Research On Segment Floating And Airport Tubing Settlement Induced By Shield Tunneling With Small Turning Radius

During the excavation of the airport maglev shield tunnel,the airport runway and underground oil pipes will be disturbed,and in severe cases,the process of the excavation will affect the safe operation of the airport and cause significant economic losses.However,when the shield machine is excavating in the curved section,the influence on the segment and the disturbance of the underground tubing is more significant than that in the straight section.Therefore,it is essential to clarify the floating of segments and the deformation and disturbance effects of underground oil pipes caused by shield tunnel excavation in the maglev curve section of the airport.The theoretical calculation,numerical simulation,and on-site monitoring methods are mainly adopted in this thesis to study the construction risk factors and risk events of shield tunnel excavation face support force,segment floating,and underground tubing settlement.The specific research contents and results are as follows:(1)Based on the theoretical model of the silo,a prism-like balance model for the support force of the excavation face in the curvilinear section is proposed.The limit equilibrium equation is established for the excavation surface,and the limit support force is solved.The distribution law of soil extrusion force and rupture angle in the process of shield tunneling in the curved section is obtained,and Matlab programming is used to solve the rupture angle by iterative trial algorithm;(2)Through the analysis of the floating mechanism of the segment,the main factors affecting the floating of the segment are obtained,and the corresponding measures to control the floating of the segment are proposed.Measures such as controlling the time and orientation of the synchronous grouting point,timely adopting the secondary grouting,controlling the reasonable driving speed,dynamically adjusting the shield tunneling parameters according to the feedback of on-site construction monitoring data,are adopted to reduce the impact on segment floating;(3)Relying on the Changsha maglev east extension line to connect to the T3 terminal project,the energy variation method combined with Mindlin solution and mirror method is used to derive the settlement formula of the underground oil pipe caused by shield tunnel excavation the in the curved section under the influence of additional thrust of shield excavation cutter head,shield shell frictional resistance,additional grouting pressure of shield tail,formation loss and other factors,under the influence of the excavation of the shield tunnel in the curved section.The influence of each parameter is simulated by FLAC3 D,and the ultimate bearing capacity and allowable deformation limit of the underground tubing are analyzed.Pipeline sensitivity analysis was further conducted.The construction suggestions to guide the on-site construction to ensure the safety of the underground oil pipe are put forward;(4)By comparing with the actual engineering monitoring data,the applicability of the theoretical calculation formula and the law obtained by numerical simulation are analyzed and verified.Suggestions and construction control technical measures for strengthening the on-site monitoring and distribution of underground tubing inside the curve section are put forward.