团粒粒径对复合改良膨胀土强度特性的影响研究

为揭示团粒尺寸效应对膨胀土改良效果的影响,文章选用铁尾矿砂和电石渣作为改良剂来处理膨胀土,研究不同团粒粒径((0,2) mm、\[2,5) mm和\[5,10) mm)改良土的无侧限抗压强度、水稳性以及应力-应变特征,并结合微观试验分析其结构变化。试验结果表明:团粒粒径越大,改良土的无侧限抗压强度和水稳性越低,刚度越小,脆性破坏特征越明显;相对于铁尾矿砂改良,复合改良效果更佳;掺入铁尾矿砂能削弱团粒尺寸效应对改良效果的负面影响,最佳掺加质量分数为30%~40%;电石渣富集在团粒表面,使得土样结构变得松散,同时内部土改性效果较差,对试样稳定性有不利影响;而掺入的铁尾矿砂能填充于团粒间的孔隙,改善土体孔隙结构,增大土样强度。试验结果可为铁尾矿砂和电石渣应用于膨胀土改良工程提供参考。

In order to reveal the influence of aggregate size effect on the improvement effect of expansive soil, iron tailings sand and calcium carbide slag were selected as amendments to treat expansive soil. The unconfined compression strength, water stability and stress-strain characteristics of the improved soil with different aggregate sizes(0,2) mm, [2,5) mm and [5,10) mm) were studied, and its structural changes were analyzed in combination with microscopic experiments. The experimental results show that the larger the aggregate size of the improved soil, the lower its unconfined compression strength and water stability, the smaller its stiffness, and the more obvious its brittle failure characteristics. Compared to the improvement by using iron tailings sand, the composite improvement effect is better. The addition of iron tailings sand can weaken the negative impact of aggregate size effect on the improvement effect, and the optimal dosage is 30%-40%. Calcium carbide slag is enriched on the surface of the aggregates, causing the soil sample structure to become loose. At the same time, the internal soil modification effect is poor, which has a negative impact on the stability of the sample. Adding iron tailings sand can fill the pores between the aggregates, improve the pore structure of the soil, and increase the strength of the soil sample. The experimental results can provide reference for the application of iron tailings sand and calcium carbide slag in expansive soil improvement engineering.