Study On Influence Of Shield Construction On LNG Pipeline And Construction Optimization Control

In this paper,the influence of underground pipelines and the control of construction parameters during the construction of subway shield are studied.The combination of theoretical analysis and numerical simulation was used to analyze the contact between pipeline and soil and the deformation and force of the pipeline.The multi-output support vector regression algorithm was used to optimize the construction parameters during the tunneling process.The main research contents and results are as follows:(1)The two-stage method was used to analyze the normal contact between underground pipelines and soil.The two-stage calculation process is simplified,and the beam-spring-stratigraphic model is proposed.The two-stage method is simplified into a model,and the results of the beam-spring-stratigraphic model are compared with the results of the two-stage method.The results show that the calculation error is within a reasonable range,which proves the rationality of the beam-spring-soil model.Finally,a contact unit was established to analyze the tangential contact between the pipeline and the soil.(2)Using the Winkel elastic foundation hypothesis,the deformation of the pipeline is solved when the shield tunnel passes vertically through the pipeline.Firstly,the hypothesis that the soil foundation coefficient k is non-uniform around the pipeline during tunnel excavation is proposed.The differential equation of the force balance of the pipeline micro-segment is established.The numerical solution of the differential equation is solved by the Galerkin weighted residual method.And use the Maple software to compile the corresponding calculation program.Finally,a case study is carried out to verify the rationality of the method and hypothesis.(3)Using MIDAS GTS NX software,the three-dimensional numerical simulation of the natural gas pipeline under the forest-ocean section of Xiamen Rail Transit Line 3 was carried out.The variation of surface subsidence and pipeline stress and deformation during shield tunneling was analyzed.(4)Based on the actual project of the natural gas pipeline in the forest-ocean section of Xiamen Rail Transit Line 3,the evolutionary multi-output support vector regression algorithm is used to establish the prediction model,and the relationship model between the shield construction parameters and pipeline stress and surface settlement is established.The shield construction parameters were optimized by using Immune Clone Selection Algrithm combined with safety evaluation indicators,and the optimized construction parameters were given.