Study On Ground Subsidence Due To The Tunnel Excavation In Hu-Ming Section Of Wuhan Subway

The excavation of city subway tunnel will lead to ground subsidence. Excessive ground subsidence will not only threaten the safety of the subway project itself, but also create a serious hazard to its surrounding buildings. One subway line is made up of two parallel tunnels. One tunnel is usually lagged behind the other when excavated in a cross-section. So the surface subsidence caused by the excavation of two tunnels will affect each other. With the fast development of infrastructure in China, the increasing numbers of subway construction are being carried out in cities. In-depth research, and the reasonable control of the underground tunnel induced ground subsidence is of great practical significance.In this paper, an in-depth study of the excavation in Hu-Ming Section has been carried out. The combined method of the theoretical calculation and numerical simulation is adopted to analyze the the results of ground subsidence measurement. The following work has been done:(1) The FEM software MIDAS/GTS have been used to simulate a great deal of double parallel tunnel excavation in soft rock. The rules of the shape deformation and ground subsidence caused by double parallel tunnels excavation in soft rock has been summarized, which makes a reference for the judgement of the ground subsidence due to general double parallel tunnel excavation in soft rock.(2) A detailed analysis has been done of the engineering geological conditions and the results of the construction monitoring of Hu-Ming Section. With the comprehensive consideration of engineering geological conditions, construction methods and spatial distribution, the studied region was divided into 5 sections,the individual surface settlement curve of which has been analyzed. Some of the surface subsidence is more than the warning value, and some is less.(3) According to the engineering practice of each typical section, MIDAS/GTS software to built the model of the tunnel excavation has been used to build. The surface subsidence due to tunnel excavation has been calculated, and fitted with measurement results, and the results were fitted with measurement results and the fitting is fine. Simulated and measured data fitting is good. The pretreatment has been made according to the measured data and soil properties of some fracture planes. The optimized simulation of surface subsidence is less than the warning value, which shows descriptions that the optimization of pretreatment is feasible.(4) Stochastic medium theory and the Peck formula are calculation methods used in the area of computation of ground subsidence caused by tunnel excavation. However, the calculation of the random medium theory is too complicated, and Peck formula can not reasonably consider he depth of the tunnel. Through rigorous mathematical derived to simplify the stochastic medium theory calculation, while retaining the depth of the tunnel parameters, a method has been found to calculate ground subsidence caused by double parallel tunnels excavation of any cross-section shape.(5) With the monitoring data, MATLAB software is used to back-analyze the key parameters of the formula, and calculation with the key parameters.The result is in good agreement with the measured data; the relation between the key parameters and the influence factors is summerized,and range of values of key parameters is given in the similar conditions to in this paper.In summary, basing on the project of Wuhan subway tunnel excavation, the conclusion is accurate in this paper. Therefore, it has some practical value in guiding the construction of Wuhan subway and controlling the ground subsidence.