Behavior of Gypseous Soil Treated by Arabic Gum Biopolymer Under Cycles of Wetting and Drying

Gypseous soil is classified as problematic soil since the main source that makes it problematic soil is the dissolving of gypsum in water. Treatment by biopolymers offers an environmentally friendly and sustainable way of soil enhancement that has recently been adopted by geotechnical engineers. However, it is vulnerable to periodical environmental impacts, particularly changes in moisture content. The main objective of this study is to find out the effect of wetting and drying cycles on the shear strength behavior of gypseous soil treated by Arabic gum biopolymer. Gypseous soil specimens of 40% gypsum content treated with 2% biopolymer Arabic gum were prepared for this investigation. The soil specimen was exposed to several cycles of wetting and drying (1, 5, 10, and 15 cycles). For each number of cycles, the shear strength parameters were evaluated for soil specimens. The results showed that the angle of internal friction (ɸ) increased until the fifth cycle, from 40o to 44o, and then approximately returned to its original value at 15 cycles. Similarly, cohesion increased by 67% at the 5th cycle and decreased to 58% at the 15th, respectively. Whereas the value of unconfined compressive strength (qu) decreased with the cycles increasing, reaching 54% after the 5th cycle and 68% at cycle 15th. It can be concluded to some extent that Arabic gum reduces changes and deformations in treated soil samples for a limited number of wetting and drying cycles and preserves its shear strength.