盾构隧道渣土改良理论与技术研究综述

土压平衡盾构在掘进过程中常遇到结"泥饼"、喷涌、刀具磨损等难题,需要对渣土进行合理改良,方可确保隧道顺畅掘进。常用的渣土改良剂有水、泡沫剂、分散剂、黏土矿物和絮凝剂,其中水和泡沫剂适用于各种地层,分散剂适用于黏性较大的地层,黏土矿物适用于缺乏细粒的颗粒土地层,而絮凝剂则适用于富水粗颗粒土地层,改良剂能够改变渣土的塑流性、渗透性、磨损性、黏附性、抗剪强度、压缩性等力学性质。针对盾构渣土改良难题,从渣土改良剂类型及技术参数、渣土改良评价指标及确定方法、改良黏性渣土力学行为、改良非/低黏性渣土力学行为、渣土改良下盾构掘进力学行为等5个方面,详细剖析了国内外盾构渣土改良理论和技术发展动态,总结既有研究不足之处。最后,提出了渣土改良研究方向建议：①水环境和温度对渣土改良效果影响;②黏性地层防"泥饼"新型改良剂的开发;③粗颗粒渣土改良技术;④渣土改良评价指标和体系的建立;⑤渣土改良作用下盾构掘进精细化数值模拟;⑥智能化渣土改良技术。

State-of-the-art on Theories and Technologies of Soil Conditioning for Shield Tunneling

Engineering problems such as clogging, soil or water spewing from screw conveyor, and cutter abrasions often happen during earth pressure balance (EPB) shield tunneling. As such, soil conditioning is required to ensure EPB shield tunneling. Water, foam agent, dispersant, clay minerals, and flocculant are used commonly to this end; water and foam agents are suitable for various formations, dispersant is suitable for formation with high clay content, clay minerals are suitable for granular soil formation, while flocculant is suitable for coarse-grained soil formation with rich water. Soil conditioners can affect the mechanical properties of soil such as plasticity, permeability, abrasion, adhesion, shear strength, and compressibility. The following EPB shield tunneling soil conditioning issues were reviewed:the selection of soil conditioners and determination of conditioning parameters, the evaluation index and method of soil conditioning, the mechanical behavior of conditioned soil with high clay content, the mechanical behavior of conditioned soil with no/low clay content, and the tunneling mechanics of EPB shield with soil conditioning. Theoretical and technological developments in EPB shield tunneling soil conditioning were reviewed in detail; then, the current limits of soil conditioning were summarized. Finally, it was determined that the following subjects should be researched further:① the effect of the water environment and temperature on the soil conditioning, ② the development of soil conditioner to prevent soil clogging, ③ the soil conditioning technology in coarse-grained formation, ④ the establishment of an evaluation index and system for soil conditioning, ⑤ the fine numerical simulation of EPB shield tunneling with soil conditioning, and ⑥ the intellectualization of soil conditioning.