Study On Characteristic Analyse And Controlling Technogy Of Structure Deformation In GPST

Two deep and big work wells need to be built in advance so as to satisfy therequirement of launching and receiving, and the buried section of the tunnel isadopted cut and cover method. But in many cities, work wells are not neededfunctionally in tunnel projects, and the construction of buried sections occupies alarge area of the ground field. As the city and buildings are getting more and morecrowed, the problems of joint construction between ground and tunnel arebecoming more and more serious. GPST is an effective way to solve the aforesaidproblem, which uses shield driving instead of cut and cover of buried section. GPSTcan save about50%ground excavation area, reduce the impact on surroundingenvironment by demolition. Replacing deep and big wells by shallow heading candecrease construction risks and excavation volume, shorten construction period.This article aims at forming a complete set of structure deformation controltechnology in regard to the core problem of structure deformation in theconstruction of ground section tunnel (soil condition depth is less than0.3timestunnel diameter) by scientific approaches of theoretical calculation,3-D simulationand model test etc., which includes the development and application of segmentstabilizer, synchronous grouting control, shield posture control and tunnelanti-floating control. The innovation points of this article are as follows:(1) s per tunnel segments’ mechanical characteristics of ground access section,fixed triangle resistance calculation formula and shell-spring calculation model areproposed. The adaptability of segment load model and calculation model is analyzedfor the first time by segment structure test, and the characteristics of tunnelstructure deformation are put forward.(2) Owing to the behavior of segments prone to deformation upon shield thrustunder extreme shallow overburden, following the study of impact on tunnel stabilityby the rigidity of segmental ring lining, a segment stabilizer which was designed forthe first time to strengthen the rigidity of the entire segmental ring has been verifiedfor its effect after the device’ s implementation.(3) Under multi-mode simulated driving on the largest underground test platformdomestically, the problem of grout filling surrounded by the tunnel in the situation inpartly exposed surface is solved by the innovative research and development of theHE synchronous grouting slurry proportion and pressure injection technology. At thesame time,all these,in conjunction with study on injection port location, andparameters of grouting pressure etc was done to minimize the deformation oftunnel.(4) When the front of shield machines is under super low pressure, GS special mudfor soil improvement, which is researched by863test platform, makes importing andexporting soil normally available. Shield posture control technology guarantees the accuracy of segment assembling; The fine-tuning segment stabilizer, which isresearched and applied for the first time, controls the segment deformationeffectively when taking off from the tail of the shield; Synchronous grouting controland tunnel anti-floating control assure the stability of tunnel.The result of the research applied successfully in the connection of underground andground section of Nanjing metro line6tunnel project, in which the tunnel axiscontrol is within±50mm, ovality is less than0.4%, the floating volume is less than15mm, and the water seepage phenomenon at segment joint does not come up. Allof these support the popularization and application of the new technology in theory,technology and engineering aspects.GPST breakthrough the traditional limits on soil condition. The structure deformationcontrol technology guarantees the quality requirements, which realizes theintegration construction between tunnel and road, offers a brand new solution toplan and design a tunnel route under a special environment. The technology isapplied successfully in the tunnel construction of railway traffic ground accesssection, which is a creation in the world, and the overall construction technologyreaches the international leading level.