不同初始条件下土体污染后的物理力学性质变化实验研究

土体的物理力学性质在受污染后会发生改变,同时也受到不同初始条件的影响。通过室内土工试验研究不同含水率、颗粒及矿物组成等初始条件下土体受重金属及汽油污染前后的主要物理力学性质变化规律。结果表明:随着初始含水率的增大,污染前后土体的密度均增大,当初始含水率低于最优含水率时,污染前后粉质黏土的密度变化率更大;当土体初始含水率低于最优含水率时,随着初始含水率的增加,污染粉质黏土的塑限增大而液限减小;高于最优含水率后,塑限减小而液限增大;污染前后粉质黏土的压缩系数及其相对变化率随着含水率的增大均呈增大趋势;粉质黏土的黏聚力污染前随着含水率的增大而减小、污染后则随着含水率的增大总体上呈现先减小后增大的趋势;污染前后内摩擦角均随着含水率增大而降低,低含水率时下降速率较缓,大于最优含水率后下降速率增大。土体颗粒及矿物组成对污染物污染效果也有很大的影响,总体而言,细砂相较粉质黏土在同样初始含水率及污染物作用后物理力学性质更加稳定。

Experimental study on physical and mechanical properties of contaminated soil under different initial conditions

The physical and mechanical properties will be changed after being polluted and can be substantially influenced by the initial conditions of soil. According to laboratory experiments, different initial conditions including water content, particle and mineral constitutions, were considered to analyze the changes of soil properties pre and after being contaminated by heavy metal pollutants and oil pollutant. The results were as follows: 1) as the increase of initial water content, the density of silty clay pre and after polluted all increased. When the water content is lower than optimal water content (w_op), the relative change rate of density between polluted and unpolluted soil is much higher. 2) The plastic limit increased while the liquid limit decreased with the increase of water content within the range of lower than w_op. The variations were just opposite when the initial contents are higher than w_op. 3) The compressive coefficients as well as the relative change rate of polluted and unpolluted silty soils were all increased with the increment of water content. 4) the cohesion of uncontaminated silty clay was reduced as the increment of water content, while after being polluted, it was decreased within lower water content and then increased in higher water content. The inter friction angle of all kinds of polluted or unpolluted silty clay shared the variations of reduction as the water content increased, but with a different change rate in different range. 5) the composition of particle and minerals in soils are also significantly affect the change of properties being polluted. In general, cohesionless soil with higher particles and more primary minerals are more stable than cohesive soil under the same water content and pollutants.