土压平衡盾构在大埋深、高水压地层条件下掘进时极易发生喷涌现象,聚合物一般作为应急改良剂来处理喷涌事故。由于聚合物较为昂贵且需在地面设置专门的搅拌设备拌成水溶液,其应用于渣土改良的案例较少。为了探究水溶性高分子聚合物改良中粗砂地层的适应性,针对不同细粒含量的中粗砂进行聚合物渣土改良,开展有压渗透试验、临界喷涌压力试验、流动度试验。结果表明:改良后渣土的渗透系数受细粒含量变化的影响较大,而聚合物的掺入量对其渗透系数的影响较为平缓;改良后渣土的流动度、临界喷涌压力随细粒含量的升高而线性增大;从渗透系数、临界喷涌压力、流动度三方面探讨水溶性聚合物对中粗砂渣土改良的适应性,确定聚合物适用于细粒含量3.8%以上的中粗砂地层;将聚合物与常用的膨润土泥浆进行经济效益对比,表明该聚合物不仅对施工效率的影响小,而且在成本上有优势。
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.
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