The Analysis Of 3-D Numerical Model And Reliability Of Tunnel Structure

With the construction of the west of our country developing at top speed and the need of construction of mountainous expressway, the tunnel engineering,especially the tunnels on the mountainous expressway,will be increased. If the design of support structures of the tunnel still adipts traditional design methods,it will be difficult to give full considerations for the reasonability in economy of the sections of the support structures and for the reliability of bearing capacity and stability of the support structures. The characteristic of structural reliability is described by structural reliability, with makes the structure design more scientific,reasonable than traditional method,and it can further reflect the essence of the question studied.This paper firstly studies the characteristics of initial stress fields for Xuefengshan tunnel, which is Crossed by Shao Yang-Huai Hua expressway in Hunan,and than comprehensively analizes the test results of ground stress field obtained by means of the methods of hydraulic fracturing,indoor Kaiser effect and three-hole intersection aperture deformation. Based on the test results,the distribution of initial stress fields is simulated through non-linear finite element method. Compared with this two results,it is concluded that the simulation results are basically in consistence with the test results. The maximum principal stress value on tunnel plane is 16.7 MPa ³3.2MPa,and the minimum principal stress is 0.1 MPa ⁵.4MPa.The principal stress regularly increases with depth increasing,but because it is controlled by the mechanical properties of rock and structural features,stress differentiation phenomena will be appeared in soft and hard rock layers and nearby fault zones. The maximum value of maximum principal stress is not in the deepest buried place of tunnel,but in near east direction,which shows that geological structure plays a great role on distribution of main stress,and tectonic stress field is relatively high in tunnel place. On the basis of study of initial stress fields,the change law of surrounding rock and supporting structure in construction is understanded. These research results provide more reference for disaster prediction and management,meanwhile provide accurate initial condition for three-dimensional numerical simulation and reliability calculation.Focused on the practical situation of the Xuefengshan tunnel project,this paper discusses the variations of the deformation and stability causing by space effect of the tunnel structure, inorder to provide the rational support in construction,by the research of the engineering geology condition of the tunnel site including the regional geology,regional stability,topography condition,stratum lithology,geological structure,stress field evolution,hydrogeological conditions and so on,combined with monitoring of arch settlement,tunnel convergence, surface subsidence,rock deformation and rock deformation after supporting and using FLAC^3D the 3-D non-linear numerical analysis. At the same time,constructing functional function and variation distribution state to analyse the stability and reliability of the XueFengShan tunnel structure in the method of Response surface method and Monte-carlo method. Through 3-D non-linear numerical analysis and the margin of safety achievement contrast analysis, as well as the tunnel displacement monitor result, stability analysis and structural optimization is done,and some beneficial opinion suggestion is also provided to the tunnel designer. At last,finite element analysis of the tunnel structure and reliability calculation in Xuefengshan tunnel are done in order to provide reference to other underground projects and scientific foundation to reliability of the designing and construction.By the analysis of 3-D non-linear finite element method in the typical region,studying on the modeling of the reliability of the structure and comparing the field data in hand,the paper gets the satisfactory result. The excavation of Xuefengshan tunnel has not basically large deformation, and the entire tunnel is relatively stable. The numerical simulation and monitoring are carried on typical section selected from several categories surrounding rocks. The results show that the support pattern of tunnel is reasonable way to ensure that the tunnel is not of major rock displacement,so as to ensure the overall stability of the tunnel . It can be seen thatβis the largest in the arch feet,followed by lumbar arch,vault minimum,which is basically in consistence with the simulation results. Rock and lining are of great deformation where small-scale collapses occur,and the original design fails to meet the rock overall stability. In subsequence,the new support measures and construction methods has been introduced which are advance small catheter grouting,alteration of support parameter and patterns of excavation. Finally the load-bearing arch has been formed to guarantee that the tunnel is not of major rock displacement,and ensure the overall stability of the tunnel. The analysis of the reliability is feasible and almost embodies the actual stability status of the tunnel. The paramenters and its distribution performance can meet the require. The example confirms this method is effective,practical and feasible to be used in the reliability analysis of the underground structures. The applicability of the method is widely. It can be extended to the reliability analysis of large-sized, complex structure.