Comprehensive Construction Technology for Atmospheric Pressure Opening in Soft and Rich Water Strata

This article is based on a certain rail transit project in Guangzhou. In order to avoid the occurrence of pipe blockage, compartment blockage, and adverse effects on the stability of the tunnel face during shield tunneling operations in water rich and weak strata, a new construction technology is proposed for shield tunneling under atmospheric pressure in water rich and weak strata conditions. This technology uses geological analysis of reinforcement and opening positions and pressure control of mud water balance. It adopts a dual reinforcement of inert grouting and acrylic acid salt chemical grouting, real-time control of grouting pressure, formula, viscosity, mixing ratio, and analysis of ground settlement data. The stability and excavatability of the slurry are detected through core sampling and other methods to enhance its support performance and ensure the safety of personnel in opening the warehouse and changing knives. A new type of mixing rod is installed to fully stir and deal with the problem of slag accumulation. Research has shown that: (1) the new technology can make the palm face more stable, and the ground settlement value and rate are much better than traditional methods; (2) a new high-strength skeleton grid consolidation body has been formed to improve soil reinforcement, sand layer water blocking performance, and stability, ensuring safety and stability during the opening process; (3) the new type of mixing rod can greatly solve the problem of pipe blockage caused by floating slag, and the research results can provide effective construction guidance for shield tunneling in water rich sand layers.