| The subway tunnel underpasses a gas pipline of sub-high presure (Φ508×7.9, pressure 1.6 MPa) located in fault fracture zone in the mileage of K9+105-K9+135 (fracture zone), at Shang (Shangmeilin Station)-Min (Minle Station) Section of StageⅡof Shenzhen Metro Line 4. The pileline buried in the artificial filled solid (rock) zone, about the depth of 3.5m to the surface,16.0m to the tunnel. In addition, a natural-gas pipeline (Φ600) of Guangdong Dapeng Company, two water pipes (DN1100, DN200), a power pipeline (Φ329.9×6.4) and underground cables exit nearby. How to control the surrounding rock deformation & ground settlement, and reduce the loss of groundwater effectively, is the key way to ensure the safety of the gas pipeline and also the prerequisite for the smooth'progress of the project for a tunnel construction in week & water-rich strata.The control of the surrounding rock deformation & ground settlement, the loss of groundwater and the pipeline protection technologies are researched and analysed in this paper based on the project of Stage II of Shenzhen Metro Line 4 through theoretical analysis, numerical simulation (FLAC3D), on-site gas pipe testing of stress monitoring and settlement. Some achievments obtained are as follows:(1) The simulation results of rock deformation and displacement of settlement conducted by using the finite element software (FLAC3D) show that:the advanced support of pipe roof and the small duct grouting can well control the deformation and the settlement, as well the partition-water-seal can seal the groundwater off the tunnel area, which is conducive to the stability of tunnel face and the construction of continuity.(2) As the site is located in the fault zone with rich groundwater and high water pressure, the effect is limited if the sealing measure taken only. Advanced drilling-wate-discharge in the face can reduce the water pressure effectively, reveal the conditions of the strata 15-20m in front as well. The pipe with whole body perforated and double geotextile filters packed can allow the flow of the groundwater while keep the sediment off.(3) For the protection of subhigh-pressure gas pipeline, besides the means of the control of rock deformation and settlement taken, the gas pipe itself is considered, the weak parts are reinforced, combining with the upper load reduction of the pipe. In the process of tunnel construction, long-term monitor of the pipe is conducted to record the settlement while a new technique of non-destructive stress measurement is introducd to inspect the pipe stress situation. This technique of pipeline detection can provide reference for the similar projects in future. |
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