Study On The Freezing Damage Mechanism And Control Technology Of The Railway Tunnel In Cold Region

Freezing damage is generally exists in tunnel in cold region, which influence the using performance of the structure and is a focus and difficult issue puzzling the engineering. Aiming on the freezing damage in tunnel in cold region, relying on Lijiawan 2# Tunnel and Jundushan Tunnel the paper analyzes the factors of freezing damage and the influence of frost heave on surrounding rock and lining structure by means of field research and theoretical analysis and numerical simulation. And finally proposes new improvement methods for the cold damage. The main research contents are as follows:(1) Analysis on the appearances and factors of freezing damage in tunnel. The common forms of the freezing damage in tunnel include: leakage in lining, ice on the lining, cracks caused by freezing, mud-pumping of basement, swelling caused by frost heave,cracks on portal, thaw slumping at the portal, blocking of the drainage system. Analyze the factors of freezing damage from the temperature, water, surrounding rock and the design and construction defects. Also study the surrounding rock and lining’s characters of frost heave in situation of freezing and thawing cycle.(2) Research on principle of freezing damage of the lining structure. Cracks on lining are related to the volume expansion when water freeze into ice. Homogeneous pore water surrounding rock and constant thickness frozen aquifer rock is used as the frost heave model to calculate the frost heave force. The tension crack, slab staggering and crushing will appear when the frost heave force acted on the lining exceeds the tensile strength, shearing resistance, or compressive strength of the conctet.(3) Researched the distribution of temperature field in tunnel. As an example of LiJiaWan No.2 tunnel,by analysis simulation of temperature field distribute characteristics with finite element software, known that the distribution of frozen surface along the longitudinal tunnel in 3D is roughly horn mouth shape, and applied 5cm rigid polyurethane insulation layer can ease the growth of the frozen circle and decreases the frozen depth of surrounding rock.(4) Proposed prevention and treatment measures of tunnel freezing damage in cold region. To remediate freeze injury should be based of manage water, taking into account of heat preservation, reinforce of surrounding rock and lining, improve the quality of design and construction,taking the comprehensive treatment scheme of combine electric heating and heat insulation layer and drainage blind tube can effectively control the leakage of ice diseases in Jundushan tunnel, the new control measures of the basement of surrounding rock grouting reinforcement can improve the surrounding rock condition, improve the bearing capacity of surrounding rock.