干湿循环下高庙子钙基膨润土持水和变形特性

膨润土因具有湿胀、干缩特性，其水力-力学性质易受干湿循环的影响。采用饱和盐溶液蒸汽平衡法研究了干湿循环对压实高庙子钙基膨润土持水特性的影响。对相同条件下制作的试样进行0～6次干湿循环，选取其中的原试样（0次）、循环3次和6次试样，进行蒸汽平衡法试验，测定其土-水特征曲线。同时，在0～6次干湿循环过程中，对每一次脱湿后试样表面采集图像，用数字图像处理技术提取了收缩及裂隙开展区域，分析得到收缩率与裂隙率。试验结果表明：随着干湿循环次数的增加（0→3次时），土-水特征曲线向下平移、持水性下降、孔隙比增大、平均骨架应力减小，试样烘干时收缩率和裂隙率增加明显；但随着循环次数的继续增加（3→6次时），持水性、收缩率和裂隙率趋于稳定。

Water-retention and deformation characteristics of Gaomiaozi Ca-bentonite during wetting-drying cycles

The hydro-mechanical behaviours of bentonite are prone to be affected by the wetting-drying cycle due to its swelling-shrinking deformation characteristics with the moisture changing. Vapor equilibrium method using saturated salt solution, is used to measure water-retention behaviour of compacted Gaomiaozi Calcium bentonite after wetting-drying cycles. The specimens compacted at the same initial condition, are subjected to one to six wetting-drying cycles, and then the original specimen and the specimens after three and six wetting-drying cycles are selected for measuring their water-retention curves(WRC). When every wetting-drying cycle finished, the pictures of the specimen surface are taken. The pictures are dealt by the digital image processing, and then the shrinkage and crack areas are extracted. The rates of shrinkage and crack to original specimen area are obtained. Test results show that, with increasing wetting-drying cycles (0→3), the WRC moves down, water retention capacity and average skeleton stress decrease. Void ratio, the rates of shrinkage and crack after oven dry increase obviously. But after three cycles (3→6), the changes in the above mentioned behaviour become stable with increasing wetting-drying circle.