温度与化学溶液对膨胀土中土−水作用的影响

Influence of temperature and solution on soil−water interaction in expansive soil

为了研究温度与化学溶液对膨胀土物理力学性质的影响机理,基于核磁共振技术分析了温度与化学溶液对宁明膨胀土中孔隙水动力学参数的影响,基于Arrhenius定律分析了宁明膨胀土纵向弛豫时间T_(1)随温度的变化规律。研究结果表明:膨胀土中孔隙水基本处于吸附状态,平移相关时间和表面停留时间分别为1 ns和30μs;孔隙水有效扩散系数为3.61×10^(−7) cm^(2)/s,比自由水扩散系数低2个数量级。宁明膨胀土T_(1)分布呈基本对称的单峰,具有最低吸附水含量的CaCl_(2)溶液饱和试样具有最低的有效活化能,但吸附水含量最高的饱水试样有效活化能比NaCl和KCl溶液饱和试样活化能低。这主要是因为孔隙溶液中离子在降低双电层厚度的同时也降低了离子水化层的活动度,导致有效活化能升高。所有试样活化能均大于零,表明膨胀土渗透系数随温度升高而增大。

In order to clarify the influence of temperature and chemical solution on the physical and mechanical properties of expansive soil,water dynamical parameters of confined water in Ningming expansive soil,which was saturated with different solutions,were investigated with NMR technique at different temperatures.The variation of T_(1) distribution of Ningming expansive soil with temperature was analyzed based on the Arrhenius law.The results show that the confined water is retained by surface force.The translational correlation time and surface residence time are 1 ns and 30μs,respectively.The effective diffusion coefficient of pore water is 3.61×10^(−7) cm^(2)/s,which is two orders of magnitude lower than that of bulk water.The T_(1) distribution of Ningming expansive soil presents basically as a symmetrical unimodal.The sample saturated with the CaCl_(2) solution with the lowest adsorbed water content has the lowest effective activation energy,but the effective activation energy of water saturated sample with the highest adsorbed water content is lower than that of the samples saturated with NaCl and KCl solutions.This is mainly because the ion hydration decrease the thickness of the double layer and mobility of hydration layer simultaneously,leading to the increase in the effective activation energy.The positive activation energy of the samples indicates that the permeability coefficient of expansive soil increases with the increase of temperature.