Fault deformation can cause severe damage to structures located within the fault zones. A logarithmic spiral model was developed by D. A. Cole and P. V. Lade in 1984 to predict the shapes and locations of fault ruptures in sand caused by dip–slip faulting, based on 1g sandbox tests. However, it shows poor predictions for reverse fault ruptures observed in centrifuge tests. In this study, centrifuge modelling of reverse faulting was performed to explore the reasons for the poor predictions by the logarithmic spiral model. These faulting tests were conducted in free-field conditions with different sand densities and soil thicknesses. Based on results of centrifuge tests from both the present study and previous research studies, a hyperbolic spiral model is proposed to predict approximately the shapes and locations of reverse fault ruptures in sand. The results show that the 45° − ϕ_max/2 rather than 45° − ψ_max/2 controls the surface direction angle of the outcropping rupture. Validation of the hyperbolic spiral model shows a promising prediction in centrifuge tests both in the present study and previous research studies.

Previous studies have found that pile foundations will be severely damaged when subjected to faulting. However, the pile–soil interaction mechanism is still unclear due to the lack of well-documented field observations and physical model tests. In this study, six centrifuge tests were conducted to investigate the interaction of single piles and sand subjected to dip-slip faulting and to discuss some influential factors, such as fault type, pile location, uplift ratio, pile stiffness, and sand density. The responses of piles are sensitive to fault type, pile location, and uplift ratio. Piles in a reverse fault experience much larger internal forces than those in a normal fault. The fault deformation causes large internal forces on piles located within the fault zone, whereas those out of the fault zone are practically not affected. The outcropping of ruptures is a critical state for the behavior of piles both in reverse and normal faults. After outcropping, further fault movement does not cause the increment of pile bending moment, implying the maximum horizontal load is applied at the time of outcropping.