Study On Influence And Control Of A Tunnel Construction In Chongqing Rail Transit To Underground Pipeline

For the complicated engineering problems at this stage: the influence of tunnel excavation on underground pipelines is currently a hot and difficult point.The height of the terrain in Chongqing is large,and the tunnel excavation is prone to occur very close to the underground pipelines.Improper handling can result in pipeline damage and even engineering accidents.By controlling the single variable principle and relying on the five-standard Chen jia ping station project of the Chongqing rail transit loop,the influence of underground tunnel excavation on the adjacent underground sewage pipelines and control standards were studied.The main conclusions are as follows:(1)Sandstone mudstones are widely distributed and exposed in Chongqing,and the strength and deformation characteristics of rock masses in soft and hard layers are more complex and changeable.By changing the elastic modulus,cohesion,internal friction angle,the relative position of the pipeline and the tunnel,the depth of the pipeline,the parameters of the pipeline itself and the excavation step,etc.,It is found that in the case of parallel tunnels and underground pipelines,the change of the elastic modulus of the surrounding rock has the greatest influence on the vertical displacement of the pipeline,followed by the cohesion force,and the influence of the internal friction angle is the smallest;The settlement at the distance L=0m from the tunnel axis is the largest,and the tunnel excavation influences the underground pipeline approximately twice the net tunnel width.Within this range,it is possible to reduce the tunnel excavation,advance support and other methods to control the pipeline settlement;The better the surrounding rock,the smaller the subsidence of underground pipelines.(2)Under the same conditions,It was found that under the vertical conditions of tunnels and underground pipelines,with the increase of the elastic modulus,cohesion and internal friction angle of surrounding rock,the vertical displacement of underground pipelines gradually decreases,and the settlement curve shows a V-shaped change,and There is little change in the settlement value at ±3m in the tunnel axis;The smaller the distance between the pipeline and the top of the hole,the greater the settlement of the pipeline will increase;When the digging footage is not the same,the maximum settlement of the pipeline occurs at the location of the tunnel axisand decreases from the middle of the axis to the two sides.The larger the excavation footage,the faster the vertical displacement of the underground pipeline increases.(3)Analyze the monitoring data from the example of Chenjiaping station and numerically simulate the subsidence values of the underground pipelines and compare them.It is concluded that the surface subsidence monitoring value is slightly smaller than the numerical simulation subsidence value,and the tunnel dome settlement monitoring value is greater than the numerical simulation subsidence value;It is concluded that the monitoring value of surface subsidence is closest to the numerical simulation settlement value.If the subsidence value cannot be directly monitored due to site constraints during the construction process,subsidence monitoring values can be used to replace subsidence values of underground pipelines,but the warning value of subsurface pipelines should be slightly less than Direct monitoring of underground pipelines when the warning value.(4)Through statistical analysis and combination of project practice,it is proposed that the settlement control of the sewer line in Chongqing is12mm;Summing up some protective measures for preventing the destruction of underground pipelines,two measures can be adopted for the control of underground pipelines.One is to relocate the pipelines,and the other is to reduce the excavation footage,reinforcement of surrounding rocks,advance support and other methods,making pipelines Settlement is within the control range.