A novel study on hydro-mechanical characteristics of biopolymer-stabilized dune sand

Abstract

Dune sands have low shear strength due to weak particle structures and lack of bondings. Environmental challenges, sandstorms for instance, can be occurred by the wind. Therefore, it is necessary to stabilize dune sands using environmentally friendly materials. Biopolymers are one of the suitable options due to their environmental compatibility. In this study, Salep biopolymer has been used to stabilize the dune sandy soil of Kerman desert. Different factors, including biopolymer content (BC: 3%, 5%, 10%), curing period (CP: 3, 7, 14 days), curing temperature (CT: 25, 50, 70 °C), and sample condition (SC: dry, wet, optimum) were selected to evaluate the stabilization process. L9 orthogonal array and uniaxial strength were chosen as the experimental design and main response in Taguchi methodology, respectively. The results show the highest dry unit weight is obtained with 5% replacement by weight of Salep biopolymer. Signal to Noise (S/N) values show CT and SC factors significantly affect response. Also, the optimal values of the main factors are BC: 5%, CP: 7 days, CT: 50 °C, and SC: wet condition. Next, uniaxial strength, permeability and CBR tests were conducted on the optimal samples. The results show the uniaxial strength of the optimal stabilized sample with distilled water and buffer solution is equal to 11.4 and 12.4 MPa, respectively. The permeability coefficient of stabilized samples in optimum conditions significantly reduced compared to untreated soil. Also, the unsaturated CBR strength in the optimal stabilized samples with distilled water and buffer solution increased by 12 and 13 times, respectively. The saturated CBR strength has risen about three times compared to untreated dune sand. Finally, the microstructural analysis revealed that increasing the contact surface of particles and filling the holes with Salep biopolymer effectively improved the hydro-mechanical properties of biopolymer-treated dune sand.