Development of a theory-monitoring integrated structure joints assessment method of prefabricated underground stations

FOJI technology framework diagram. [Display omitted] Prefabricated assembly structures have been extensively applied for the construction of low carbon and cost effective underground subway stations in China. Engineers faced significant challenges in dealing with the assessment of mechanical performance of structures joints within prefabricated underground station (PUS) structures during construction process. Manual assembly of large-scale prefabricated structures may lead to significant disturbance of structures joints, resulting in structures joints failure in construction process or even water leakage in maintenance of underground stations. To address these issues, this study proposed an integrated theory-monitoring method for joint performance assessment. The initial step involved the establishment of a fiber optical sensors (FOS) monitoring system for PUS joints. A joint performance assessment module was then developed utilizing the Joint Interfaces Contact Model (JICM) and was subsequently integrated into monitoring system, forming a joint performance assessment method, namely FOS-JICM (FOJI). A case study was finally conducted on a Shenzhen pipe jacking PUS to evaluate the effectiveness of FOJI. Main research findings of this study include (a) FOS monitoring system demonstrated excellent adaptability, accuracy, and real-time performance in practical applications; (b) FOS monitoring system effectively captured joint deformation and stress evolution throughout the entire construction process, providing insights into the impact of complex geological conditions and box culverts on joint behavior; (c) FOJI, with its integration of the JICM module, enabled safety assessment of joint performance during pipe jacking process; (d) FOJI successfully identified joint damage, offering valuable guidance for engineering restoration and protective measures. It facilitated prompt updates and adjustments based on the actual construction conditions, establishing a cycle mechanism for safety protection. These achievements not only establish a theoretical foundation for ensuring the construction safety of PUS joints but also present substantial practical application value.