Surrounding Rock Pressure Characteristics And The Deformation Shape Numerical Calculation Of Shallow Large Section Tunnel

With the growth of traffic pressure in recent years, a large number of high-gradehighways have been constructed in domestic and therein the tunnel engineeringtechnology developed toward large section flat direction. Large section tunnel structuredetermines that the form of this tunnel construction is of great difficulty and highsecurity risk with research and testing stage, so there is little design and constructionexperience to draw on and a number of technical issues are to be resolved. In this paper,by theoretical analysis and numerical simulation methods, in order to optimize thedesign and construction, I will do some research on the shallow large cross-sectiontunnel surrounding rock pressure characteristics and deformed shape.First, expound the classification of the rock pressure. Analysis of the change ofsurrounding rock initial stress field, the stress field after excavation and the stress fieldafter supporting, pinpoint the mechanism of the surrounding rock pressure andsummarize the main influencing factors of the rock pressure. Summarize thedevelopment, current situation and the application scope of the calculation theoryrelated to surrounding rock stress. In this paper, using the elastic-plastic theory and thefinite element software Midas to establish planar model to calculate the stress anddisplacement of shallow large section tunnel surrounding rock and the bendingmoment, axial force and shear force of the supporting structure. Comparative analysisof the characteristics of the changes in surrounding rock pressure and displacementdistribution under different cross section sizes, different surrounding rock levels anddifferent two-hole pitch conditions.The results show that there is a high stress area between the large section tunnel sidewall and the joint between it and the inverted arch and there is stress concentrationphenomenon; the total deformed trend of the surrounding rock is vault sink, sidewallopen on both sides, and the inverted arch extrudes to the cave. For the neighborhoodtunnel, the stress concentrated and excessive deformation parts are: the connection areabetween sidewall and inverted arch, the vault、on the side of the rock pillar in themiddle of the sidewall of small spacing tunnels. Numerical results can be moredirect-viewing in indicating the distribution rules and characteristics of the stress anddeformation of the surrounding rock pressure, which contributes to correctlyunderstanding and analyzing the shallow large section tunnel retaining structure force.And then can provide a scientific basis for the rational design of large cross sectiontunnel support parameters.