Study On Conceptual Design And Key Technology Of Combined TBM

Tunnel excavation is a task that is often faced in engineering construction.With the rapid development of infrastructure construction and resource exploitation in China,it is necessary to excavate many deeply buried long tunnels.For long tunnel projects,it is more efficient and convenient to adopt Tunnel Boring Machine(TBM)to construction.However,TBM mechanical system is huge and has poor adaptability to geological conditions.When it runs into geological conditions such as faults,fracture zones and karst caves,as well as working conditions such as strong rock burst and large deformation of soft rock,TBM is often gets stuck,buried or even scrapped.In this paper,by sorting out the research status of TBM construction,the difficulties in the construction of long tunnel TBM under complex geological conditions are summarized.In order to improve the tunneling efficiency of TBM and its adaptability to complex geology,the concept design and construction technology of Combined TBM is proposed,and its advantages over traditional TBM construction are verified by numerical simulation.Specific research contents include:(1)Based on the design principle of advanced stress release technique,Combined TBM concept design is put forward,the inflexible TBM with a large diameter is divided into two parts,including Advanced TBM and Expand TBM with the same driving direction.Advanced TBM and Expand TBM cooperate with each other and excavate independently.The Advanced TBM can be equipped with certain advanced detection to achieve high-precision advanced detection.(2)Based on the existing TBM construction technology,this paper studies the Combined TBM construction technology.It mainly includes the excavation methods and the advanced detection methods of the Combined TBM under complicated geological conditions.The prevention and control measures during the passage of large deformation of soft rock and rock burst risk section are given.If the machine gets stuck when the Advanced TBM working,the method of realizing manual and autonomous extricate is given.(3)The effect of combined TBM to excavate hard rock tunnel is studied by numerical simulation.The excavation test of the pilot tunnel with diameter of 4m,5m,6m,7m,8m,9m,10 m and the main tunnel with diameter of 13 m was carried out respectively under three groups of ground stress conditions.The experiment of direct excavation was set as the control group.By analyzing the distribution rules of energy release rate per unit area around each excavation and LERR of local energy release rate,the combined TBM excavation method is verified to reduce the energy release level,and it is safer to excavate hard rock tunnel than direct excavation.The excavation scheme with 8m as the leading diameter of the pilot tunnel is found out,which is the best scheme under the ground stress level of this test.(4)The effect of Combined TBM to excavate tunnel in soft rock is studied by numerical simulation.Combined TBM excavation test under different leading tunnel diameters was carried out,and the direct excavation main tunnel test was set as the control group.Monitor surrounding rock deformation during the excavation.The total displacement of the monitoring points in different excavation stages,the deformation characteristics in the direction of surrounding rock depth after excavation and the variation characteristics of the displacement of the monitoring points with the excavation step are analyzed.The results show that the deformation of surrounding rock of the combined TBM is smaller than that of the traditional large-diameter TBM in both the tunneling stage of main tunnel and the pilot tunnel.It is found that when 8m is used as the diameter of combined TBM pilot tunnel,it is more convenient to provide timely support and control surrounding rock deformation.