Study On Weak Surrounding Rock’s Stability Of Large Sections

Series of large cross section tunnel appeared in our country with the rapiddevelopment of high-speed railway and the constructions needs of passenger dedicatedline, its excavation of the cross section area above100square meters on average,construction of large cross-section tunnel is difficult in the soft and broken geologicalconditions.Take Mount Taiyue railway tunnel project in Shan-xi Province as the backgroundin the paper, the paper expounds the main factors affect the stability of surrounding rockand its theory. Analyzing the excavation methods of the tunnel, the supportingparameters and supporting patterns, choosing similar material according to the nature ofthe surrounding rock to do the simulation experiment, get the elastic modulus (E)andPoisson’s ratio (μ)of the argillaceous by the analysis of the elastic stage of the testspecimens, obtained bulk modulus and shear modulus of the surrounding rockaccording to the formulaK K=E/3(1-2μ) and the formula G=E/2(1+μ),offer acalculation basis for the numerical simulation of the tunnel excavation in the fourthchapter.Excavation the tunnel construction based on the single side heading method andthe steps method to simulate the process of the tunnel excavation, doing a numericalanalysis the surrounding rock and the supporting structure in site of the tunnel. Do atwo-dimensional numerical simulation by FLAC software, combining with thecharacteristics of domestic and foreign research on tunnel, and the present situation ofthe tunnel construction methods, simulating the mount Taiyue tunnel with single sideheading method construction and steps method, which have the same cross section areaand the same geological conditions. Monitoring the key parts in the process of tunnelexcavation, the results show that the deformation is the largest after the excavation ofthe upper right for the construction of single side heading method, the amount ofdisplacements at the bottom of the vault and arch take up the total respectively97.6%and93.4%, the maximum compressive stress distribute in both sides of the tunnel wall,the stress concentration is prone to happen on the arch of the foot in the tunnel, for threesteps method, the largest vertical displacement concentrates on the vault and archbottom of the tunnel, the maximum horizontal displacement concentrates in the wall on the both sides of the arch, large vertical displacement and horizontal take place duringthe process of excavation. Compared the lateral deformation, the vertical deformationand the stress of surrounding rock with two kinds different construction methods, thesingle side heading method is more conducive to the stability of the surrounding rockwhen excavated from the perspective of the size of structure deformation and stress.