Wetting and drying collapse behaviour of collapsible gypseous soils treated by grouting

Abstract

Gypseous soil is a collapsible soil which causes large deformations in buildings which are constructed on it; therefore, several methods were used to minimize this effect, like replacing the gypseous soil or by soil stabilization (groutingorsoilimprovement).Thisstudypresentstestresults carried out on four types of gypseous soils which have differ- ent properties and with various gypsum contents. Testing was carried out on undisturbed samples to evaluate the compress- ibility of gypseous soil under different conditions. The sam- ples were grouted with acrylate liquid. The treated samples showed that the acrylate liquid reduces the compressibility of the gypseous soil by more than 60-70 %. This is attributed to the acrylate liquid film coating the gypsum particles and so isolating them from being subjected to the effect of water. The treated gypseous samples exhibited a low collapse potential, where the acrylate liquid reduced the collapsibility of the gypseous soil by more than 50-60 %. The acrylate liquid affects the shear strength parameters of the gypseous soil by increasing the cohesion and decreasing the angle of internal friction. For the untreated soil, most compression takes place during the first cycle of loading, and then the rate of the deformation increment decreases slightly to become nearly constant at the later two cycles. For a 6-h soaking period, 15- 60 % of the settlement ratio of untreated soils occurred during the first minute, whilst for the treated soils only 2-15 % occurred during the first minute. Most compression occurs during the first cycle of loading, and then the rate of deforma- tion decreases slightly to become nearly constant at the other two cycles. Fora 6-hsoaking period, 9-44% ofthe settlement ratio of untreated soils occurred during the first minute, whilst for the treated soils only 1.5-11 % occurred during the first minute. The compression in a drying-wetting con- dition was less than that of the compression in wetting repeated test by 20 %.