raft, then to the cushion, and then to the soil and piles. The load transferred to the soil in the case of DCPRF is more than that transferred to the soil in the CPRF system.