基于导电机制的电渗法加固吹填淤泥机理研究与效果预测

Effective treatment of reclaimed sludge is one of the key problems for reclamation project. Electro-osmosis is considered a very promising method. However, the limited knowledge into the consolidation mechanism, especially the relationship among current, drainage and the soil consolidation, has long hindered the engineering application of electro-osmosis. A series of electro-osmotic experiments will be conducted with reclaimed sludge under different conditions. The variations of electro-osmotic transport and electric conductivity of the soil will be studied. The relationship between current and electro-osmotic drainage will be analyzed. The changes of pore morphologyof the soils before and after experiments will be explored, based on which electro-osmotic dewatering and pore shrinkage will be compared. Based on the experimental studies, theoretical models for the electro-osmotic transport and electric conductivity will be built and a novel theory to compute electro-osmotic dewatering will be proposed. Furthermore, the new theory will be verified by real projects. Finally, approaches for assessment of the feasibility of electro-osmosis will be established. This study aims to reveal electro-osmotic mechanism from the perspective of electrical conductivity for the first time. The ultimate object is to facilitate effectively electro-osmotic consolidation of reclaimed sludge with reasonable and simple calculation method. The study is of great value for the widespread application of electro-osmosis in real projects.

吹填淤泥的加固是制约围海造陆工程发展的关键技术难题之一，电渗法被认为是很有发展前途的方法。但目前对电渗机理的研究存在不足，尤其是从电渗本质出发对电渗水流、电流、土体固结三者关系的研究还很欠缺，直接影响了其计算理论的可靠性和工程应用。本项目在不同试验条件下采用吹填淤泥开展电渗试验，研究电渗运移量、电导率的发展规律和关键影响因素，揭示电渗水流与电流的耦合作用机理；开展电渗和堆载对比试验，研究试验前后土体孔隙结构变化，获得电渗排水与土体固结的关联机制。据此建立电渗运移量、电导率与关键影响因素的关系式，提出基于导电机制的电渗固结模型。通过工程实例对该模型进行验证和完善，提出可靠的电渗加固效果预测方法。本项目基于导电机制揭示电渗法加固机理，目的是实现吹填淤泥的有效处理，并为之提供可靠的设计计算方法，预期结果对于推动电渗法工程应用具有重要的理论意义和实用价值。

吹填淤泥的加固处理是吹填造陆工程顺利开展的前期之一，电渗法适用于处理高含水量、低渗透性软土，采用电渗法处理吹填淤泥具有很大的发展前途，但电渗机理的认识不足和合理设计计算方法的欠缺是制约其工程推广应用的关键。电渗加固过程是一个多场耦合问题，从多场耦合角度对电渗机理的认识仍存在欠缺。基于此，本项目开展了系列电渗法和电渗-堆载法室内试验，研究了电渗中电场与渗流场的耦合作用和土体的导电机制，重点分析了电渗运移量和电渗电导率的发展规律和关键影响因素；研究了电渗中土体孔隙特征变化，探讨了电渗排水与土体固结变形的关联机制。研究发现：电渗运移量主要受土壤类型、含水量、含盐量等内因影响，外因（如电极布置形式、电势梯度等）对电渗运移量影响较小，且电渗运移量在电渗主要排水阶段基本维持稳定；土体电渗电导率主要受含水量、含盐量等诸多内部参数影响，受外部因素（如电势梯度，电极材料等）的影响较小；电渗处理后，土体孔隙的空间形态具有变光滑的趋势，结构复杂性减弱，而电渗作用对土体孔隙结构有序性的影响并不明显，通过孔隙结构定量分析发现电渗中土体收缩量小于排水量，说明电渗过程中土体处于非饱和状态，堆载作用可以进一步压缩土体、有效减小电渗排水与土体收缩的差值，因此实际工程中推荐电渗法与堆载预压或真空预压法等联合作用；基于大量数据分析，提出了电渗运移量和电导率的理论公式，推导得到基于导电机制的电渗排水量计算方法和土体固结变形估算方法，并将该方法与已有的基于Esrig理论的方法进行了比较，结果表明该方法对电渗排水量的预估准确性更高，可为实际工程应用提供理论和技术指导。