Inclined Tunnel Lining Cracks In The Rock Formation Mechanism And Stability Studies

The generating mechanism and stability of cracking lining in tilted stratum is a difficulty and hotspot problem in tunnel construction. However, cracking and leaking tunnels are also in an increase because of operating age, geological conditions, climate, design, and construction and maintain management, etc. Among, the most serious harm is cracking, which can directly affect the operation safety and endurance. Therefore, the producing mechanism of cracking should be analyzed in a deep level so that corresponding repair measurements can be made.Based on domestic and overseas works on this respect, the research result of the lining crack on Shaba Tunnel, Yuhuai Railway is generally analyzed; the strain of lining structure is studied and the Analytical solution to the stress limit of the tunnel lining structure is thus made out. Computed are the crack width of the lining under the pressure of wall rock and its producing sites. The mode I Griffith numeration theor y is applied to measure the influence of cracks on the structure stability. Typical tunnel section is taken to construct the pressure model of tunnel structure so as to proceed numerical simulation analysis. Contrastive analysis is made between simulation results and solutions, according to which corresponding repairing measurements are proposed for lining cracks of different width. Through analysis, the following items can be concluded:1. The geographical condition of ShaBa tunnel is very complicated, and eccentric compression of the tilted stratum is the primarily reasion which leads to lining crack;2. Wall rock in the weak structural plane and tilted stratum slides along the jointed plane. Study about the tilted stratum tunnel lining structure in its limit indicate that prodigious moment is supported by lateral wall, especially is the left wall along the railway, so most crack appear on the left;3. In order to analysis the stability of crack lining, rupture theory is applied. The result indicate that the lining is steadily if the crack is not expand continuous;4. The three-dimensional elastic-plastic numerical simulation can be made by application of FLAC^3D to analyze the stress and displacement rules of each cut section. The result indicate that the basically reason of crack is the extrusion on the lining, which is produced by stratum sliped along the joint plane;5. Generally, the combination of several measurements is used or one special solution is carried out to solve special problem in a certain section of the tunnel. Therefore, the goals of stabilizing the wall rock, strengthening of the lining and insurance of the operation safety can be attained.