膨润土干湿循环变形实验研究

Experimental Study of Bentonite Deformation under Drying/Wetting Cycles

膨润土作为防渗材料填充在煤炭开采产生的采动裂隙区保护地下水资源的过程中,地下水位的变化使膨润土受干湿循环作用。为获得膨润土干湿循环条件下脱湿与吸湿变形规律,对不同初始含水率膨润土试样进行脱湿与吸湿变形实验。结果表明,膨润土脱湿变形呈现明显的非均匀性且出现龟裂现象。利用Matlab编程识别图像方法,得到了不同初始含水率下膨润土脱湿收缩与吸湿膨胀变形随含水率变化规律曲线,从中可以看出,膨润土脱湿收缩过程曲线斜率变大,吸湿膨胀过程曲线斜率变小;初始含水率越高,缩胀变形越明显。通过实验数据拟合出了与变形过程和初始含水率相关的双参数递增指数函数关系。膨润土脱湿后重新吸湿,干缩与湿胀曲线不重合,且初始含水率越低,干缩与湿胀曲线越接近。

Bentonite experienced drying-wetting cycles due to the change of groundwater level when it is filled in mining fracture zone to protect groundwater resources as an impermeable material. The moisture desorption and moisture absorption experiments in different initial moisture content conditions are conducted to study the bentonite deformation law during the processes. The results indicate that the bentonite deformation is extremely heterogeneous during moisture desorption and accompanied with crazing. The curves of deformation of dry shrinkage and wet swelling and moisture content with different initial moisture content are obtained by image recognition method using matlab programming. It shows that the slope of curve increases when moisture content reduces in the process of moisture desorption shrinkage and reduces when moisture content increases in the process of moisture absorption swelling. Fitting formula based on experimental data reveals a two-parameter increasing exponential relation between deformation and moisture content correlation with absorption, desorption and initial moisture content. Shrinking and swelling curves are no coincidence. The lower the initial moisture content is, the closer the shrinking and swelling curves.