脱湿状态对膨胀土膨胀变形和强度特性的影响

Influence of desorption moisture state on the swelling deformation and shear strength characteristics of expansive soil

非饱和膨胀土的脱湿状态对土中水分散失速率影响较大,不同的脱湿速率又会使膨胀土呈现不同的工程性状。通过控制恒温恒湿箱的温湿度工作参数,设置不同的脱湿环境制备土样,进行土工试验,深入认识脱湿状态对膨胀土膨胀变形和抗剪强度的影响。将饱和土样脱湿到设定的不同含水率,进行有荷载膨胀率试验,结果表明:在相对湿度越大的环境下,脱湿速率越小,土体膨胀率越大;起始含水率和上部荷载越小,土体膨胀变形越大。将不同起始含水率的土样膨胀完全后放入直剪仪,进行固结直剪试验,结果表明:脱湿到不同含水率的试样,脱湿速率越小,土体越密实膨胀后的抗剪强度越大;上部荷载存在可提高土体的抗剪强度,起始含水率越小上部荷载越大土样的抗剪强度越高。研究结果可为大气作用下膨胀土边坡的防护设计提供参考,有助于对自然气候环境下膨胀土边坡的灾变进行预警,并可优化膨胀土边坡的施工方案。

The dehydration condition of unsaturated expansive soil has the greater effect on the speed of moisture dissipation, and the moisture dissipation speed has important effect on the engineering properties of expansive soil. Through the control of the temperature and humidity working parameters of the constant temperature and humidity equipments, the different environment of desorption moisture for soil tests is set up to further understand the effect of the dehumidifying condition on the expansive deformation and shear strength. The saturated soil samples are dried to the different water content to make the expansion ratio tests with vertical load. The results show that in the greater relative humidity condition, the smaller the drying rate is, the greater the expansion rate is; the smaller the initial water content and the upper load are, the greater the expansive deformation is. When the soil samples with different initial water content are fully expanded, they would be put into direct shear apparatus for consolidation shear test. The testing results show that when the soil samples are dried to different water content, the smaller the drying rate is, the more dense the soil is, and the greater the shear strength after the expansion is. The upper load can improve the soil shear strength, the smaller the initial water content and the greater the upper load is, the greater the shear strength of expansive soil samples is. The study results could be used to provide the reference for the protection design of expansive soil slopes under atmosphere, to contribute to the early warning to the disaster of the expansive soil slope under natural climate environment, and to optimize the construction scheme of expansive soil slope.