Research on long-term deformation of tunnel surrounding rock considering the creep characteristics of structural surfaces
In regions where fault fracture zones are developed,the creep deformation of rock structural planes affects tunnel operation safety.First,the finite difference scheme of the Nishihara creep model for rock structural planes was derived.Then,based on the Interface elements in FLAC3D and using a custom constitutive model interface,a dynamic link library for the Nishihara creep model was developed to achieve numerical simulation of creep deformation in the surrounding rock structural planes of tunnels.Subsequent-ly,a validation simulation for the creep of a single rock joint was conducted.Finally,in conjunction with the Qili Village No.1 Tunnel project of the Yichang finished oil transshipment project,the newly developed model was used to simulate the long-term deformation behavior of the tunnel after 1,5,10,and 20 a of opera-tion.The results are as follows:① The creep deformation predicted by the new model is consistent with the analytical solution,with a maximum error of less than 2％;② The numerical calculation results of tunnel surrounding rock deformation have small deviations from field monitoring,proving the reliability of the creep model;③ After tunnel excavation,the surrounding rock deformation is significant,gradually decrea-sing over time,and the displacement tends to stabilize after one year;④ There is no significant damage within 1 to 10 a of tunnel operation,but after 20 a,damage zones concentrated at the tunnel foot appear,and stress concentration occurs at the tunnel foot,indicating that initial support measures at the tunnel foot should be strengthened;⑤ The low-strength and weakly expansive characteristics of the mud-calcareous conglomerate result in significant deformation during tunnel excavation,and under the long-term creep effect of the overlying fault,the tunnel crown continues to deform downward,causing significant tunnel deformation.
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