Environmentally friendly method for stabilizing sand and silty sand using biopolymer (non-destructive test method application)

• The UPV used to investigate the long-term and short-term behavior of soil stabilized with the Agar and Guar gum. • The cohesion of sandy soil stabilized with 2 % Guar gum and Agar gum increased to 107 and 148 kPa. • The SEM images showed that the biopolymer bonds created like a bridge cause the soil particles to adhere together. • The UPV test can estimate mechanical and shear strength parameters of soil stabilized with biopolymer. In order to design geotechnical structures, it is necessary to determine the long-term, short-term and microstructural behavior of stabilized soil. This research used the ultrasonic pulse velocity (UPV) to investigate the long-term and short-term behavior of silty sand (0 and 40 % silt) improved with the environmentally friendly stabilizer of Agar gum and Guar gum, using a low-cost, fast, and non-destructive method. For this purpose, short-term behavior is evaluated with unconfined compressive strength (UCS) and indirect tensile tests (ITS), long-term behavior is evaluated with direct shear tests, and mechanical and shear parameters are estimated by UPV tests. Moreover, the microstructure of the stabilized samples was evaluated by scanning electron microscopy (SEM). This study showed that soil stabilization with Agar gum increased UCS and ITS compared to soil stabilized with Guar gum. The effective internal friction angle of the stabilized sandy soil with 2 % Guar gum and Agar gum decreased by 21 % and 10 %, respectively. The effective cohesion of sandy soil stabilized with 2 % Guar gum and Agar gum increased to 107 and 148 kPa, respectively. The SEM images showed that the biopolymer bonds created like a bridge cause the soil particles to adhere together. This research showed that the UPV test can estimate short-term and long-term mechanical and shear strength parameters of sand and silty sand soil stabilized with Agar gum and Guar gum. The R 2 values of relationships based on UPV for estimating UCS, ITS, and cohesion are equal to 0.96, 0.9, and 0.83, respectively.