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.

This paper introduces the engineering example of the first issue of Wuhan no.4 metro line of Wuchang railway station ~ Meiyuan district station which shield tunnel crossed the Wuchang railway station.By arranging observation points in the earths surface and sleeper on the settlement in the lines, the construction process can be monitored.The subway shield tunnel construction influence on surface deformation lines can be discussed, and the corresponding protective measures can be put forward which are caused by the shield tunnel crossing railway station and possible risk factors.In this paper, the project tracked and monitored on surface subsidence line and sleeper.With the monitoring data analysis and timely adjustment of shield tunneling construction parameters, to maintain the stability of the excavation face shield and prolapsed shield tail pipe, and take measures of synchronous grouting, secondary grouting to fill voids shield tail construction and other measures in time to ensure the safety of the projects and railway traffic.Monitoring results showed that shield tunnel construction scheme is reasonable and reliable.By the analysis of the monitoring data, some of the recommendations of the similar construction can be offered.