Tunnel Surrounding Rock And Support Structure Interaction

As a tough problem in the tunneling stability, the interaction of the surrounding rock and the supporting structure considers the mechanical properties on the interface as the core issue. Reasonable simulation of the interface has great influences both on the stress distribution of the interface and also on the force and displacement of the surrounding rock and the supporting structure.At present, as a problem of the interaction of the surrounding rock and the supporting structure, one aspect referring the interface of the initial and the secondary support has been well studied, while another aspect is ignored for a long time which refers the interface of the shotcrete and the surrounding rock during the new Austrian method. It is generally considered that the shotcrete and the surrounding rock could work as a stable integrity. Based on the background of a practical project, this paper studies further on the problem referring to the interaction of the tunnel surrounding rock and the initial support and obtains some achievements as following:(1) Deeply studied the mechanical properties of the surrounding rock and supporting structure, established the elastic-plastic finite element model of the interface, and figured out the limit of the tangential shearing referring to the calculation method of the frictional resistance of the rock-embedded pile.(2) The influences of the constraint degree on the interface between the surrounding rock and the initial support were researched. Two different 3D finite element models, one is constraining strictly, another is taking interface friction into account, were established using ABAQUS software to simulate the construction process and obtained the deformation and resistance of the surrounding rock and lining. It was found that the friction on the interface would decrease the resistance of the supporting structure, increase the stress and displacement of the surrounding rock, and even the stress of the surrounding rock and supporting structure up.(3) The finite element analysis also researches on the influence of the design parameters on the stress and displacement of the surrounding rock and the supporting structure containing the length and the distance of the bolt and the thickness of the shotcrete. It shows that lengthening the bolt or thickening the shotcrete separately influent the support structure little. As a result, the design parameters should be comprehensively considered to get an optimization design. (4) Comparing the result of the two finite element models, it was found that the relationship between the stability of the surrounding rock and the resistance of the lining and the embedded depth.(5) After researching on the influence of the friction coefficient on the interaction of the surrounding rock and the supporting structure, it was found that, as the increasing of the friction coefficient, the tangential shearing would increase and the pressure would also increase except the bottom of the arc due to the arching effect.