ABSTRACT
An experimental study was performed in order to investigate the production and development of the plastic strains of a subgrade soil under repeated loads. A clayey soil, compacted in a Proctor mold with different compaction water content and energies, was subjected to repeated punching effort ranging from 200–600 kPa for about 40000 repetitions. Cumulative plastic strain was first plotted against the number of load repetition, and then against the water content. The results show that, under relative dry condition, the cumulative plastic strains are negligible and are independent of the water content; then, the cumulative plastic strains increase more and more rapidly; at last, as water content exceeds a certain limit, the specimen cannot support the vertical stress and some soil expelled from the Proctor mold. In order to describe the above phenomenon concerning the development of the plastic strains, softening limit (wS), expulsion limit (wE) as well as stability/transition/expulsion zones were defined and then integrated in the compaction curve, which is widely used in engineering practice. In addition, the plastic strains produced in the first cycle was compared and discussed.
