Deformation monitoring of ultra-deep foundation excavation using distributed fiber optic sensors

Abstract

The development and utilization of urban underground space is producing a large number of deep foundation pits. On-site monitoring is a key issue to ensure the safety of the foundation excavation, especially the monitoring of the horizontal displacement of the structure. The rapid development of distributed fiber optic sensors technology in recent years could avoid the deficiencies of manual monitoring methods, which can quickly, real-time and continuously monitor the horizontal displacement of deep soils. At the same time, with the support of the information platform, the monitoring data can be transmitted back to the computer terminal to realize remote monitoring. This paper relies on the ultra-deep circular foundation excavation project (58.65m deep, the deepest foundation pit in Shanghai) in the test section of the Suzhou River deep tunnel, and uses the distributed optical fiber monitoring technology of Brillouin optical frequency domain analysis (BOFDA) to monitor the horizontal displacement of the deep foundation. 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. The analysis results not only obtained the deformation law of ultra-deep foundation excavation, but also proved the advantages of optical fiber monitoring in deep foundation excavation. Finally, the data has been uploaded to the digital platform for remote monitoring in the future.