Research on Polymer Improvement of Shield Tunneling in Medium Coarse Sand Strata with Fine Particle Content

Earth pressure balance shield tunneling is prone to spewing during excavation under conditions of large burial depth and high water pressure. Polymers are generally used as emergency modifiers to deal with spewing. Due to the high cost of polymers and the need for specialized mixing equipment on the ground to mix them into aqueous solutions, there are few cases of their application in soil conditioning. In order to explore the adaptability of water-soluble polymer in improving the formation of medium coarse sand, polymer soil conditioning was carried out for medium coarse sand with different fine-grained contents. Pressure permeability tests, critical spewing pressure tests, and flowability tests were carried out. The results show that: The permeability coefficient of improved soil is greatly affected by changes in fine particle content, while the effect of polymer addition on its permeability coefficient is relatively gentle; The flowability and critical surge pressure of the improved soil increase linearly with the increase of fine particle content; Exploring the adaptability of water-soluble polymers to the improvement of medium coarse sand residue from three aspects: permeability coefficient, critical spewing pressure, and flowability, and determining that polymers are suitable for medium coarse sand formations with a fine particle content of up to 4%; Comparing the economic benefits of the polymer with commonly used bentonite slurry, the results show that the polymer not only has a small impact on construction efficiency but also has certain cost advantages.