Three-dimensional numerical simulation of rupture process of overlying soil caused by buried normal fault movement

The rupture process of overlying soil caused by uniform movement and inclined movement of buried normal fault was studied by setting a three-dimensional numerical model. The stress state and failure style of overlying soil are respectively analyzed by using stress Lode parameter and equivalent plastic strain during fault movement, and a discrimination method of soil rupture is recommended. The conclusions are drawn as follows through analyzing the results of numerical simulation: ① As affected by fault movement, the stress state of overlying soil on the footwall side of the fault varies via compression-shear → pure-shear → tension-shear during fault movement, and the soil stress state on the upper wall side of the fault is fairly complex, which repetitively varies via compression-shear → pure-shear → tension-shear → pure-shear → compression-shear. ② For the uniform movement of the fault, the surface soil ruptures firstly occur at the tension-shear area on the footwall side of the fault, and with fault movement increased, the ruptures develop towards both sides as well as downward. Meantime, the bottom soil failures occur on the footwall side of the fault and develop obliquely upward, and finally connected with the rupture of surface soil. ③ For the inclined movement of the fault, the positions of soil rupture are relative with the thickness of overlying soil. When the overlying soil is thick, the surface soil ruptures or ground fissures occur due to the fault movement, which have an angle with the fault strike, and are much shorter than the fault. The numerical simulations can reveal the surface soil rupture patterns and will provide the basis for the studies on the origin and distributed patterns of ground fissures.