Enhancing mechanical behaviors of collapsible soil using two biopolymers

This study aims to investigate the possibility of using biopolymer(environmental friendly material) to enhance the mechanical behaviors of collapsible soil.Two types of biopolymers were(xanthan gum and guar gum) used in this study due to their stable behaviors under severe conditions and their availability with reasonable prices.The experimental program focused on three major soil properties,i.e.compaction characterizations,collapsible potential and shear parameters.These three properties are essential in process of soil improvement.Different biopolymer concentrations were used in this study and the experimental program was performed at two curing periods(soon after mixing the soil with the biopolymer and after one week curing time).Shear parameters were measured for the treated specimens under both soaked and unsoaked conditions,while a collapsible potential test was performed under different mixing conditions(wet mix and dry mix).A numerical model was built to predict the behavior of the treated collapsible soil after and before water immersing.The results indicated that the ability of both xanthan gum and guar gum can be used as improvement materials for collapsible soil treatment.The collapsible potential has been reduced from 9%to 1%after mixing the soil with 2%biopolymer concentration in the wet case.After one week curing,the cohesion has been increased from 8.5 kPa to105 kPa by increasing the xanthan gum concentration from zero to 2%,leading to an overall improvement in soil shear strength.It also proves that the guar gum is superior to the xanthan gum.The shear strength of soil can be increased by about 30%when using the guar gum in comparison with the xanthan gum at the same conditions;however,the collapsible potential of soil material will be reduced by about 20%.