In the construction of subway tunnel, a connected aisle is often set in the middle section of the upper and lower parts of the tunnel. The connected aisle is set to increase the safety factor of the tunnel, known as the "escape route". Connected aisle construction is after the completion of the main tunnel and it would have impact on the main tunnel and the surrounding environment to a certain extent. Wastewater pumping house is often combined with connected aisle in construction, but the pumping house design is relatively conservative. Construction technology is constrained by space, so it is more likely to cause risks. Therefore, effective measures are crucial to ensure the safety of excavation. In this paper, the first support deformation risk of a connected aisle of Wuhan Metro tunnel is used as an example, which uses backfill backpressure, first support reinforcement methods and acceleration of the floor construction, providing reference of risk control techniques for similar projects.

Taking Changfeng station of Wuhan Metro Line Ⅶ as an example, this article shows that the process of ultra-deep excavation have many risks by theoretical analysis of Fault Tree, such as leaking joints, longitudinal instability, pit deformation, gushing water and sand, surface subsidence around the base hang basement uplift and so on. The article analyses the monitoring data during the excavation of Changfeng station in May including the inclinometer of underground continuous wall, soil subsidence, post settlement and so on. The analysis results show that large underground continuous wall inclinometer, upright settlement, underground continuous wall seepage etc. are the signs of large pit deformation, as well as common risks of ultra-deep excavation process. So we should erect steel braces timely, grading excavation, strengthen monitoring and provide rainfall timely to control them. By timely warning and taking appropriate security measures, the excavation pit risk of Changfeng station was controlled effectively, and the main structure of Changfeng station was completed successful. The success of early warning and control of Changfeng station excavation risks can provide recommendations for the Wuhan soft soil excavation.

The foundation pit dewatering of subway station during excavation is an important part of the work progress.However, the job location of the subway station is generally located in the region of high population flow, and the foundation pit dewatering always brings some bad influence on the surroundings.So the foundation pit dewatering should be studied and analyzed.Based on a metro station of Line No.6 of Wuhan Metro, this paper explains the change law of surrounding building settlement and deformation of retaining structures by using the practical nonitoring data during the process of foundation pit dewatering.Main conclusions are as below:1) in terms of the influence of surrounding buildings, the effect of external foundation pit dewatering is much bigger than that of internal foundation pit dewatering; 2) the effect of external foundation pit dewatering can reduce the active earth pressure of the foundation pit lateral in some degree, and then reduce deformation of retaining structures; 3) the soil property and condition of foundation pit dewatering would have a great impact on the deformation of retaining structures.

Research Purpose:With the construction and development of urban subway, the problems emerge during the metro construction when the shield tunnel traveling existing lines increased. In order to explore the influence when the shield tunnel traveling the operating line, this paper discussed different control measures based on the data recorded during the metro construction in a city and made a concrete analysis of each measure according to the deformation. Research Conclusion:To reduce the effect on the operating line when the shield tunnel traveling track group of the Beijing-Guangzhou Line, the paper made a concrete analysis of settlements of construction area. The study found that although the settlements of ground, ballast and the sleepers is higher than usual, the operation safety was ensured with the help of several control measures.