岩质隧道施工过程变形时空问题的位移释放系数法

The spatiotemporal effects of deformations of rocky tunnels are significant during the construction. Stress release coefficient method is not applicable to study the deformations of rocky tunnels because of the limited advance knowledge of the quantitative connection between the stress release rate and the parameters associated with the construction process and the surrounding rock properties. In order to investigate spatiotemporal deformations of rocky tunnels during construction, the combination model of Burgers body and Drucker-Prager criterion is applied to characterize the mechanical properties of surrounding rock. The closed-form solutions of tunnel's deformation are derived by using the correspondence principle of elasticity-viscoelasticity and the non-associated flow rule. The displacement release coefficient method is introduced to describe spatiotemporal deformations of the surrounding rock during the construction of rocky tunnels. The maximum short term radial displacement corresponding to plane strain analysis of a tunnel cross section has the similar function formations as the Manh solutions. Moreover, the present solutions reduce to the Park solutions when the time effect is neglected. The correctness and effectiveness of the present solutions are verified by comparing the previous numerical/analytical solutions and the present solutions. Finally, spatiotemporal deformations curves of rocky tunnels, which includes creep characteristic curve of tunnel, radial distribution curve of tunnel's deformation and longitudinal deformation profile of tunnel, are analyzed with considering the effects of different parameters, such as cohesive, internal friction angle, dilation angle and retardation time. The results show that the deformation of tunnel nonlinearly increases with the increase of time and longitudinal distance, but decreases as the depth of surrounding rock increases. The deformation of tunnel is the nonlinear decreasing function of cohesive and internal friction angle as well as the radius of plastic zone. The dilation of rock increases the deformation of tunnel. Besides, the retardation time determines the time history of tunnel's deformation. Effects of incorporated parameters on spatiotemporal deformations of rocky tunnels are consistent with their physical meanings. Displacement release coefficient method successfully describes the spatiotemporal deformations of rocky tunnels, which provides the theoretical guidance for the construction of rocky tunnels.