絮凝-真空预压-电渗联合处理吹填流泥的加固机理及固结理论研究

The tideland reclamation is an important measure for relieving the stress of limited land resources in coastal city of China. However, the dredged marine clay fill applied in tideland reclamation projects has been characterized by high water content, high compressibility, high viscosity and other special engineering properties. The traditional vacuum preloading often leads to poor treatment of ground and engineering disasters. This project improves flocculation behavior of the dredged marine clay fill and reduces clogging in the vacuum preloading by analyzing the microstructure and particle composition of it and flocculation test. Then, based on the large-scale model test of flocculation-vacuum preloading- electro osmosis method, the interaction mechanism of flocculation, vacuum preloading and electro osmosis is investigated. The consolidation mechanism of flocculation-vacuum preloading- electro osmosis method is revealed. In addition, this research is on the basis of large deformation consolidation theory, the theory of porous media and the theory of thermodynamics, establishing consolidation analysis model, which considers the multi-coupled field of stress, seepage, electricity and temperature. The corresponding calculation program is compiled for calculation and analysis, and the results are compared with the test results. Finally, according to the results of experimental and theoretical analysis, the optimum design method of flocculation-vacuum preloading- electro osmosis method for the treatment of the dredged marine clay fill is proposed. The conclusion from this project is of important theoretical value and has a broad future in engineering applications.

海涂围垦是缓解我国沿海城市土地资源紧张的一个重要手段。但围垦工程中的吹填流泥具有含水率高、压缩性大、粘性大等特殊工程特性，采用传统的真空预压法进行地基处理往往效果不佳，容易导致工程事故。本项目拟首先通过对吹填流泥的微观结构和粒度组成的分析，以及絮凝试验，优化吹填流泥的絮凝效果，减缓真空预压法中的淤堵效应；其次，采用絮凝-真空预压-电渗大型模型试验，研究絮凝、真空预压、电渗的相互作用机制，揭示絮凝-真空预压-电渗法处理吹填流泥的加固机理，并基于大变形固结理论、多孔介质理论和热力学理论，建立可考虑应力−渗流−电场-温度多场耦合作用的吹填流泥固结分析模型；然后，编制相应的计算程序进行计算分析，并与试验结果进行比较验证；最后，根据试验和理论分析的成果，提出絮凝-真空预压-电渗法处理吹填流泥的优化设计方法。本项目的研究成果不仅具有一定的理论价值，而且具有很好的工程应用价值。

海涂围垦是缓解我国沿海城市土地资源紧张的一个重要手段，但传统真空预压法在处理高含水量吹填流泥时效果不佳，难以深入到深层土体，无法满足工程建设对于地基强度及变形的要求。本项目先通过室内试验分析了不同的絮凝剂和不同的掺入量对吹填流泥的絮凝效果，明确最优絮凝剂种类和最佳掺入比；其次通过室内大型模型试验，研究了絮凝、真空预压、电渗的联合作用机理，探索真空度、排水板间距、电渗的启动时间、间隔时间等对地基处理效果的影响，获得基本物理参数、化学参数和电学参数的变化规律；然后假设土体内电荷传递满足欧姆定律，渗流满足达西定律，推导了电渗处理吹填流泥的固结计算模型，分析了电流场与渗流场耦合作用下吹填流泥的沉降和平均固结度变化规律；最后结合实际工程通过现场试验验证了絮凝-真空预压法处理吹填流泥地基的效果。研究结果表明：在吹填流泥中加入0.8％FeCl3或0.08％阴离子聚丙烯酰胺（APAM）可以更好地加速吹填流泥的固液分离；与普通真空预压相比，在FeCl3和APAM的作用下排水量分别增加了46.5％和56.8％，吹填流泥体积减少了60.5％和82.4％，且当复合絮凝剂的复合比为1：5时，吹填流泥的含水率可从140％降低到50％以下；与等应变假设相比，自由应变假设对平均固结度没有显着影响，但对超孔隙水压力在径向的耗散和土体表面沉降有显著影响。絮凝-真空预压-逐级加压电渗法与传统真空预压联合电渗法相比，土体出流量更多，土体表面沉降更明显；在现场试验中，与传统真空预压法相比，经絮凝-真空预压法处理的地基土体，其强度提高了1倍，体现了絮凝-真空预压法的优越性。本项目通过对絮凝、真空预压、电渗三种方法联合使用的研究，达到了显著提高地基处理效果的目的，为工程实践了提供理论基础和技术支持。