Study On The Effects And Safety Of Existing Pipeline Induced By The Tunneling

Large-scale construction of urban rail transit has sharp influence on the existing urban underground environment. Then the accidents of the destruction about underground pipeline often occur due to the metro tunneling. The metro tunneling has disturbed geologic and geotechnical environment, which has changed the loading state of underground pipelines and caused their increasing deformation. It will lead to damage accidents on pipelines when the deformation is overspeed and has exceeding quantity, then the security assessment of the deformation of underground pipeline caused by the metro construction has got a good deal of attention.This paper from the viewpoint of security supervision and evaluation about the underground pipelines caused by tunneling, has studied the analysis method about the deformation of underground pipelines; and researched the change regularity and correlation of the surface subsidence and pipeline deformation during the tunnel excavation by numerical simulation; also proposed the forecasting method of pipeline deformation based on the shell simulation of pipelines.According to inverse calculation, from the monitoring data of pipeline settlement to underground pipeline curvature and stress, this paper analyzes the defects and deficiencies about three- point on same circle calculating the pipeline curvature and introduces the polynomial curve fitting method to calculate the pipeline deformation curvature, also confirms its feasibility.It uses the program of the finite difference about FLAC3D, conducts the 3D Simulation of the deformation which happens under the circumstance aimed at the underground pipelines with different material and zones and loss ratio in different strata during tunnel excavation, and draws the experience formula for the correlation between pipelines and the surface subsidence.Moreover, on the premise of the existing change regularity about soil displacements, it provides the forecasting method of pipeline deformation based on the simulation of pipeline shell, comparing with the elastic and continuous way about bridge structure, presents the accuracy about shell simulation used in pipelines with low rigidity, and also illustrates the feasibility that bridge structure can be used for pipelines with heavy-rigidity.Lastly, synthesizing these above achievements, the safety assessment system about underground pipelines has been integrated and is applied to the practical Engineering-case. Meanwhile, it proves further the effectiveness of both the forecasting method about the shell simulation and the experience formula about the surface subsidence.