STRESS ANALYSIS OF INSUFFICIENT THICKNESS RAILWAY TUNNELING LINING DUE TO REPAIR CONSTRUCTURE

Railway tunnel secondary lining insufficient thickness caused by varies factors during construction need reinforce according to current relate regulations when the in-fact thickness less than 70%compare to the design value. We need to define the one time remove area of secondary tunnel lining to ensure the safety construction, and not affect the stability of existing structure. Right and reasonable implementation plan can be determined by calculation, analysis and engineering analogy, et al. For tunnel lining on the poor self-stability Ⅳ and Ⅴ grade surrounding no-layer rock-mass, using analytic calculation and numerical simulation method with 2D GTS(geotechnical and tunnel finite element analytic software),we can obtain the stress characteristics and structure safety factor of tunnel lining under the condition of different removed range on the vault of tunnel lining. The analysis and calculation results imply that the tunnel lining stress is relative large in the vault, side wall and bottom corner and tensile stress appears in the vault zone. The tunnel lining structure is safety when the cut open-window construction of the tunneling vault within 2m2 area for the Ⅳ grade surrounding rock-mass need not consider the reinforcing steel bar effect, but for the V grade surrounding rock-mass, must consider the reinforcing steel bar role.