基于孔径分布的全风化泥岩持水曲线推算

采用压力板法、滤纸法和饱和盐溶液蒸气平衡法，分别对取自广西岑溪滑坡现场的全风化泥岩原状样进行了持水特性试验，得到全吸力范围内的持水曲线；用压汞试验测试经受不同吸力原状样的孔径分布，并用此分布曲线推算持水曲线。试验结果表明：全风化泥岩原状样的进气值为110 kPa，用3种方法可测得全风化泥岩的全吸力范围内的持水曲线。全风化泥岩原状样的孔隙大小分布可认为单峰结构，其孔隙的孔径主要分布在10～1 000 nm，但也有孔径在50～300 ?m范围内的小部分孔隙存在，主要因为原状样中存在少量的原生裂隙。利用3个经受过不同吸力土样的孔径分布分别推算其持水曲线，3条曲线组合与实测值比较表明，用一次压汞试验结果（孔径大小分布曲线）预测全吸力范围内的持水曲线精度较低，而选取各自吸力范围段的预测曲线组合而成全吸力范围持水曲线，与试验数据更为接近。

Determination of water retention curve of fully weathered mudstone using its pore-size distribution

Water retention of undisturbed fully weathered mudstone, from Dayezhen landslide at Cenxi city, Guangxi province, is measured using pressure plate method, filter paper method, and vapor equilibrium technique with saturated salt solution. The water retention curves in a large range of suction are obtained. Mercury intrusion porosimetry is used to measure the pore-size distribution of the intact samples under different suctions. The test results show that the air-entry value of the fully weathered intact samples is about 30 kPa and the water retention curve in the full suction range can be measured by three methods. The undisturbed natural specimens exhibit a unimodal pore-size distribution with a main range of 10-1 000 nm in diameter and a secondary pore diameter distribution of 100-300 μm due to occurrence of primary crack. By comparing the results of the mercury intrusion porosimetry tests on the mudstones experiencing three different suctions, a method for predicting the water retention curve of undisturbed specimens during drying is proposed, and the predicted results are compared with the measured values. The comparison shows that the combination of three predicted curves is closer to measured results of the mudstone in the full suction range. The predicted curve using single pore size distribution curve cannot match measured water retention curve correctly in the full suction range.