MECHANICAL-BEHAVIOR OF A CLAY SOIL - EFFE CTS OF AGGREGATE SIZE, WATER-CONTENT AND APPLIED LOAD

Soil compaction has been the subject of intense research in recent yea rs, but the mechanisms involved in the compaction process remain poorl y understood. The objective of this study was to characterize these me chanisms for a Kamouraska clay (Orthic Humic Gleysol) using beds of ag gregates (1-2 mm and 2-3.4 mm) compressed into a uniaxial compression device. Changes in structural void ratio were monitored as a function of aggregate size, applied load and soil water content. Measurements o f tensile strength and shrinkage were also made on the larger aggregat es (2-3.4 mm) to investigate the involvement of the structural units i n the soil compaction process. Aggregate size had little effect on the shape of the compression curves. Compression of the aggregate beds wa s mainly a function of applied load and water content. The compaction sensitivity threshold was about 0.20-0.22 g g-1 at compression loads o f less than 200 kPa. This threshold water content corresponds to the a ir entry point and to the upper limit of the brittle domain of the agg regates during crushing. These results suggest the existence of a thre shold water content above which the soil becomes susceptible to compac tion even at low applied stress.