Analysis Of Vibration Effect And Surface Settlement Induced By TBM Excavating Subway Tunnel In Urban Area

With the rapid development of urban subway construction in China in recent years,Tunnel Boring Machine(short for TBM) has been trying to apply to subway tunnelconstruction that is located in the rock formation, such as Chongqing Subway Line6andQingdao Subway Line2. Take the complex environmental conditions in the city centerinto consideration, it is difficult to avoid an adverse impact on nearby structures. Groundvibration and ground surface settlement caused by tunneling will both affect thestructures nearby to some extent. Therefore, it is necessary to have an in-depth study onground vibration and ground surface settlement caused by tunneling. In this article,studies based on Chongqing Metro Line6project were carried out by numericalsimulation method. This study can provide a reference for the TBM construction in cities.The main contents and conclusions of this article are as follows:(1) By two-dimensional dynamic numerical analysis, the influence of TBM advancerate and the law of vibration spread were discussed. And by the spectral analysis ofvibration signals, particle vibration velocity peak and main vibration frequencyparameters were obtained. Then an evaluation of the vibration influence range and extentwas given on the basic of the Safety Specifications of Blasting Operation. It is concludedthat the vibration influence range on the ground surface is within6D (D is the tunneldiameter) away from the tunnel axis.And with the TBM advance rate decreases, the peakvibration velocity is gradually reduced.(2) Using two-dimensional finite difference software FLAC, a two-dimensionaldynamic analysis model for simulating the construction of drilling and blasting methodwas established. A comparison of vibration effect between blasting and TBM methodwas provided, including vibration intensity, vibration influence range and frequencydistribution.The results show that the vibration influence range and extent of drilling andblasting method is significantly larger than TBM method. (3) Analysis of ground surface settlement caused by TBM construction: usingthree-dimensional finite difference numerical simulation software FLAC3D, athree-dimensional numerical model of the formation and tunnel was established. And thestress release characteristics were considered in the model. According to the simulatedresult, ground deformation developments process were analyzed and discussed. Besides,the law of gorund deformation under different tunnel diameter and depth conditions wasalso analyzed. The results show that surface settlement caused by construction of smalldiameter tunnel in rock formations is small. And the tunnel diameter is a controllingfactor that affecting surface settlement, however buried depth of tunnel is not acontrolling factor.