MODELING TEST OF NORMAL FAULT RUPTURE PROPAGATION IN SANDY SOIL

Fault movement cannot only cause earthquake, but also bring about permanent deformation in strata. They have great damage to structures, especially linear structures like underground pipelines and tunnels unavoidably. The Kobe earthquake in Japan in 1995 and the Taiwan Chi-Chi earthquake in 1999,the WenChuan earthquake in China in 2008 have all caused to large losses of lives and properties. Active faults are widely distributed in China. Therefore, study on earthquake fault rupture propagation in overlying strata is essential. Many scholars at home and abroad have paid attentions to this subject. Modeling test, centrifuge test and numerical method are used to research the problem. Generally the damages induced by surface rupture are considered as a result of discontinuous deformations of overlying soil resulting in vertical or lateral offset at the surface of soil. However, due to the reason of the complexity of geological and stratigraphic conditions, the limitation of research and field monitoring methods, the question still does not have a clear answer. On the base of sand box, the paper aims to reveal the patterns of fault rupture propagation and location of surface rupture in sandy soil under 1-g modeling test of normal fault. It also studies the relationship between vertical displacement and height of overlying strata.that the following results are found. The failure surfaces of normal fault begin to propagate directly up to the surface regardless to dip angle. Then the following failure surfaces appear. The required vertical displacement when a complete failure surface forms is independent with the dip angle. In the modeling test, the value of D/H comes out to be 4.4%.As many failure planes exist when fault rupture propagates, an apparent triangle shear zone stays between them. At the surface, the width of the triangle shear zone reaches a maximum S.The value of S becomes greater as the dip angle decreases.