Study On The Influence Of Pipeline Leakage On Settlement Of Ground Around Subway Tunnel

In recent years, accidents happened frequently induced by pipeline leakage in subway constructions. Many accidents are caused by the inside water leakage to make the strata saturated, and the mechanics properties of weaken reduced soil.At the same time, the construction disturbance enlarged the deformation of the saturated soil and pipeline leakage. Then they interact with each other to lead to stratum collapsed and pipeline rupture. Based on the methods of theoretical analysis, numerical simulation and engineering examples in subway construction, this text research the effort of the pipeline leakage in the strata distortion in the subway construction.The thesis mainly adopt two phase analysis method. At the first stage, study the pipeline leakage in the soil, apply the numerical simulation to study soil characteristics function,water pressure, the law of location of pipeline leakage to the its effort; At the second stage, study the deformation of soil in subway construction where was leakage of the pipeline, mainly analysis of the impact on the tunnel when the position of the pipeline is different. At last, combined with the example of Tian Jin metro line 2 engineering to make a forecasting analysis about the effort of pipeline leakage in subway construction, to associated the engineering practice with the effort of pipeline leakage in the construction.This paper mainly got the following results:(1)the Ksat decided influence scope of pipeline leakage,with the increase of saturated seepage coefficient,the penetration range increased,the rate of seepage flow increased and the time to reach stable seepage shortened.This text gives the table of the relation between the Ksat and the influence of the pipe leakage.(2)When the pipeline leakage, the extent of leakage of water pressure expand with the increase of the water supply pressure of pipelines.Their corresponding relation is not linear, but curvilinear. In flowing line, the range of leakage doesn't change with the change of the seepage discharge in pipeline area. The change of the seepage discharge only can influence the time between leakage and steady seepage.(3) This text discusses the influence of pipeline leakage on ground deformation under six kinds of position relation between pipeline and tunnel(Pipeline parallel with the tunnel and 3m,2m,1.25m above the tunnel,2m above the tunnel and 2m right in the tunnel,2m above the tunnel and 4m right in the tunnel, vertical with the tunnel and 3m above the tunnel).It mainly analysis of tunnel excavation plastic zone,the change of the ground settlement under the condition of pipeline. The result shows that the closer between tunnel and pipeline, the greater impact on ground deformation. When pipeline located above the tunnel as the most disadvantageous position(4)Based on the simulation and monitoring data of the shield tunneling across pipeline of Tian Jin subway 2 line,it can be found that pipeline leakage will not have influence on tunnel working face under the condition that the pipeline are 8.4m apart from the tunnel; but tunnel construction will have serious influence on the pipeline that the soil beside the pipeline will distort seriously When the tunnel is excavated under the condition the pipeline leaks stably, the settlement of the bottom of pipeline can be 0.49m. In engineering program, pipeline leak did not occur, so the surface subsidence of numerical simulation was consistent with the monitoring. If the monitoring data increased obviously in the construction, it may be induced by the pipeline leakage. The numerical simulation of ground deformation caused by pipeline leakage was to forecast the possible dangers, so we can make the monitoring program in the project and protection of pipelines in advance.