电渗-氯化钙对硫酸钠盐渍土变形的影响

过多的水盐含量是季冻区盐渍土产生变形的根本原因，而电渗可以通过驱动盐离子加速土体的排水固结，同时也会导致阴极土体含水率过大，进而产生严重冻胀变形。本文采用自制装置进行电渗联合氯化钙的室内试验，研究不同氯化钙含量（质量分数为0、5%、10%、15%的氯化钙溶液）对硫酸钠盐渍土变形的影响，结果表明：电渗联合氯化钙可以增大硫酸钠盐渍土的电导率，进而加速土中水的排出，相较于仅电渗处理，土体最终电渗排水量增加35%以上；硫酸钠盐渍土中过量的Na+和SO42-在电场力的驱动下分别向阴阳两极迁移，大部分随电渗水流排出，从而降低土体中含盐量，减小低温下土体冻胀盐胀变形；在电场力作用下，Ca2+迁移到阴极并与水解产生的OH-结合形成Ca(OH)2胶结物，大大增强土颗粒间的粘结力，而多余的Ca2+与可溶性硅酸盐发生反应形成水合硅酸钙（C-S-H），并沉积在土颗粒表面，增加土颗粒间的摩擦力，有效降低阴极土体的冻胀变形；经电渗-氯化钙处理后的硫酸钠盐渍土，微观结构更加密实，抵抗冻胀盐胀变形能力显著增强，其中以质量分数10%的氯化钙溶液的加固效果为最佳，相较于仅作电渗处理土体，最终排水量提高了近70%，阴极土体...

Influence of Electroosmosis-Calcium Chloride Treatment on the Deformation of Sodium Sulfate Saline Soil

The essential cause of the deformation of saline soil in seasonal frozen region is the excess water and salt. Electroosmotic treatment can accelerate the dewatering of soil by driving the salt ions, the excessive water content of anodic soil is also induced subsequently, which will cause seriously freezing deformation. In this work, a set of comparison laboratory tests were performed in customized apparatus to investigate the influence of electroosmosis and calcium sodium application (0, 5%, 10%, 15%) on the deformation of sodium sulfate saline soil. The testing results indicate that electroosmosis incorporated with calcium chloride can dramatically improve the soil’s conductivity and drainage rate. Compared with sole electroosmotic treatment, the accumulative drainage of soil treated with electroosmosis-calcium chloride increases by more than 35%. Moreover, the surplus Na⁺ and SO₄^2- ions migrate to cathode and anode respectively, and exit with water flow, resulting in the significant decrease of frost heave and salt expansion. The free Ca²⁺ ions involved in anodic electrolyte migrate to cathode under the external electric field and react with OH^- ions. The obtained Ca(OH)₂ serves as cementing agents and improves the integrity of soil matrix. Also, the residual Ca²⁺ ions deported to cathodic area react with some soluble silicate, forming the calcium silicate hydrate (C-S-H) which coate on soil particle surface and increases the internal friction angel of soil. After electroosmosis-calcium chloride treatment, the microstructure and resistance to deformation of sodium sulfate saline soil were obviously improved. And the mass concentration of 10% calcium chloride solution achieves the best reinforcement. By comparison with sole electroosmosis treatment, the drainage volume increases by 70%, and the shear strength of cathodic soil increases 27.1 kPa, the freezing deformation decreases by 65.1%. While, once the mass concentration of calcium chloride exceeds 10%, the soil shear strength and drainage decrease because of the blockage of electroosmotic channel and corrosion of electrodes, resulting in the increment of soil deformation.