科研之友
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摘要
Research purposes: Some serious damages, such as joint dislocation, transfinite deformation, segment breakage and cracks, leakage of joints and bolt holes, have been found in the metro shield tunnel, which induced by anti-floating anchor high-pressure grouting next to metro shield tunnel. It threatens metro operation and structural safety of tunnel. Based on the foundation pit construction process, tunnel damage status quo and monitoring data in actual engineering cases, this paper analyzes the causes of tunnel rising and damage by means of numerical simulation, and puts forward an aerial structure and light backfill scheme above the tunnel, which can provide reference for similar projects. Research conclusions:(1) The large area of anti-floating anchor high-pressure grouting in the basement of the foundation pit is the main reason for the rise of the tunnel. The heavy reduction of the soil layer above the tunnel caused by the rise of the groundwater level and the softening and expansion of the strongly weathered silty mudstone reduce the resistance of the soil layer above the tunnel.(2) Longitudinal uneven upwelling and increase of tunnel lateral pressure caused by grouting lead to ring radial stagger and elliptical deformation of the tunnel, and the excessive deformation is the direct cause of the crack of the side wall of the tunnel piece, the leakage of joints and bolt holes. (3) In view of the tunnel cracking, leakage and ellipticity deformation, the corresponding treatment measures are proposed. (4) The backfilling scheme of "aerial structure + light EPS board", corresponding construction procedure and key points of EPS board construction are put forward. The measured results showed that the metro protection scheme could control the tunnel settlement to 9.1 mm. (5) The research results can be used as a reference for similar shield tunnel overburden engineering.
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