The Reaearch Of Large Deformation Mechanism Of Tunnel In Erosed Granite Area

Granite altered rock refers to the original rock with in late invading granite hydrothermal action after the formation of the altered rock. Granite altered with rock mass strength low, among them the montmorillonite altered rock is bibulous expansion characteristics, can make structure closely altered rock disintegration. And later in the band of granite invades altered by multiple tectonic function and magma intrusion influence, rock crack development, rock joints, a loose broken rock gravel breccia and silt shape, stability is poor. This geological phenomenon at home and abroad is relatively rare in engineering construction, the construction of similar projects currently less experience of granite altered rock distribution rule and engineering properties research, the altered rock area of engineering design are also irregular to follow. This thesis studies on object to the Beigang tunnel of Luo-Zhan line between Wuzhou-cenxi, the tunnel is located in altered granite area, with weak surrounding rock band and food in the middle expansive, ground water development. In tunnel construction is not only appeared tunnel side-wall deformation, there appear a large number of the gushing water and sand, partial collapse of the formation of cavity, surface formation of collapse pit and the construction of the tunnel was forced to comprehensively stop, change the design.This thesis by gathering of altered rocks related information to understand the Beigang tunnel geological conditions and construction deformation and field sampling of conventional test and static triaxial test, small direct shear tests, large direct shear tests and swelling tests to determine the alteration rock physical mechanics characteristics. FLAC3D in the two Mohr-coulomb model and SS model inversion method of Beigang tunnel surrounding rock under rock mass parameters inversion, the results and test results contrasted analysis and validation. Following conclusions and achievements:1 Beigang tunnel erosion types of magmatic hydrothermal alteration, alteration of generating a lot of hydrophilic strong montmorillonite, chlorite and clay minerals in altered rocks moisture content of high rock strength reduction, water swelling disintegration;2 The Mohr-coulomb model ideal elastoplasticity inversion's parameters of surrounding rock does not tally with the actual situation, SS soften model all inversion results accordant with the actual situation, namely Beigang tunnel altered rock has obvious parameters damage characteristics;3 With Beigang tunnel DK462+545 section for calculation model, using FLAC3D calculation discussion on contact angle and distance to the tunnel construction deformation characteristics of law on the basis of the generalized model; 4 Three typical characteristics of rock under different retaining to the numerical calculation of granite alteration zone of tunnel construction control measures, According to rock convergence for surrounding rock displacement curve characteristics and engineering control requirements, you can select a different retaining strength, ensuring the safety of surrounding rock and avoid further strain softening and properties of weakening.