Abstract
During the construction of deep foundation pits adjacent to existing subway structures, the complexity of engineering geological and boundary conditions renders theoretical analysis inadequate for accurately calculating deformation and internal force variations in adjacent subway structures, making the assurance of subway structural safety a critical consideration. The Guangzhou Design Capital Phase II Jiangxia Reserved Land Project features an adjacent subway structure that is an open-cut section with a double-box rectangular frame structure, with the affected section buried at a depth of approximately 5.3–8.0 m. Based on the design and construction documentation of this project and the adjacent subway structure, as well as their relative spatial relationship, this study establishes a three-dimensional finite element model to simulate construction sequences including retaining structure installation, pit excavation, support system construction, basement structure construction, support removal, and pit backfilling, thereby calculating deformation and internal force changes in the adjacent shallow-buried subway tunnel under various working conditions. Considering the effects of foundation pit dewatering and adverse geological conditions, a two-dimensional plane strain model is developed to analyze potential hazards to subway structural safety posed by water level decline and karst cave treatment. Drawing upon numerical simulation results and field measurement data from similar projects, this paper examines the influences of various factors and construction procedures on subway structural safety, explores measures to mitigate deformation of subway structures induced by foundation pit construction, and proposes specific recommendations for design, monitoring, and construction tailored to this project, thereby providing valuable references for risk control in this project and similar undertakings.
Full Text
Preamble
Analysis of the Influence of Foundation Pit Engineering on the Safety of Adjacent Shallow-Buried Metro Structures
Yuan Huanhuan, Hu Jiwei
Guangzhou Metro Engineering Consulting Co., Ltd., Guangzhou 510000
Abstract
During deep foundation pit construction adjacent to existing metro structures, the complexity of engineering geological and boundary conditions makes theoretical analysis inadequate for accurately calculating deformation and internal force variations in the neighboring metro structures. Consequently, ensuring the safety of these structures becomes a critical concern that must be addressed.
This study examines the Guangzhou Design Capital Phase II Jiangxia Reserved Land Project, where the adjacent metro structure is an open-cut section featuring a double-box rectangular frame configuration. The affected section has a burial depth of approximately 5.3–8.0 m.
Based on the design and construction documentation of both the project and the adjacent metro structure, along with their relative spatial relationship, a three-dimensional finite element model was developed to simulate the complete construction sequence. This includes retaining structure installation, pit excavation, support system construction, basement structure construction, support removal, and backfilling operations. The model calculates deformation and internal force changes in the adjacent shallow-buried metro tunnel under various working conditions.
Additionally, considering the effects of foundation pit dewatering and adverse geological conditions, a two-dimensional plane strain model was established to analyze potential hazards to metro structure safety arising from water level decline and karst cave treatment.
Drawing upon numerical simulation results and field measurement data from similar projects, this paper analyzes how different factors and construction sequences affect metro structure safety, discusses measures to mitigate deformation induced by foundation pit construction, and proposes specific recommendations for design, monitoring, and construction practices. These findings provide a valuable reference for risk control in this project and similar undertakings.
Keywords: foundation pit engineering; shallow-buried tunnel; numerical simulation analysis; metro structure deformation