Study On Surface Subsidence Caused By Subway Tunnel Excavation And Environmental Vibration Caused By Subway Train Operation

As more and more cities begin to build subway, there is growing concern about surface subsidence caused by subway tunnel excavation and environmental vibration caused by subway train operation. This paper uses the finite element software ANSYS to analyze the factors influencing on the surface settlement in Sha-Shi section construction of Shenzhen Metro Line 2. These factors are, respectively, the excavation radii of different sections, different excavation footages, different tunnel depthes, and excavation methods with or without the advance support. The obtained results show that:the larger the excavation radius, the longer the excavation footage cycle and the greater the surface settlement; the urface subsidence is inversely proportional to tunnel depth, namely the surface subsidence is smaller if the tunnel depth is deeper. The Arc Shape Step Method for tunnel excavation is the best way to control the subsidence, while, successively for The Up and Down Step Method and for The Full Face Excavation Method. The onstruction method with the advance support is also a better way to control the surface subsidence. The conclusions above are available for optimization of the subway tunnel excavation. The typical sections of gradesâ…£,â…¤andâ…¥of in Sha-Shi section are selected in the analysis. By comparing the ground surface settlement obtained by numerical calculation with the field measurement, it can be seen that their overall trend are very close, which indicate that the numerical results are credible. But the numerical values are smaller than the measured values, so some safety factors should be used to multiply the critical numerical value to guide the tunnel construction for safety. Tunnel depth, subway train speed, loading frequency, tunnel lining elastic modulus and other factors have great impact on the ground vibration. The deeper the depth is, the weaker the ground vibration is; the faster the speed is, the stronger the ground vibration will be. The calculation shows that the low frequency loading effect on the ground-bourn vibration is more durable and the high-frequency vibration attenuates faster. Under the premise of satisfied structural safety, reducing the elastic modulus of the concrete lining decreases the ground vibration caused by subway train operation.