Micro-settling control technology for shield tunnels crossing old buildings

The settlement control of shield tunnels in the central cities crossing the old buildings is increasingly the focus of shield construction. Generally, the settlement control method is the secondary grouting according to the surface subsidence monitoring data, but deformations of surface and buildings have already occurred. In order to make up for the shortcomings of the traditional method, the construction control technology of "micro-settling" is put forward, which includes a real-time detection technology for grouting behind segments by using the radar and automatic monitoring and warning platform and takes measures before surface deformation. It is applied to the Wangsheren-Peijiaying interval tunnel of Jinan Rail Transit R3 line under-passing through the old buildings. The construction time of the buildings is mostly in the 70 s and 80 s of the twentieth century. Some of the walls are severely weathered, which greatly increases the difficulty to control the surface settlement and protect the buildings. Firstly, by using the three-dimensional finite element software PLAXIS 3D, the numerical simulation of the tunnel crossing the Suning Building and Agricultural Bank of China is carried out. It is considered that increasing the grouting pressure can effectively reduce the surface settlement. The simulated results are in good agreement with the monitoring data. Secondly, in order to control the surface deformation of the tunnel crossing the dormitories of Chemical Fertilizer Plant, the real-time detection technology of the post-grouting by radar is developed. The grouting quality is detected during segment fixing, and the grouting pressure and capacity are dynamically adjusted to effectively control the surface settlement. At the same time, the project uses a combination of automatic and manual monitoring devices to monitor real-time deformation of buildings and surface. The engineers can grasp the construction information through the mobile phone applications, and timely measures can be taken. Combing the real-time radar detection results and surface monitoring results, the ground settlement is controlled within 0~-5 mm, and finally the goal of “micro-settling” is achieved. The building has been well protected.