Research On Composite TBM Support And Subsidence Control Technology

Along with our country the speeding up of urbanization，urban land use and trafficcongestion has become the important factors which restrict the development of the city,urban subway become one of the important means to solve the restriction. Study ofsubway construction and excavation process of underground structural mechanicsbehavior and the impact on the surrounding buildings is very important.This paper takes Chongqing rail transit line6composite TBM excavation for theproject, studies the reasonable compound TBM excavation of tunnel buried depth,internal force of segment lining structure, and through the internal force of structuresdeformation, the main research contents and innovations are as follows:(1)variation of surface subsidence: above the ground along the tunnel axis normaldistribution for both sides, that is far from the tunnel arch of rock, the smaller thedisruption, in line with the law of the formula Parker. Further analysis also get thefollowing conclusions:①rock excavating face of settlement size and distance related to the distance, themore obvious the closer settlement, but as the tunnel face forward, segment andgrouting and other measures to support the application of the surrounding rockdisplacement significantly reduced;(2) According to the numerical simulation results,and refer to the relevant literature that the sandstone reasonable depth is greater than D;③simulation results, in filling in the tunnel, when the TBM through the relativelyweak filling segment reasonable Buried depth should be greater than2D.(2)Composite TBM tunnel excavation for the tube sheet structure. Affect thestructure of the segment force and deofrmation factors are divided into three categories:tube sheet factors include structural stiffness, pipe thickness, the outer radius of the tubesheet, tube sheet width; geological conditions and construction factors, includingassembling way-through the joints with staggered joint, as well as the location of keyblock segment. Analysis the following conclusions:①tube sheet internal force and deformation, and the tube thickness linearrelationship between changes smoothly, within the range of30%; tube sheet width forceon the tube sheet deformation effects: staggered joint assembly for the first increasesand then decreases after becoming on a stable,1.2m slit assembly first increases andthen to smooth; tube-ifn radius of the tube sheet deformation of the intenral forces: ifrst decreases and then increases through the slit assembly staggered joint assembly changessmoothly over a radius of2.5m when the tube sheet The force deformation.②structure of the internal forces and deformation, compared with a large slit assembly,generally10%to20%range; critical fast position adjustment tube sheet in the assemblyprocess produces errors, as well as the tunnel curve adjustment, while its intenral forceschanging the wave shape changes, the deformation of different force ranges, generallyless than20%.(3)When the rock is unstable, there is excavation face collapse, there is thepossibility of subsidence or settlement should be based on the conditions surroundingrock, shield method, and the surrounding environment, the use of pressure, lowering thewater level, grouting, etc. Several ways of maintaining the stability of surrounding rocksurface subsidence caused by shield construction are very complicated and difficult topredict accurately calculate. Therefore shield construction must implement real-timemonitoring and real-time control, in order to keep abreast of ground subsidenceinformation in order to take timely and effective measures in order to control and reducethe loss settlement purposes.(4)beneath the tunnel structure buildings affected by the position of the building isdivided into three categories: a group of pipes in front of the building sheet, a tubedirectly below the building sheet, a group of building the middle segment. Through thesethree positions segment stress analysis, simulation results: different locations segmentstress and deformation properties of subject formation, formation better structure issubjected to the influence of the smaller buildings; different locations tube sheetdeformation force is inconsistent, in front of the building next segment by building agreater impact in the building under less affected. Structural forces in the hole at theexcavation of the more obvious changes in the direction of displacement, excavation portand termination occurs most value. Radial displacement occurs in the most value: vault,arch bottom and port; hoop force deformation occurs at the most basic values:45。，135。，-135°,-45°and the port of; axial displacement occurs at the Central to the differences:Group4tube sheet at0°and180°.