COMPRESSIBILITY AND COLLAPSE CHARACTERISTICS OF ARID SALINE SABKHA SOILS

Arid saline soils are well-distributed over the globe, with a variety of nomenclature. Along the seaboard of the Arabian Gulf, these soils e xist widely and are known as ''sabkhas''. Despite the cemented and sal ine characteristics of the sabkha matrix, a recent investigation indic ated that flooding the saline sabkha with distilled water in the conve ntional oedometer apparatus was incapable of producing a sudden reduct ion in volume and/or a significant collapse. This study proposes a mod ification to the conventional oedometer to allow water to percolate th rough the consolidating specimens under a constant head. Tests were, t herefore, conducted on undisturbed sabkha specimens to assess their co mpressibility and collapse potential whereby percolation of water was commenced under two pressures to evaluate the role of sustained pressu re on the collapse mechanisms. Despite the low compressibility of sabk has, results of these tests indicated that these arid, saline soils po ssess a high collapse potential attributable primarily to dissolution of sodium chlorides, leaching of calcium ions and soil grain adjustmen t. The collapse potential increases with an increase in the acting pre ssure at which percolation of water takes place. In contrast to other typical soils, the collapse of arid, saline soils is not instantaneous but requires sufficient volume of water to percolate in order to enha nce the dissolution of the cementing agents.