Evaluation of wind erosion resistance of EICP solidified desert sand based on response surface methodology

Wind erosion is the primary cause of land desertification in arid and semi-arid regions. Enzyme-induced carbonate precipitation (EICP) will produce a solid coating on the surface of desert sand that inhibits wind erosion. Three critical variables for EICP treatment, including enzyme-cementation ratio A, cementation solution concentration B, and spraying volume of reaction solution C, were evaluated with three wind erosion-resistance indexes (surface strength, calcium carbonate content, and solidified layer thickness) of desert sand, and further optimized with the response surface methodology (RSM). The mass loss of the EICP-treated desert sand was studied by wind tunnel tests with wind speeds of 8-14 m/s and erosion times of 0-30 min. Material composition and microstructure of the EICP precipitates were investigated with X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Results indicate that the three wind erosion-resistance indexes tend to rise with greater A and B values followed by a decline while monotonically increasing with C but the increments decrease when C>5 L/m(2). The optimal solidification effect was reached when A=1.082:1, B=1.282 mol/L and C=8.70 L/m(2), which corresponds to a maximum wind speed of 14 m/s for solidified desert sand. Large amounts of calcite crystals were produced in the EICP-treated sand and filled soil pores. The particle contacts transform from point contact to surface contact and the enhanced particle bonding induces a more compact soil skeleton. The above experiment evidence corresponds to increased surface strength and wind erosion resistance. The results of this study will provide an experimental foundation for the application of EICP technology to enhance wind erosion resistance of desert sands.