A Laboratory Study of the Collapse Behaviour of a Compacted Sabkha Soil

Sabkha soils are saline sediments, which can withstand high loads in dry conditions, but upon wetting, they exhibit significant deformation and low shear strength and hence pose great challenge to engineers. This paper investigates the collapsibility of a compacted sabkha soil of Chott El-Hodna (Algeria) using a modified oedometer, which allows water to percolate through the soil sample. The collapsibility tests were conducted on samples compacted at a variety of values of fluid contents and relative compactions using sabkha brine. The standard Proctor tests were performed using distilled water and sabkha brine, and the compaction characteristics were determined using conventional water content and fluid content methods. The results indicate that the conventional water content procedure used to plot the compaction curve overestimates the maximum dry unit weight and underestimates the optimum moisture content. The degree of collapsibility varies from moderate to severe depending on the compaction conditions (i.e. relative compaction, initial fluid content, degree of saturation). The collapse potential increases with increasing applied load and compaction fluid content and with decreasing relative compaction. Moreover, it has been demonstrated that the use of a conventional oedometer underestimates the collapse potential of saline soils.