Long-term monitoring and safety evaluation of a metro station during deep excavation

Abstract

The subway systems play a vital role in alleviating the urban traffic congestion problem. Recently, lots of underground railway transportation networks have been opened to operation or are being constructed in major cities of China. Due to the complexity and uncertainty inherent in excavation activities, metro station excavations brings a challenge to civil engineering communities and poses threat to the public safety in metropolitan regions. The stability of deep excavation and adjacent buildings has gained highlighted concerns during metro station construction. A viable and practical way to ensure the construction safety is by executing real-time monitoring strategy with the aid of advanced sensing and signal processing technologies. In this paper, the design and implementation of a long-term monitoring and safety evaluation system for the deep excavation of a metro station has been addressed. A software platform has been developed for analyzing and processing monitoring data based on the concept of dynamic construction inverse analysis, which includes the database system, the dynamic construction feedback system, and the deformation forecasting system. Field monitoring results in various categories during deep excavation are presented. After examining the field measurement results, the following conclusions are drawn: (i) the deformation of the diaphragm wall and ground surface settlements increased with the excavation depth; (ii) the location of the maximum horizontal displacement moved downward to the excavation face during excavation; (iii) the axial forces of struts transferred from the first row to the others during excavation; and (iv) the monitoring results indicate that the braced excavation remained overall stable at the construction stage.