非饱和原状残积土土水特征曲线研究

利用压力板仪装置开展不同竖向应力、不同干湿循环次数和不同类型原状土(残积黏性土和残积砂质黏性土)的SWCC曲线试验研究, 比较和分析未考虑体积变化和考虑体积变化的土体SWCC滞回圈面积以及进气值和出气值的变化规律。研究结果表明传统方法获取的SWCC曲线会高估土体抵御变形的能力, 试验条件变化引起土体内部结构调整是SWCC曲线发生变化的内在原因; 高应力水平条件下, 土体孔隙变化显著, 导致吸湿过程SWCC变化明显, 吸湿和脱湿路径时SWCC形状的不平等变化促使彼此间更为接近, 这种变化会减小SWCC滞后性随有效应力水平的变化。最后, 根据试验数据对3类SWCC修正公式进行拟合优度分析, 结合模型参数的简洁性, 得出修正VG模型最符合闽东南地区原状残积土的SWCC建模。研究成果可为残积土边坡的工程特性及治理提供有意义的参考。

RESEARCH ON SWCC OF UNSATURATED NATURAL RESIDUAL SOIL

The stress-dependent pressure plate extractor system is used to study the residual soil SWCC curve of different vertical stresses, drying and wetting cycles and different types of natural residual cohesive soil and residual sandy clay. Then the laws of SWCC hysteresis loop area with and without volume change and AEV and AexV of residual soils are analyzed and compared. Results show that not only the ability of soil to resist deformation can be overestimated by the traditional method of SWCC curve, but also the underlying cause of SWCC curve changing is due to soil internal structure change constantly; Meanwhile, the higher net stress levels are, the larger size pores are much more influenced by the net stress. Thus the wetting branch is much more affected. The observed unequal change in the shape of drying and wetting branches of SWCC at higher net stress values brings them close to each other, and reduces the SWCC hysteresis as the net stress level increasing. Finally, according the simplicity of model parameters and the goodness-of-fit analysis results of the 3 kinds of improved SWCC models, the improved VG model has been found to be the most suitable model for all SWCC of the natural residual soil in southeast of Fujian. The above research is useful and meaningful as reference for the engineering characteristics and governance of the residual slope.