合肥膨胀土轴向卸荷回弹变形的试验研究

为研究轴向卸荷路径下的土体回弹变形特性以及初始含水率和蒙脱石粉含量等指标的影响,以合肥膨胀土为研究对象,开展了一系列的室内一维压缩回弹试验。试验结果表明:卸荷时合肥膨胀土样的e-p曲线具有明显的先缓后陡特征;每级卸荷量越大,膨胀土产生的回弹变形量也就越大;与其他土质相比,合肥膨胀土的一维压缩回弹变形偏低;最大轴向荷载、卸荷比等指标与回弹变形指标之间具有良好的拟合函数关系;相同卸荷比条件下,试样回弹变形量随初始含水率增高而相应增大;当初始含水率较低时,试样的非饱和吸力会抑制土样的回弹变形;蒙脱石粉含量与试样的一维压缩回弹变形之间具有很好的正相关性。这表明膨胀土的胀缩性会影响到膨胀土基坑坑底土体产生的回弹变形量。

Experimental Study on Rebound Deformation of Hefei Expansive Soil under Axial Unloading

In order to study the rebound deformation characteristics of soil under axial unloading path and the effects of initial water content and montmorillonite powder content, a series of one-dimensional compressive rebound tests were carried out on Hefei expansive soil. The test results show that: The e-p curves of specimen have obvious characteristics of slow at first and then steep when unloading. The greater the amount of unloading at each stage, the greater the amount of rebound deformation produced by expansive soil. Compared with other soils, the one-dimensional compression resilience deformation of specimen is low. There is a good fitting function relationship between the maximum axial load, unloading ratio and the rebound deformation index. Under the same unloading ratio, the rebound deformation of specimen increases with the increase of initial moisture content. When the initial moisture content is low, the unsaturated suction of the expansive soil samples will restrain the rebound deformation of expansive soil. There is a good positive correlation between the content of montmorillonite powder and the one-dimensional compression rebound deformation of expansive soil. This indicates that the swelling and shrinkage of expansive soil will affect the rebound deformation of the soil at the bottom of the foundation pit.