考虑饱和度变化的电渗固结模型与吹填软土快速固结试验研究

Electroosmosis is less dependent on soil hydraulic conductivity. Past research investigations have shown that the electroosmosis is mostly in favour of fast consolidation of some problematic soils of high moisture content and low permeability. In practices of consolidating recently deposited thick hydraulic fills, soils properties including compressibility, permeability, resistivity and degree of saturation change in response to the consolidation processes. The changes are usually noticeable and inappropriate to neglect and the small strain assumptions less likely stand. In the meantime, existing theories and calculations on the electroosmosis hold only if the soil mass is fully saturated, which, however, is not real. From these ends, the project will be exploring the nature of unsaturated conditions on electroosmosis processes. This will be undertaken under the framework of large strain deformation which reflects the changes of soil properties and therefore improves prediction accuracy. From there, this project will be investigating a new fast consolidation technique – coupled electrode arrays. The new technique aims to accelerate consolidation process and improve its efficiency. A 2-dimensional model will be established to assess the efficiency of the new technique. This model will be verified against experimental tests conducted on hydraulic fills recovered from Tianjin coastal areas. Expected research outputs include energy consumption, consolidation efficiency and guidance for new technique.

电渗固结受土体渗透性影响小，大量研究表明该法适合高含水率、低渗透性等不良特性的软土地基快速排水固结。当软土含水率较高,尤其是深厚新近吹填土层，关键土性参数，如压缩性、渗透性、电阻率、饱和度等，随着固结进程发生较大变化，该变化往往超过现有电渗固结理论和计算所假定的小变形范围。同时，现有理论和计算一般假设电渗为饱和固结过程，且部分土性参数为常数，与实际情况有差距。据此，本项目拟分析电渗固结过程中土体的非饱和特性，并基于大变形理论建立考虑饱和度变化的电渗固结模型。在此基础上，研究立体电极排布电渗技术，以及该新型技术对滨海吹填土的快速固结，建立该技术作用下吹填土地基二维电渗固结模型。结合天津滨海地区典型吹填土物理属性，进行模型计算，考虑能耗、固结度指标，开展地基固结优化分析，提出吹填土快速结壳及快速固结工法。成果有利于吹填土地基加快排水、缩短工时和降低能耗。

当软土含水率较高,尤其是深厚新近吹填土层，关键土性参数随电渗固结进程发生较大变化，该变化往往超过现有电渗固结理论和计算所假定的小变形范围。本项目基于非饱和土固结理论和大变形分段线性差分法，分别建立了非饱和土一维大变形固结模型UCS1、考虑饱和度变化的电渗固结模型UEC1和非饱和电渗-堆载耦合固结模型UEC2，所建立的模型可以考虑固结过程中土性参数的非线性变化，揭示了电渗固结过程中土体由饱和状态向非饱和状态转化机理。分析表明：电渗固结过程中阳极附近土体首先出现较小的负孔隙气压，并向阴极区域扩展，土体逐渐由饱和状态向非饱和状态转化；残余饱和度对电渗固结沉降量影响显著，假定土体始终饱和，电渗固结沉降偏大。. 利用电渗固结过程中阳极固结快的特点，发明了一种新近吹填土快速结壳电渗电极，该电极可用于新近吹填土快速结壳以及浅层新近吹填土快速固结。建立了三维（轴对称）电渗-堆载-真空预压联合作用固结模型，可用于分析电渗、真空预压、堆载预压三者任意组合形式的大变形非线性固结分析，开展了关键参数分析，揭示了固结度、饱和度等对电渗能耗的影响规律，研究发现当固结超过80%时，电渗能耗快速升高，控制合理固结度范围对降低电渗能耗具有重要意义。