Abstract: It is known that bedrock fault movement can cause the deformation of overlying soil during an earthquake. However, the mechanisms of fault propagation in layered cemented soil and the influences of pre-existing fracture on soil have not yet been fully understood. In this study, four centrifuge tests were conducted on 9-layered soil of clay and sand to investigate the effects of cementation and tip depth of pre-existing fracture. Centrifuge testing results show that the layered uncemented soil was subjected to deform by the shear force after normal faulting. Then, an upside down trapezoidal distribution of uneven settlement area was formed, and a shearing localization zone was also developed above the bedrock fault. When the uneven settlement finally reached the ground surface, tensile ruptures were formed at the top of the unsaturated clay layer. The bending deformation found in the layered cemented soil induced the shearing and tensile ruptures. The depth of surface fault ruptures in cemented soil was greater than that observed in the uncemented soil. In layered cemented soil, with increasing the tip depth of pre-existing fracture, the dip angle of the rupture initiating from the tip of the pre-existing fracture increased, and the surface fault rupture moved towards the hanging wall.

Key words: geotechnical centrifuge, fault rupture propagation, pre-existing fracture, cemented soil