电化学-热学-力学耦合作用下盾构粘性渣土改良机理与饼化控制方法

Soil conditioning is a common measurement for controlling mud clogging during shield tunneling in clayey ground. Due to generation of heat by friction in the mud-cutter interface, electrochemical behavior of conditioning agent changes and strength of mud increases after heating. As a result, heating by friction and soil clogging develops more. Thus, the mud shows obvious coupling feature of electrochemical-thermal-mechanical behavior, and conditioning mechanism and clogging control method of clayey mud under electrochemical-thermal-mechanical coupling has been a key scientific question in shield tunnel engineering. Theories of electrochemistry, thermotics, soil mechanics and shield tunneling mechanics will be adopted for carrying out the following three researches via mutiple of tests: Firstly, electrochemcial response law of conditioning agent with clayey mud will be investigated. Adsorption capacity of the conditioning agent, grade size distribution of mud and Zeta potential will be measured to explain adaptability of chemical conditiong agent to ground and groundwater environments. Secondly, physical mechanical behavior of clayey mud will be studied. Effect of conditioning agent on Atterberg limits, shear strength, adhesion strength and temperature of mud will be analyzed to reveal electrochemical-thermal-mechanical coupling feature and conditioning mechanism of clayey mud. Finally, relationship between shield tunneling mechanical parameters, mud temperature, clogging state and electrochemical behavior will be researched, and then the controlling method of clayey mud clogging under the electrochemical-thermal-mechanical coupling will be proposed. The expected research findings will provide therotical references for shield clayey mud conditioning and have significant engineering application values.

渣土改良是解决粘性地层盾构“结泥饼”难题的常见措施，由于渣土-刀具界面摩擦生热，影响改良剂电化学反应，经“烧结”后渣土强度增高，加剧摩擦生热和渣土饼化，因此渣土呈现明显电化学-热学-力学耦合特性，电化学-热学-力学耦合作用下粘性渣土改良机理与饼化控制方法已是盾构隧道工程关键科学问题。结合电化学、热学、土力学和盾构掘进力学等理论，通过多种试验开展三方面研究：探究渣土改良剂电化学反应规律，获取改良剂吸附量、渣土粒径分布和Zeta电位变化情况，阐释化学改良剂的地层和地下水环境适应性特征；研究渣土物理力学行为，分析改良剂和地下水环境对渣土液塑限、抗剪强度、粘附强度和温度的影响，揭露渣土电化学-热学-力学耦合特征及改良机理；研究盾构掘进力学参数、渣土温度、饼化状态和电化学反应关联性，提出电化学-热学-力学耦合作用下粘性渣土饼化控制方法。预期研究成果可为盾构粘性渣土改良提供理论依据，具有重要工程价值。

针对黏性地层土压平衡盾构掘进过程中渣土改良难题，以细颗粒状黏土或粗-细颗粒混合土与改良剂混合物作为主要研究材料来模拟盾构渣土，采用室内试验、理论分析、数值模拟和现场验证等手段，深入开展盾构渣土粘附特性及改良机理研究，获得以下主要创新成果：（1）揭示不同类型改良剂对黏土液塑限的影响规律，并通过测定分散剂作用下黏土颗粒的Zeta 电位变化，结合DLVO理论，厘清了分散剂对黏土的改良机理，为渣土改良剂选型提供了科学依据；（2）自主研发了分别适用于细颗粒和粗-细颗粒混合土的旋转剪切仪，为流动性黏性渣土对金属材料的粘附特性研究提供了试验手段；（3）揭示了不同因素影响下黏土不排水粘附强度和抗剪强度变化规律以及黏土改良机理，构建了粘附强度和抗剪强度计算模型，结合黏土‐金属界面剪切破坏模式，提出了黏土粘稠指数控制范围，为黏土地层盾构渣土结“泥饼”预防提供理论依据；（4）揭示了粗-细颗粒混合土-金属界面粘聚力的变化特征，发现盾构渣土易结“泥饼”的临界粒径为0.15mm，进一步地，提出了盾构易结“泥饼”的细、粗颗粒临界表面积比为25:1，当细、粗颗粒表面积比大于25:1，盾构存在结“泥饼”风险，为粗-细颗粒混合土地层盾构渣土改良方案制定提供理论依据；（5）形成了盾构掘进黏性渣土改良技术，结合实际工程验证所提出渣土改良技术的可行性。研究成果可为盾构粘性渣土改良提供理论依据，具有重要工程应用价值。