Risk of surface blast load on pile foundations

Grounds and foundations, underground structures

Recent terrorist attacked has raised the importance of studying the structural response under blast loads. Most of the past research has focused on the superstructure performance without considering the foundation behavior under blast loads. In this research, a pile foundation system was analyzed using detailed finite element analysis using ABAQUS under blast load to investigate the effectiveness of different mitigation techniques. The foundation system includes nine concrete piles encased in steel pipes with external diameters of 0.6 m. The piles have a length of 20 m in silty clay and stiff clay layers. The piles are connected using a reinforced concrete raft with dimensions of 10 m×10 m and a thickness of 1 m. The blast load considered resulted from a surface explosive charge of 457 kg of TNT at a standoff distance 2.5 m from raft and at a height of 0.56 m above ground surface. The raft was loaded by 200 kN/m2 to represent the load transferred from the structure. Barrier walls from different materials including aluminum, rubber, Thermoplastic polyurethane (TPU) and Expanded Polystyrene (EPS) were considered to mitigate the blast load effect on the pile foundation. Also, an open trench before the raft was considered and compared to the used wall barriers. It was observed that the open trench and a wall barrier from Expanded Polystyrene showed the best mitigation to the blast effect compared to the original case and other wall barriers from different materials. A parametric study was conducted to optimize the selected EPS wall barrier in terms of thickness and depth.