Study On Mechanical Behavior Of Metro Tunnel Construction By Tunnelling Machine In Weak-Broken Surrounding Rock

The 6th route of Guangzhou subway project is of complex geological conditions. The surrounding rocks are weak-broken and the surface located the residents and Haiyin Electric City. There are intensive constructions on the ground, so the environmental protection requirement of the construction of the project is of high standard. Therefore, this project required to excavate by tunnelling machine. By applying the tunnelling machine excavation, the damage of rock strata is very small, the excavation surface is smooth and the construction is relatively safe. More importantly, the vibration and noise is very small, so the effect for the surrounding residents and the surface structures is tiny. However, the power of the actual use of the EPJ-120DT cantilever-type boring machine is up to 195 kW, and during the construction, the consumption of the cutter is serious and the replacement for it is frequent, which increase the cost of the project. At the same time, there exists underground water and mud on the working surface of boring machine. This seriously affected the normal work of the efficiency of the boring machine.In this thesis, it's combined with the project practice of the parking line of East Lake station on the 6th line, study from the starting point of controlling the affect of the construction on the urban environment on the ground. Meanwhile, it's also took into account that the stability of the tunnel, the construction safety and the efficiency as well as the cost of the engineering. By applying large-scale three-dimensional FDM calculation software, FLAC^3D, it simulated the construction of the parking line tunnel by tunnelling machine and blasting method respectively, by a comprehensive and comparative analysis from the impact to the environment of tunnel construction and the stability of surrounding rock, etc. it's put forward that the best excavating scheme. At the same time, a 3D numerical simulation to forecast the effects of the construction is also be carried out. This study provides beneficial case for similar tunnel construction.1. In addition to the at home and abroad research achievements on the soft rock construction and tunnelling machine technologies, this paper discussed the various unique properties of soft rock as well as the applicability of tunnelling machine. This paper also explored the cantilever boring machine tunnel construction in soft rock application.2. Through numerical simulation methods, it carried out analysis of soft rock tunnelling machine construction from 3D dynamic simulation. It analyzed characteristics of the tunnel excavation and the support process, the stress, deformation and plastic state of the lining and surrounding rock. The different method of construction of boring machine to the subway tunnel and the stability of the tunnel are discussed. Also, the construction methods were optimized.3. By the application of geotechnical software FLAC^3D dynamic analysis module, the study made a 3D dynamic simulation of the soft rock tunnel construction by drilling and basting. The surface vibration caused by blasting earthquake and the energy release process are analyzed. At the same time, by comparing the measured data at the scene and statistics calculation error, the application of the method is verified.4. Finally, by a comparative analysis of the surrounding rock deformation and dynamic response of the construction of soft rock tunnel by tunnelling machine and blasting, then the best parking line tunnel excavating scheme is put forward: the combination of tunnelling machine and blasting method. At the same time, a three-dimensional numerical simulation to forecast the effects of its construction is also be carried out.In order to understand and master the engineering characteristics of the subway tunnel in soft rock, the analysis applied the numerical simulation method for the whole process of the construction of the tunnel. The numerical analysis methods can not lonely explain and analyze the complexity phenomenon observed in the scene and then make up for the lack of scene monitor and limited observation, but also can simulate the actual construction of the adverse wording conditions and to forecast and analyze the possible situations aroused during the tunnel construction. In this case, this paper will effectively promote the construction safety of subway tunnel.