STUDY ON MULTI-STAGE EXCAVATION EFFECT OF DEEP CUTTING WITH DUALISTIC LAYER

A railway deep cutting with the maximum excavation height of 120m gives great challenges to design and construction because of dualistic layer structure and multi-stage blasting excavation. In this paper, considering the characteristics of the dualistic layer of the slope and the structural plane of rock mass, the static and dynamic simulation of the five-stage excavation and support is carried out with both the finite element limit equilibrium method and the dynamic finite element method, thus the failure mode and factor of safety is obtained. The simulation results show that:(1)The stability of the deep cutting is gradually controlled by the fully weathered sandstone, the dualistic layer interface and the most unfavorable structural plane of the limestone along with top-down multi-stage excavation. And as the excavation increases, the ground stress is gradually released, the shear stress field is deflected, and the plastic zone becomes smaller. (2)The displacement field caused by blasting decays approximately spherically with the distance from the blast source and is amplified at the interface of the dualistic layer. The research results have important implications for the design and construction of the railway deep cutting.