Study On The Influence Degree Of Adjacent Construction Of Three Parralell Shield Tunnels

With the boost of economy, the demand of infrastructure is increasing, especially in means of transportation. Lots of cases of adjacent construction in tunnel and underground project had appeared in the perfection of traffic net. Tradition theory is based on the mechanical behaviors of single cavern in semi-infinite or infinite medium, while most of the researches on adjacent construction are based on experience and case study with a little systematic study. It seems from actual design norms in China that such researches are mainly based on non-influential zone of elastic solution and empirical value, or separate model, which lack of necessary and sufficiency theoretical analysis. For framing norms and guides, it's necessary to do some research on the theory.This dissertation carried out a study on the particularity and universality of the adjacent construction which depends on the project of R413 in the ninth line of shanghai track traffic, by using the methods of investigation and study, numerical analysis, model test, in-situ test and analog.The following achievement and outcome was gained:1. This dissertation develops the theory of literature [1] by defining geometric adjacent degree and adjacent influence degree, putting forward the expressions of adjacent influence degree and adjacent influence subzone and limiting the adjacent influence subzone to normal procedure measures.2. This dissertation researches coherent threshold of different influence degrees and subzones based on the criterion of Land subsidence, and puts forward the criterion expression of reinforced concrete strength and coherent threshold. Ratio threshold of strength and coherent threshold based on the concept of influence grade are given. And so is the using of the ratio of dynamic and static load as the strength criterion of analyzing dynamic load of train acts on the tunnel.3. In this dissertation, according to the definitions of adjacent influence degree and influence subzone, the coefficient of the geometric adjacent degreeα_0ij, the one influence by depthα_4ij, and the synthesis coefficient K_ij are studied by using statistical mechanics, with the base of the land displacement criterion, strength criterion and the criterion of ratio of dynamic and static load. Therefore the influence subzones based on ration of depth (H/D) with geometric adjacent degree A, or the stress ratio (R_b/σ₀) are put forward.4. By the use of 2D and 3D numerical simulation, centrifugal model experiment and in-situ test, the stress field, displacement field and the regularity of inner force are studied. And the control key and mechanics principles are indicated. Therefore, the classifying process of parameter in shield construction and classifying of countermeasures that correspond with the conventional adjacent degree are studied.5. In this dissertation, the driving of the shield is simulated by the method of dead and live element and the stiffness and load migration. The filling and hardening of inert fluid are simulated by the use of weak solid mass and gradually increasing the modulus of elasticity. And the pressure of injecting and the dissipation of the pressure are simulated by the expansion and contraction effect brought by temperature. The loss of soil in the ground in shield driving is simulated by the method of injecting and releasing certain amount of water contained in pockets. A three-dimensional finite element model is established in this dissertation to simulate the movement of the wheel load when the trains are vis-a-vis with each other, and the dynamic analysis with the interaction of solid and stricter is realized. This dissertation also uses the influence line method greatly to analyze the mechanical behavior of adjacent construction, and establishes a simplified model in plane based on the dynamic earth pressure of vault.6. Some conclusions about the shield tunnel cases and the universality study of three-pore tunnel were gained.This dissertation mainly deal with the research on synchronous adjacent situation of three parallel tunnel that constructed by shield, which geological conditions are similar with the project of R413. And in the aspect of influencing factors, only the influence of geometric adjacent degree and depth are researched. Much more work should be done type by type and factor by factor because of the great numbers of adjacent construction types and influence factors. For framing norms and guides to direct the design, construction and management, the index system of influencing subzone should be established and perfected as soon as possible by putting the emphasis on a few adjacent tunnel types that are in common use.