Improving Collapsibility and Compressibility of Gypseous Sandy Soil Using Bentonite and Kaolinite


The sandy soil which covers the surface layer for the investigated area consists ofhigh gypsum content (50%). The soil was found to be a “collapsible” soil. Thusbentonite and kaolinite have been used as an improving agents for such soil. Theessential idea of this study represents an investigation of the possibility of usingthese materials as additives with different percents (5%, 10%, 15%, and 20%) toenhance these soils. A testing program was conducted on 9 models of untreated andtreated gypseous soil specimens to study the behavior of such mixes as well as theireffects on physical properties, collapsibility and compressibility characteristics. Itwas concluded that a significant reduction in collapsibility reaching 80 to 82 % forthe 10 percent mixed kaolinite and bentonite respectively. Lowest compressionindex (Cc) and recompression index (Cr) have been obtained using the samepercentages of mixed additives. Generally, best improving results have beenobtained using bentonite additive (specially the ratio 10%) for its finer grains thanthose of kaolinite.