EVALUATION AND CONTROL OF COLLAPSIBLE SOILS

Some compacted soils wetted under certain conditions of compaction and loading may exhibit additional settlement (collapse). To investigate the effect of the soil type, compaction water content, initial dry unit weight and applied pressure at wetting on collapse potential, 138 single-oedometer tests were conducted on eight different soils. The results indicate that well-graded soils tend to collapse more than poorly graded ones under similar conditions. Furthermore, collapse potential decreases with an increase in (1) The difference between thc sand and clay percentages; (2) compaction water content: and (3) initial dry unit weight while it increases with pressure at wetting. A multiple regression analysis was performed on the laboratory results to provide a collapse-predictive model that was substantiated by data reported by several researchers. A chart is presented to estimate (1) The collapse potential of soils under various conditions; and (2) the critical water content beyond which no collapse is expected. Additionally, a means by which collapse-susceptible soils can be classified is provided.