Study On Shoring Structural Type And Shoring Time In Underground Tunnel

In this paper, based on simulation modeling laws of geometry, constitutive relations, stress conditions and construction, a simulative calculation model has been proposed by considering the mechanical problems during the underground tunnel's construction and adopting constitutive models of enveloping type which can consider elasto-plastic materials and their cracking. The model can describe rock multi-media characteristic consider the interrelation of shoring structure and stratum reflect some influencing factors, for example: faultage interlayer joints, construction process and so on. Regularly riled criterion and constitutive model to rock mass are described in this paper. Sometimes four-parameter yield criterion which may degenerate to other regularly yield criterions in some certain conditions are described, too. In this paper, the dominated equations formed from nonlinear FEM are derived through incremental theory, and the corresponding formulations of iterative method for solving the nonlinear dominated equations are described.To truly reflect complex geometrical layout of bolts, a composite model of three-dimension anchored rock mass has been proposed for numerical simulation. The corresponding formulation of anchored mass's combined units has been formed by displacement interpolation theory of FEM and statical effective principle. And the corresponding detailed rules has also been advanced.To maintenance the stability of underground tunnel, the problems have always been discussed about how to take reasonable and timely shoring. Based on analytical method of construction mechanics, the simulative computational FEM formulations about multi-stage excavation of underground tunnel and timely shoring are prescribed. For some tunnel's construction, the stability of surrounding rock shoring mode, shoring time and so on have been studied.Based on the calculated results, the stability of surrounding rock of some tunnel and the shoring's rationality are evaluated. The shoring structure includes anchor, wire mesh, liner, skew cancelled steel framework and so on. It has been proved rationale and feasible to use different shoring project and shoring time for different surrounding rock type.