The Deformation Characteristics And Long-Term Stability Analysis Of Phyllite Double Tunnel

Twenty-first Century is the era of tunnel engineering and underground space.With the rapid development of transportation in China,a large number of tunnels and underground projects have been built,which have made remarkable achievements.In the western provinces,the development of tunnel and underground space is the urgent need of national development strategy.The ChengLan railway is a new medium speed railway connecting Sichuan and Gansu,which has a lot of problems in tunnel engineering because of the complicated geological environment.One of them is the stability control of time and space effect due to the excavation of deep buried soft rock tunnel.It is common among deep buried soft rock tunnels that diseases like emergence of lining cracking and concrete peeling off the block will appear after the construction and many years' operation,affecting the normal use of the tunnel.Therefore,it is a major subject to study the short-term and long-term deformation and safety control of tunnel structures.At present,there is more study on the deformation and structural stability of the double tunnel and the optimization of the excavation.However,from the perspective of rock rheology,the research of tunnel deformation control technology in the process of long-term deformation is relatively less.In this paper,based on the engineering characteristics of the surrounding rock and the deformation and stress data of the LiuTongZhai tunnel,considering the space and time effect of tunnel excavation,the excavation process and the deformation law of the lining in the 100-year-long operation are analyzed using the numerical simulation software FLAC3D.Combined with the results of numerical simulation,the deformation control technology of tunnel under the action of surrounding rock is studied.The paper mainly includes the following parts:(1)Based on the actual engineering situation,the physical and mechanical properties of the tunnel surrounding rock are obtained,and the actual deformation of the tunnel and the stress of the lining are analyzed based on the measured data of the tunnel deformation and the lining stress;(2)The numerical simulation software FLAC3D was used to simulate the excavation process of the soft rock tunnel,and the load-structure method was used to analyze the safety of the tunnel structure;(3)Based on the basic theory of rock rheology,the creep section of the FLAC3D software is used to simulate the long-term rheological behavior of the tunnel for 100 years with the CPOWER creep model provided in the software.At the same time,the long-term structural stability of the tunnel structure is studied,and the general rule of tunnel deformation and lining stress is obtained;(4)On the basis of summarizing the deformation and stress of tunnel excavation,the influence of the length of excavation steps and different distance between arch and step on the deformation of the tunnel and the stress of the supporting structure is considered.Meanwhile,the proper time to construct secondary lining is discussed to control the deformation of deep buried soft rock tunnel.