Cushioned helical-piled raft systems to mitigate hazards associated with normal faulting

Abstract

Recent earthquakes leading to the emergence of surface fault rupture (SFR) on the ground surface have indicated disastrous damage to buildings. As avoidance is not always possible, proposing mitigation strategies have become quite popular with geotechnical engineers. Given that the performance benefits of helical piles outweigh other piles, the present study investigates the possibility of using cushioned helical-piled raft systems close to active normal faults to mitigate fault-induced deformations. An experimentally validated finite element code considering the critical state of the sand is implemented in this study. The response of cushioned helical-piled raft system to different distances of the raft of the system from the SFR is studied comprehensively, and the results are compared with a cushioned pipe-piled raft system with the same ultimate bearing capacity. The results reveal the superiority of using cushioned helical-piled raft systems in the vicinity of an active normal fault in terms of reducing raft rotation up to nine times, as well as lower values of the fault-induced structural response of the piles. Also, a parametric study on the geometrical aspect of helical piles shows that fault-induced angular rotation of the raft is highly dependent on it.