Abstract
Structure form, steel bar and service time were considered to be the main factors of the tunnel disease state, based on the disease inspection results of subway tunnels in Beijing. The conclusion indicated that the diseases of shield tunnel such as ovalization of tunnel cross section, lining cracks, crushing and dislocation of duct pieces and water leakage were caused by the deformation of segment joints. Lining crack was the main disease form in monolithic tunnel. The width and depth of cracks were greatly influenced by tunnel operation time and had the characteristics of discreteness and random. Steel bar used in concrete lining could significantly enhance safety of tunnel structures. Water leakage in subway tunnel was influenced by rainfall and usually could be observed at the gaps of tunnel structures, such as bolt holes and segment joint of shield tunnel or the construction joints, deformation joints and lining cracks of monolithic tunnel. The most lining cavities were found located at the vault and the cavity shape was similar to strip, square or oval with lining cracking nearby. The carbonation depth of lining concrete was proportional to tunnel operation time and its value and speed at ballast bed was most, sidewall less and vault least. It is hoped that the results can provide some reference for the disease law analysis and treatment of urban tunnel.
Highlights
It's shown by the daily inspection results and maintenance work that the structural defections are all over the subway tunnels in service
The results show that the damage state of subway tunnel is greatly affected by the structure form of tunnel, the proximity construction, service time, concrete reinforcement and the location of measurement points
Based on the on-site inspection results, this paper analyzes the disease status of Beijing subway tunnels in service and draws the following conclusions: (1) Deformation of segment joints is an important cause of diseases of shield tunnels
Summary
It's shown by the daily inspection results and maintenance work that the structural defections are all over the subway tunnels in service. Zhang [1] based on the survey results of Nanjing Subway, classified the subway tunnel defections into longitudinal settlement, crack, seepage and ballast bed separation. Ye [2] analyzed the causes of defections based on the monitoring data of longitudinal unequal settlement in the tunnel of Shanghai Subway Line 1. Based on the special inspection data of typical lines of Beijing Subway, the main disease states of two types of tunnels are analyzed. The diseases of subway tunnels are divided into over-limit deformation of shield tunnel, lining damage, water leakage, and ballast bed damage. The results show that the damage state of subway tunnel is greatly affected by the structure form of tunnel, the proximity construction, service time, concrete reinforcement and the location of measurement points. The results show that the damage state of subway tunnel in service should be considered as an important factor in the selection of construction methods during construction period
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