There exist two types of finite deformation theorems in large deformation process of deep soft rock engineering, i.e. polar decomposition theorem and additive decomposition theorem. In this paper, referring to the functional expression between geostress and the depth proposed by Brown and Hock, the additive module and the polar decomposition module included in A Software on Large Deformation Analysis for Soft Rock Engineering (LDEAS) at Great Depth were adopted respectively to simulate the effect of geostress on the large deformation induced in the process of the excavation of Jia-he Mine at −800m level. The results indicate that: the sidewall shrinkage, floor heave and roof caving represent a positive linear relationship with the depth and the increasing rate of the mount of floor heave is the fastest. Moreover, the mount of the deformation calculated by solar decomposition module is relatively smaller than the corresponding result obtained through the polar decomposition module.
As the depth of excavated tunnels increases, the geostress value is increasing and deformations of the surrounding rock masses are generally large, such as roof caving, floor heave and sidewall shrinkage, which contribute to the increasingly difficulties of the tunnel supporting. Therefore, the determination of the initial geostress field is essential to the design of the tunnel supporting and construction and it affects the economical efficiency, reliability and safety directly. As a result, it is necessary to study the influence of geostress in the excavation of a tunnel. In the large deformation analysis of a deep soft rock tunnel, appropriate nonlinear kinematic theories to measure strain and rotation are needed in addition to reliable geostress field. In this paper, the focus is on the different influence of geostress on the deformation of a deep soft rock tunnel based on different large deformation theories.