Research On Characteristics Of Situ Stress And Surrounding Rock Classification In Erlang Mountain Tunnel In Yakang Expressway

In-Situ Stress will have a significant impact on tunnel design and construction,which is affected by many factors such as topography and geological structure of the region.At this stage,borehole stress measurements are the most effective means to acquire the GEO-stress.But due to the restrictions by terrain,technical and financial,stress drill on a large range using the borehole measurements is not realistic.Therefore,it can be obtained by computer inversion stress of the region.The other hand,the data show that,the surrounding rock classification methods used frequently is poor adaptability for deep and over-long tunnel under complicated geological condition,which is not conducive to guiding and supporting of tunnel construction.So establishing a method can be better adapted to judgement of surrounding rock classification under complicated geological condition is considerable significance.This article mainly takes Erlang mountain tunnel of YaKang expressway as example,the research results are as follows:1.Analysis on environment of engineering geology of Erlang mountain tunnel.For geographical position,Erlang mountain tunnel located at the mid-high mountains region of the junction of Sichuan basin and the Qinghai-Tibet plateau.For geological structures,it located in the side of the Chinese famous junction of three tectonic system of three forks in the west.The topography is magnificent,undulating,ravines are clustered,the geological structure is complex,the fault joint develops,and the rock formation is exposed completely.2.Based on the coupling of CATIA and FLAC3D,wrote the CATIA-FLAC3D interface program.Taken CATIA as the modeling platform,established three dimensional geologic model of the Erlang mountain tunnel and imported into FLAC3D by the interface program and made analysis simulation.According to the principle of superposition of elastic mechanics,used the 6 types of boundary conditions to simulate the geostatic stress and tectonic stress for computing stress component,and acquired fitting formula of the initial GEO-stress field in the region the through the regression analysis with measured stress components.In result,the maximum principal stress of Erlang mountain tunnel is 56.61Mpa,these the high or sky-high stress region accounted for 58.47%of a total length of the tunnel.3.Based on the initial stress of tunnel acquired from inversion calculation,predicted the strength of rock burst and large deformations of the surrounding rock of the tunnel axis through the geological synthesis method and stress intensity ratio method.In result,rock burst region accounted for 79.7%of a total length of the Erlang mountain tunnel.The majority rock burst is the slight rock burst.The local region can be with existence of medium and strong rock burst.The region without the occurrence of large deformation accounted for 91.4%of a total length of the tunnel.The region of large deformation only accounted for 8.6%,and the majority is slight deformation.The local region can be with existence of medium and strong large deformation4.At this stage,due to BQ method used commonly cannot be better adapt to the tunnel surrounding rock level judge of deep and over-long tunnel under complex geological conditions.This article established a method can be better meet to the construction phase of the Erlang mountain tunnel of YaKang expressway based on variety standards and BQ method,which was named as BQsg surrounding rock grading method.This method taken the nature of qualitative and quantitative into consideration,and determined the level of surrounding rock progressively and Hierarchically.The method is applied to the actual to examine.