Application of Grouting Method for Underground Excavation Construction of Urban Rail Transit Connecting Passage in Water-rich Sandy Cobble Stratum

Abstract

Objective Connecting Passage 1 in the interval of Jiujiang North Station and Longqiao Road Station of Chengdu Metro Line 19 Phase II is located in water-rich sandy cobble stratum. Limited by the location of the surrounding buildings (structures), it is not suitable to adopt conventional method for the construction. Therefore, the non-precipitation method is required to provide a water-free condition for the underground excavation construction of this connecting passage. Method According to the engineering characteristics of Connecting Passage 1, and based on a comparative analysis of conventional schemes such as freezing method and pipe-jacking method, the grouting method is adopted to provide a water-free condition for the underground excavation of this connecting passage. According to the characteristics of water-rich sandy cobble stratum and limited by the layout of the surrounding buildings (structures), it is decided to adopt the horizontal grouting method for Line 19 main line tunnel construction. The construction scheme of Connecting Passage 1 grouting method is elaborated in detail. In view of the difficulties such as water gushing and sand gushing in the sandy cobble stratum, hole forming difficulty, slurry leakage and spillover under dynamic water conditions, corresponding countermeasures are proposed. The advantages of the horizontal grouting method are summarized from the aspects of reliability, cost, deformation control, operation and maintenance. Result & Conclusion After completing the construction of Connecting Passage 1, water output per meter of the inspection hole is not more than 0.13 L/min after testing, achieving the expected water-stop requirement and meeting the water-free condition for the underground excavation of this passage. The excavation process shows that there is basically no water seepage on the excavation surface, and Connecting Passage 1 is safely connected.

Keywords

• urban rail transit
• connecting passage
• underground excavation construction
• grouting method
• water-rich sandy cobble stratum