Deformation monitoring and remote analysis of ultra-deep underground space excavation

Abstract

The development and utilization of urban underground space is producing many deep foundation pits. On-site monitoring is a key issue to ensure the safety of the foundation excavation, especially the monitoring of the lateral displacement of the structure. The ultra-deep circular foundation excavation project (58.65 m deep, the deepest foundation pit in Shanghai) in the test section of the Suzhou River deep tunnel is one of the most challenging engineering around the world. The distributed optical fiber monitoring technology of Brillouin optical frequency domain analysis (BOFDA) was employed to monitor the lateral displacement of the deep foundation. The monitoring process lasted for 14 months, and a total of 19 times of monitoring was carried out following the progress of the excavation of the foundation pit. This paper introduces the process, methods and precautions of optical fiber monitoring from early installation, equipment debugging to data acquisition, data processing and data analysis. By comparing the fiber monitoring data with the manual monitoring data, the deformation of the deep foundation excavation is analysed. The analysis results not only obtain the deformation law of ultra-deep foundation excavation, but also prove the advantages of optical fiber monitoring in deep foundation excavation. Finally, with the support of the Smart Infrastructure Service System (iS3), the research combines optical fiber monitoring with an information platform. Under the framework of the iS3 platform, an integrated data processing and analysis module for fiber monitoring is developed, and the feasibility of remote real-time collection and analysis of monitoring data is discussed. With the support of the information platform, the monitoring data can be transmitted back to the computer terminal to realize remote monitoring.