Chengshi guidao jiaotong yanjiu (Jul 2024)
In-situ Protection of Underground High-voltage Cable Crossing Metro Foundation Pit
Abstract
Objective With the increase in underground engineering projects, more and more projects are adopting in-situ protection technology targeting the issues caused by relocating urban underground high-voltage cables. Therefore, it is necessary to study the in-situ protection of underground high-voltage cables crossing metro foundation pit. Method Taking a metro station of Foshan Metro Line 2 Phase I project as example, the in-situ protection method of closing the enclosure structure without special techniques is analyzed when 200 kV high-voltage cables crossing the metro foundation pit. The in-situ protection measures at the intersection of pipelines and enclosure structure are introduced, along with the in-situ protection measures and calculation methods for pipelines within the foundation pit. The effectiveness of the proposed protection method is verified through construction and on-site implementation. Result & Conclusion Due to the significant impact on the safety of foundation pit, the in-situ protection at the intersection of underground cables and the enclosure structure is of utmost importance. When geological conditions are favorable, the enclosure structure construction is unnecessary at the intersection of underground cables and enclosure structure. Prior to foundation pit excavation, reinforcement and improvement measures such as jet grouting piles, MJS (metro jet system) piles, or grouting can be applied to surrounding strata. Concrete baffles can be constructed reversely at the gap of the enclosure structure during foundation pit vertical excavation process. In-situ protection of underground cables within the foundation pit can adopt suspension protection measures such as Bailey frame based on stress calculations. For foundation pit with a larger span, temporary columns can be installed in the middle of the foundation pit for span reduction.
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