Use of Vetiver grass and Microorganism for preventing soil erosion in laboratory

Abstract

This paper studies the direct shear strengths of vetiver grass and the microbially induced calcium carbonate precipitation (MICP) process for sandy soil erosion control. The conventional direct shear tests were conducted on four sample types, including untreated sand, sand reinforced with vetiver grass, MICP-treated sand, and MICP-treated sand reinforced with vetiver grass.  The results show that the cohesion of untreated sand was 2.7 kPa, whereas the cohesion values of sand reinforced with vetiver grass, MICP-treated sand, and MICP-treated sand reinforced with vetiver grass were 7.3, 16, and 18.9 kPa, corresponding to improvement ratios of 2.7, 5.9 and 7.0 respectively. However, strength improvements with vetiver grass and MICP had a negligible impact on the internal friction angle of the test samples.  The scanning electron microscope results show that the calcite crystals and calcium components filled the voids between sand particles. This phenomenon indicated a significant increase in the cohesion value of the MICP-treated sand samples. Therefore, a combination of vetiver grass and MICP has the most effective in enhancing the sandy soils' shear strengths, reducing erosion problems.