A nonlinear, three-dimensional finite element model was applied to simulate the conventional procedure of underground workhouse excavation. The Drucker-Prager elastic-perfectly plastic material model was used for the simulation of rock mass, faults and the supporting structures. The material non-linearity was dealt with using an incremental technique. In monitor the stability of powerhouse cavern, the displacements of surrounding rock were measured during excavation. The field measurement results show that the surrounding rock of cavern is stable while the rock bolt and shotcrete were designed as the supporting structures. Maximum deformation of cavern surface is less than 6mm after 840 days. The most deformations of surrounding rock reached the stable states after the cavern excavation was finished. The principal and secondary factors affecting deformations of surrounding rock are spatial and temporal effect, respectively. The rock excavation for different stage in the measurement section played important role for the deformations of surrounding rock of cavern.
One of the most important and commonly met problems in underground engineering concerns the assessment of stability of underground caverns according to the displacements measured during the excavation works and the stress distribution simulated by using finite element method. In situ measurements are nowadays frequently carried out during the excavation of large-scale caverns in order to monitor the stability of the openings. A great variety of excavation technology has been developed, which employ different methods to reinforce and support the excavation front. Tezuka (2003) discussed latest technology of underground rock cavern excavation in Japan. The technologies proposed in the paper have some unique characteristics and can be applied to various other underground uses for different purposes and applied to large-scale underground rock caverns with different geological and in situ stress analysis. Eberhardt (2001) investigated the numerical modeling of three-dimension stress rotation ahead of an advancing tunnel face. The research results demonstrated that as the tunnel face approaches and passes through a unit volume of rock, the spatial and temporal evolution of the three-dimensional stress field encompasses a series of deviatoric stress increases and /or decreases as well as several rotations of the principal stress axes. Karakus (2003) simulated sequential excavation model of underground tunnel by using ABAQUS software and a number of finite element method were conducted to investigate the effects of different patterns for advancing the tunnel face on the settlement. Hao (2005) researched the plastic zones and displacements around underground openings in rock masses containing a fault. The relationship of the induced plastic zones, maximum displacements varying with these fault parameters was established. Farias (2004) analyzed displacement control in tunnels excavated by the New Austrian Tunneling Method. Induced displacement are empirically controlled by adjusting the speed of excavation, distance between tunnel face and support, partial-face excavation and closure of invert. This paper attempts to investigate the simulation of excavation process, stress distribution and stability of surrounding rock of large-scale cavern by using finite element method, and to apply the displacement field measurement of surrounding rock for evaluating rock mass stability and supporting reliability.
