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

Experimental Study on Physical and Mechanical Properties of Contaminated Soil under Different Initial Conditions

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。

The physical and mechanical properties of soil can be changed after being polluted and substantially influenced by the initial conditions.According to laboratory experiments,different initial conditions including water content,particle and mineral constitutions were considered to analyze the changes of soil properties before and after being contaminated by heavy metal pollutants and oil pollutant.Results are as follows.the density of silty clay before and after polluted both in creased as the increase of initial water content.When the water content is lower than optimal water content,the relative change rate of density between polluted and unpolluted soil is much higher.When the initial water content of soil is lower than optimal water content,the plastic limit of contaminated silty clay increases while the liquid limit decreases with the increase of the initial water content.Above optimal water content,the plastic limit decreases and the liquid limit increases.The absolute value and the relative change rate of compressive coefficients of polluted silty clays increase with the increment of initial water content.The cohesion force of silty clay is reduced with the increase of initial water content before pollution.After pollution,it decreases within lower water content and then increases in higher water content.The inter friction angle of silty clay before and after pollution decrease as the initial water content increases.The rate of decrease is slow when the water content is low and increases when it is larger than the optimal water content.The composition of particle and minerals in soils also significantly affects the change of properties after pollution.In general,fine sand with higher particles and more primary minerals are more stable than siltyclay under the same water content and pollutants.