| dc.description.abstract | Permanent ground displacement due to the fault slip is a concern to infrastructures adjacent to the active fault. For instance, severe and serious damages happened during the big earthquake like Chi-Chi earthquake in Taiwan and Kocaeli and Duzce earthquake in Turkey at 1999. These 3 disasters are the turning point on put more concern on the behavior of the fault slip to either to the soil deposit itself or the building and infrastructure located in the fault affected zone. Furthermore, natural soil deposit is rarely found to be homogeneous and uniform, some part of the soil has higher strength layers, like soft rock stratum, at the bottom of the soil strata, causing some complex behavior while the fault rupture is propagating through both soft rock and soil strata.
In this study, 8 centrifuge modelling test simulating both reverse fault and normal fault are conducted to observe mechanism of soft rock base layer affects the whole soil deposit surface. The soft rock layer is simulated by using a mixture of accelerated sand and cement. Both uniaxial compression tests and direct shear tests are conducted to evaluate the strength of the different proportion of cement. All the mixture is cured for 7 days before it tested. The 5% cement mixture is selected due to its uniaxial compression strength of 0.975 MPa, which can simulate soft rock and have a brittle mode as the post-failure behavior. The Mohr–Coulomb failure criterion is 43.5 degrees and 148 kPa of friction angle and the cohesion. The upper layer stratum is pluviated quartz sand with 37 degrees of friction angle at unit weight of 15.6 kN/m3. The model have different thickness ratio between soft rock layer and sandy layer with 100 mm total soil deposit thickness, which is corresponded to 8 meters in the prototype scale in 80 g centrifugal acceleration field.
Based on the experiments results, it shows that: (1) The thickness ratio of the rock stratum plays a major role for the length of the affected zone in both reverse fault and normal fault simulation; although, the affected zone for the normal fault reach maximum length when the sandy soil ratio at 30%. (2) The thickness ratio between the soft rock layer and sandy soil layer affects the crack propagation in soft rock stratum, the crack propagates to wider area as thinner sandy soil thickness. (3) In both normal fault and reverse fault slip, the surface distortion is dependent on type of material at the bottom layer. (4) The deformation of the rock-based strata has the widest, due to its crack propagation and the sand based layer has the narrowest deformation zone, due to its narrow rupture propagation at based layer. | en_US |