非饱和重塑土的干燥收缩试验研究

基质吸力和净平均应力的增大均可引起土体的压缩变形。针对砂土、粉土、黏土和软土4种不同类型土体,结合试样收缩曲线和土水特征曲线分析了土体干燥过程中基质吸力和孔隙比的关系。试验结果表明:土体干燥收缩过程中随着基质吸力的增大试样不断发生收缩,当基质吸力增大到某特定值时,基质吸力的增大对试样收缩变形无明显影响,称此基质吸力为缩限吸力。屈服吸力s0和缩限吸力ss将试样收缩过程分为弹性阶段、弹塑性阶段和缩限阶段3个阶段。并且不同类型土体的缩限吸力不相同,缩限吸力值与土体的塑性指数密切相关。在干燥收缩过程中,当试样的饱和度减小到90%时试样完成了绝大部分收缩,当试验饱和度达到70%时土样的孔隙比基本保持不变。

Experimental study on drying shrinkage of unsaturated compacted soils

Compression of soils could be caused by the increase of both matric suction and net mean stress.The empirical relationship between the matric suction and the void ratio on drying path was established for four types of soils including sand,silt,clay and soft clay by utilizing the shrinkage curves and the soil-water characteristic curves determined through experimental tests.It was indicated that during the process of drying,the soil samples continuously shrunk with the increase of matric suction.That is,Once the matric suction increased to a given value when the increase of suction would display no obvious effect on the shrinkage deformation of the soil samples and it was defined as the shrinkage limit suction ss.The values of ss were dependent on the plasticity index of soil.The process of shrinkage of soil was divided by the yielding suction s0 and the shrinkage limit suction ss into three stages,i.e.,elastic stage,elasto-plastic stage and stage of shrinkage limit.Moreover,in the process of drying-shrinkage of soil samples,the shrinkage of the soil samples was almost fulfilled when the degree of the saturation of soil samples decreased to 90% and the void ratio of the soil samples almost kept unchanged while the degree saturation of soil was reduced to 70%.