Research And Application Of The New Half-Rigidity Shell Bolting Shotcrete Support System In Soft Rock Tunnels

The underground support structure can benefit from ground shell bracket for its lightness and high stability. In this paper, a new kind of structure of underground shell bolting lining was designed which was based the analysis of the shell structures mechanics principle. The rock-support theory of interaction and the support of soft-rock tunnels were studied.Shell bolting spray layer lining is composed of the grid structure of reinforcing bar and spurt concrete. The grid structure which is used in the board shell structure which is formed of reinforcing bar welded in the ground, the surface of which forms a net of reinforcing bar, can support the tunnels rock surface. Every structure's two sides weld connecting plate with bolt holes, and every bracket which has certain flexible ability is packed by several components and is connected by the bolts, while layer of wooden blocked is inserted between connection, which make support have compressibility This kind of support has two obvious characteristics: first, concrete have been surrounded in the numerous little span arch shell, while the tensile stress and shear stress of spray layer are weakened obviously and its compression strength is used sufficiently. So the support's ability is higher than common distributed steel spay layer; second, when shell bolting is formed after spraying concrete, compressive connection make shell bolting liner have certain yielding ability. New liner not only modifies with rock but also supplies stronger holding power to rocks, which also is regarded as the permanent support structure of soft-rock tunnel, the tunnel of dynamic pressure and so on.The new theory of local weak support was put forward in the paper on the basis of anchor spray support principle. The mechanics characteristic of the half rigidity reinforced shell bolting and shotcrete support was studied. The structure's internal force was analyzed and calculated .The formulas of internal force, displacement stress was deduced according to the general mechanics theory of the ringent cylindrical shell. The model experiment was done by relying on the industrial test and the distortion, destruct shape, developmental rule of the supporting system was examined while the stress and strain distributing rule and also the ultimate load were obtained. The calculative model of finite element numerical simulation with computer was established on base of combing the theory analysis with the experimental result. As the result of the numerical calculation the study on the structure was supplementary verified finally. The result of different calculation methods was compared and the otherness was making for the optimizing of the design project. At 1ast, the conclusion of numerical calculations proved that ANSYS program is reasonable and creditable.With combination by typical engineering, the construct technical request and the process criterion were established. It was compared to other supporting method that used commonly in soft rock tunnels by locale watching and testing, the technique, economic contrast of the typical tunnel with shell support was completed and the social benefit was evaluated.