Field Deformation Study on Enclosure Structure and Environment of Subway Shaft Construction under Complex Conditions

Abstract

Shafts play an important role in subway construction. Some shafts will be retained and used as an important part of the permanent subway structure after the excavation. More knowledge about the deformation mechanism of shaft construction is needed as it has a great influence on the safety of the subway construction. Based on a shaft construction of Changchun Metro1, this paper systematically analyzes the impact of various factors on the enclosure structure and its surrounding areas by examining a large number of monitoring data obtained in real-time during the shaft construction. The results show that the inverted side-wall method is appropriate for shaft construction under complex conditions, as this method of construction would provide a good control over the deformations of the shaft enclosure structure and the surrounding layers. The real time monitoring data show that the ground settlements during shaft construction are greatly influenced by local loads and construction traffic applied on the ground surface; e.g., the ground adjacent to the shaft loaded with excavation muck piles settled significantly more than the other side that was less loaded or not loaded. In addition, rapid change of groundwater level during construction dewatering could also significantly impact the shaft structure and its surrounding environment, especially for the surrounding ground settlement. The result of this study could provide some useful information for the design and construction of similar engineering structures.