Deformation Monitoring Of Water-rich Tuff Soft Rock Tunnel During Construction And Numerical Simulation

With the development of China’s high-speed railway construction,the project builders have encountered some difficulties and challenges while achieving many achievements,which cannot be avoided in the process of building a mountain tunnel.In the current construction of large-scale mountain tunnels in China,the design and construction problems of weak surrounding rock tunnels have been plaguing the majority of tunnel builders.Usually,the deformation of the surrounding rocks is too large,resulting in intrusion and even safety accidents such as collapse.It not only restricts the construction period,but also causes major economic losses.The main reason for these problems is insufficient understanding of deformation mechanism and evolutionary pattern of the surrounding rocks of the tunnel,especially the weak ones,which results in untargeted corresponding control measures.This paper takes the tuffs widely distributed in Zhejiang as an example,and conducts in-depth research on tuff soft rock tunnels through indoor tests,on-site monitoring and numerical simulation.Specifically,the following work are included in this research:1.Extensively study the latest research results,and carry out field geological survey work,where the focus is put on the surrounding rock structure,rock formation characteristics and hydrogeology of the tunnel.2.Considering the actual environment given to the surrounding rock,the triaxial compressive strength test of different saturated water and different confining pressures is carried out indoors to simulate the variation law of the strength of soft rock under the coupling of groundwater and ground stress in the natural stratum,after which the peak strength,residual strength,internal friction angle,cohesion and elastic modulus of this type of tuff soft rock are obtained.The laboratory test results can provide calculation parameters for numerical modeling.3.The surrounding clearance convergence and vault settlement of surrounding rocks caused by tunnel excavation is the key basis for judging the correctness of tunnel construction method and construction technology.The monitoring and measurement of excavation tunnel can help to grasp the displacement evolution pattern of surrounding rock dynamics.The data is used to guide the construction of the next stage and to predict the deformation pattern of the surrounding rock in the face.4.According to the indoor test results and the surrounding rock structure of the tunnel,the finite element numerical model is established to simulate the displacement and stress variation of the tunnel under different working conditions.The results of on-site monitoring and numerical model can be compared and analyzed.Construction advice can be provided for the next stage of tunnel excavation.