不同固结压力下强结构性黏土孔隙分布试验研究

为探讨结构性土变形的微观机制,以湛江地区结构性黏土为研究对象,对原状土和压缩试验后土样进行压汞试验,分析不同固结压力下土的孔隙分布、孔径大小以及孔隙结构特征参数的变化规律,辅以SEM图像进行孔隙形态的定性分析,并从分形理论角度对此解释与验证。结果表明,湛江黏土各孔隙组对外力的敏感度与孔隙体积含量正相关。由于压汞过程存在瓶颈效应以及边-面-角的空间接触形式,其结果可能会夸大真实小孔隙的分布密度而低估大孔隙的分布密度。结构性对压缩过程中孔隙分布影响较大,当固结压力增大至结构屈服压力后,孔径为0.01⁰.50μm的孔隙组变化明显,孔隙的连通性变差,孔径分布向小孔径范围移动,孤立式孔隙增多,大、中孔隙的界限变得不明显。湛江黏土孔隙具有多重分形特征,据此确定微裂隙、粒间孔隙和孤立孔隙孔径的分界点为0.01μm与0.50μm,同时给出了湛江黏土的孔径界定标准。

Experiment study of pore distribution of strong structural clay under different consolidation pressures

Mercury injection test on Zhanjiang natural soft clay and compressed soil is conducted to obtain the microscopic deformation mechanism of structured soft clay. Evolutions of pore distribution, size, and structural characteristic parameters under different consolidation pressures are analyzed; the pore morphology is further quantitatively analyzed by SEM image, which is explained and testified by fractal theory. The results show that, a positive correlation is shown between the sensitivity of each pore size to external forces and pore volume content. The distribution density of the fine pores might be exaggerated while the one of macro pores might be underestimated in mercury injection test for the bottleneck effect. Pore distribution is affected by structure. When consolidation pressure increases to yield pressure, pores of 0.01-0.50 μm are changing obviously, pore connectivity becomes worse, pore size decreases, isolated pores increase, and limits between pore sizes become unobvious. Zhanjiang soft clay has multi-fractal characteristics, the limits for determining micro-pores, interparticle pores and isolated pores are 0.01 μm and 0.50 μm. Pore size division standard is given.