Analysis of deformation and stress characteristics of highway tunnels above mined-out regions

It is of challenge and emergent problems for hazardous assessment and treatment technology for the mined-out regions under the highway with bridges and tunnels. Based on the Fanshuigou bridge-Shipogou tunnel project which is through the mined-out regions in Liulin section of Qingdao-Yinchuan highway, the three- dimensional computation models have been built by using the MIDAS/GTS finite element program; and numerical analyses of the ground deformation response, and tunnel lining and bridge structural deformation as well as their structural forces using FLAC3D are performed. The processes are generated in the step-by-step mining region for treatment after mining coal in Tongde area. And then, the double-layered Shipogou tunnel is excavated and Fanshuigou bridge is constructed. The surface deformations under different working conditions have been revealed; and the ground subsidence basin characteristics and the central subsidence position have been determined. Also, the deformations and forces of key bearing parts of tunnel lining and bridge have also been predicted. Based on the hyperbolic model and grey model, a new combined weighting model of subsidence for highway tunnel through mine-out regions is built with the technique of minimal absolute values of errors, in which the weighting average is calculated with MATLAB. The engineering measurement results show that the predicted error with combining weighting model is reduced; and the acceptable results are obtained. The above-mentioned results have important theoretical meaning for guiding the practice of grouting mined-out regions and supporting of tunnels and bridges to meet the requirements of strength, stiffness and stability of tunnels and bridge structures.