Study On Mechanical Behavior And Close-Spaced Subarea Of Adjacent Shield Tunnel

In intermediate sections which the line of interval tunnel is changed from upper and lower overlapping to parallel, the stratigraphic effect and mechanical behavior of structure caused by construction is very complicated. When the impact on each other is significant,the construction of the tunnel built after will lead to the rock around the tunnel built before be relax and produce bias and deflection displacement of structure, and may even have the fracture damage of tunnel structure and the failure slip of rock,.which cause much difficulty about structural safety and the subsidence control of the formation during the construction period and the operation. Therefore, the correct analysis of the structure form of overlapping tunnel and the stratigraphic effect and mechanical behavior of structure and the interaction of the two holes caused by construction in the intermediate sections ,and on the base to choose a reasonable construction measures, is a very important technical issues.Based on the old-Eastern close-spaced section shield tunnel interval in the Shenzhen Metro Line 3,this paper uses FEM as the research meas to systematically study the model of two shield tunnel in four different Relative position: overlapping in the up and down, overlapping transition section (-45°and 45°), horizontal parallel section,and study the influence rules of the stratigraphic displacement, ground displacement ,the internal force of the structure in different distance and construction sequence, but also partition close-spaced section shield tunnel based on the criteria of structure strength,and advance some measures of close-spaced construction. Main concluded: From the perspective of structural moments, the construction sequence which construct upper tunnel first is better than that construct lower tunnel first.The borderline of strong and weak effect subarea is like an opened bag.the greater the buried depth, the smaller the mouth of the bag which is much nearly closed. The smaller the buried depth, the bigger the mouth of the bag, which isn't much nearly closed.According to the object of action, this paper puts forward three different measures, namely the countermeasures of the existing tunnel (or the tunnel building before), the countermeasures of new(or after) building tunnel, and the countermeasures of middle strata.