Abstract: Pile foundation could be severely damaged by active fault during an earthquake, resulting damage and even collapse of superstructures. The pile failure mechanism and setback distance are not yet investigated systematically. Centrifuge and numerical modeling of pile group foundation in sand subjected to normal faulting were conducted. The influences of pile location relative to the bedrock fault on failure mechanism of pile group were investigated. Centrifuge and numerical results consistently show that when the pile group crosses the bedrock fault, the pile tilts to the hanging wall after faulting and is also bent to the hanging wall. Loading redistribution between piles results in two different failure patterns of tension and compression. Numerical parametric study of pile locations show that five characteristic zones could be classified based on different pile responses. For a soil stratum with thickness of 20.0 m, the setback distances of pile group at the side of footwall and hanging wall are 15.9 m and 23.5 m, respectively. The area within 7.9 m to the fault line at the footwall and 4.1 m to the fault line at the hanging wall is the most critical setback zone.

Key words: geotechnical centrifuge, numerical modeling, normal fault, pile group, setback distance