Combined effect of micro silica with clay, and gypsum as mulches on shear strength and wind erosion rate of sands

Abstract

Mulching is known as one of the fastest strategies to control wind erosion and sand dunes movement. We hypothesized that mixed micro silica with clay, gypsum and clay-gypsum as mulches will increase shear strength, threshold friction velocity and decrease soil losses of drifting sands. For this purpose, mixture of micro silica rates (0, 1, 5, 10, 15 and 20%) with clay, gypsum, and clay-gypsum applied on sand surfaces. After 60 days of mulching, shear strength, the threshold friction velocity and soil losses at a wind speed of 15 m/S at the height of 20 cm for 20 min. The results of this research revealed that the addition of 10% of micro silica in combination with clay and clay-gypsum increased the shear strength up to 10.6 and 37.5% and the threshold friction velocity up to 45.2 and 48.5%, respectively and decreased soil losses up to 100% in comparison with the samples without micro silica. Adding micro silica to gypsum had no considerable effect on shear strength, threshold friction velocity and soil losses. It was concluded that no pozzolanic reaction occurred between micro silica and gypsum and it was found that improvement in mechanical property and erodibility of clay-gypsum mulch was probably due to the pozzolanic reaction between micro silica and clay. Application of 10% of micro silica in combination with clay or clay-gypsum is therefore recommended as suitable mulch.