真空冷冻干燥和烘干对滑带土孔隙特征的影响试验

Pore Characteristics of Sliding Zone Soils of Huangtupo Landslide by Vacuum Freeze-Dried and Dried Methods

采用水蒸气吸附法和恒速压汞法测定了三峡库区巴东县黄土坡滑坡Ⅰ号支洞滑带土在真空冷冻干燥和烘干状态下的孔隙特征.研究表明,滑带土烘干样中墨水瓶形孔道内水分子发生凝聚、堵塞,导致其比表面积和吸附水蒸气的能力均小于滑带土冻干样.滑带土烘干样失水收缩,团粒结构更紧密,滑带土吸附势减小,在微孔区间其累积孔隙体积和最大孔隙体积均小于滑带土冻干样.在考虑水蒸气表面张力情况下,滑带土冻干样吸附和脱附的孔隙表面分形维数均大于烘干样,说明烘干样失水后在各种化学键引力作用下使孔隙表面更趋于平滑.压汞实验结果表明在微孔和中孔区间,冻干滑带土的孔隙直径和孔隙体积均大于烘干样,但孔隙直径在0.133-129.051 μm区间,烘干样的孔隙体积大于冻干样,且直径大于41.421 μm的颗粒体积比冻干样大.

The pore characteristics of sliding zone soils,treated with vacuum freeze-drying and drying methods,respectively,are studied using water adsorption and constant-rate mercury injection porosimetry in branch tunnel Ⅰ of Huangtupo landslide located in Three Gorges Reservoir.It is found that the condensation and congestion function of water vapor in the ink bottle pore of dried sample lead to smaller specific surface area and weaker water vapor adsorption ability than those of the freeze-dried sample.The shrinkage functions and weaker adsorption potential in the dried sample make the granular structure closer,which in turn leads to smaller cumulative pore volume and maximum pore volume than those of freeze-dried sample.Considering the water vapor surface tension,the pore surface fractal dimension of freeze-dried sample is greater than that of the dried samples,which indicates that the pore surface of dried samples becomes smoother with a variety of chemical bonds.The mercury intrusion porosimetry results show that the pore diameter and pore volume of freeze-dried sample are greater than those of the dried samples in the range of micropore and mesopore.But in the pore diameter range of 0.133-129.051 μm,the pore volume of freeze-dried sample is greater than that of the dried samples.The particle volume of dried sample with diameter greater than 41.421 μm is bigger than that of the freeze-dried samples.