Improving the Shear Strength of Soils by Adding Agricultural By-Products

Improving substandard soils with stabilizing agents has proven to be more practical and economical in many cases than acquiring good quality soil. Although a number of options for the chemical stabilization of soils have been successfully demonstrated in engineering projects, the chemicals utilized are not environmentally friendly and can create secondary issues such as corrosion of materials and leaching of chemicals into the subsoil and groundwater. Developing new stabilizing agents that improve the mechanical behavior of problematic soils but have only a minimal environmental impact has long been a goal for researchers. The primary objective of this study was therefore to identify the stabilizing effect of adding agricultural by-products, in this case pea bran, to coarse and fine-grained soils (SP and CL) by comparing shear strength parameters for mixing ratios and curing periods. The results reveal that the maximum dry unit weights of the compacted SP and CL samples were reduced by 15–25% by adding 10–20 wt% of bran. The shear strength of the fine grained samples increased by up to 140% in cohesion, although the increase in friction angle was not significant. The unit weights of the mixtures with sand were reduced but their shear strength did not decrease significantly. However, biodegradation was identified as a potential drawback of using the agricultural byproduct as a soil stabilizer as the shear strength decreased after 14 days of curing and further research is strongly recommended before practical applications can be developed.