Centrifuge modeling of failure patterns in mixed soil layers induced by normal faults

Ground failures and ruptures may be induced by fault movements during an earthquake. Numerous notorious earthquakes including the recent Wenchuan earthquake have revealed that surface fault ruptures cause serious damage to structures located near bedrock fault zones. Physical model tests have been conducted by various researchers to investigate the influence of fault movements at one gravity (1-g) and elevated gravity. Most of these physical model tests have been carried out on clear dry sands even though very complex ground failure patterns have been observed in field case studies. In this study, three centrifuge model tests at 120-g were conducted to observe ground failure patterns in different types of soil. Three different models, a sand model, a silt model and a model with mixed soil layers, were tested in the centrifuge. A newly developed hydraulic setup was used at the bottom of the centrifuge models to simulate normal bedrock fault movement with a dip slip angle of 70° with respect to the horizontal direction. The centrifuge setup, model preparation and testing procedures and experimental results are described, reported and discussed in this paper. © 2009 IOS Press.