Research On Settlement Law Of Vertical Gas Pipeline In Metro Tunnel Construction

With the continuous deepening of urban subway tunnel construction,accidents caused by gas pipeline fractures and leaks have occurred frequently,affecting the normal order of the city and the production and life of residents,and also posing a huge threat to the safety of the city.Studying the settlement law of vertical gas pipelines in subway tunnel construction,finding out the decisive factors affecting gas pipelines,reducing or avoiding pipeline damage,fracture and leakage accidents in practical engineering applications are issues that need to be solved urgently.The application of simulation technology can provide an effective means for establishing tunnel construction models.Therefore,in this paper,FLAC3D simulation software is used,with the section between Liaogongzhuang Station and Tiancun Station of Beijing Subway as the background,and the more typical pipe materials are selected as the research object,a three-dimensional finite element model that meets the excavation conditions is established,and the settlement of the gas pipeline is discussed.Laws are of great practical significance for preventing accidents such as gas pipeline fractures and leaks in actual construction projects.First,use FLAC3D software to model the soil and pipelines,choose the linear elastic model as the constitutive model of the gas pipeline,and choose the Mohr-Coulomb model as the constitutive model of the soil.In order to achieve the effect of pre-reinforcement,it is necessary to complete the grouting of the leading small pipe before excavation,which can be achieved by increasing the rock and soil mechanical parameters near the tunnel.A row of monitoring points are arranged at the top and bottom of the pipeline and on the surface to study the settlement law of the pipeline under the vertical intersection of pipe and tunnel.It is concluded that the pipeline settlement curve presents a "V" shape,which is similar to the Peck curve,and the curve change trend is basically the same.The point of maximum settlement value is located directly above the center of the tunnel,conforming to Gaussian distribution.The settlement curves of the pipe top and the pipe bottom almost coincide,and the surface settlement value is larger than the pipeline settlement value.Secondly,using the single variable method,analyze from the three angles of pipe material,pipe diameter and buried depth,and establish models under different working conditions.It is concluded that the settlement curves of steel and cast iron are relatively close,but the settlement changes of PE pipelines are large,especially in the range of-15m<x<15m,the settlement slope changes greatly.When the pipeline is buried deeply,the distance from the axis of the tunnel is closer at this time,and the impact is greater.When the pipe diameter is large,the ability to resist soil disturbance is relatively strong,and the settlement value of the pipeline is small.When the pipe diameter is small,the ability to resist soil disturbance is relatively weak,and the settlement value of the pipeline is relatively large.Changing the size of the wall thickness did not change the settlement value of the pipeline,indicating that the influence of the wall thickness is very small and can be ignored.Figure[16]table[8]reference[55]...