Hydraulic property improvement of MICP-treated loess: Macroscopic performance and microscopic mechanism

Microbial induced carbonate precipitation (MICP), an innovative soil stabilization technique, has recently emerged as a promising method for mitigating loess erosion. This study investigates the hydraulic properties of MICP-treated loess through comprehensive laboratory tests. The disintegration tests were conducted to evaluate the water stability of MICP-treated loess under different curing days ( C d ) and cementation reagent concentrations (C RC s ). Results show that the disintegration ratio shows a 57.4% reduction with C RC s = 1.0 M, C d = 14 d treatment and also the disintegration process is prolonged accordingly. Subsequently, double-line method was applied to investigate the water sensitivity of MICP-treated loess. The collapsibility coefficient of the loess sample after MICP solidification can be reduced by 23.8%. The permeability coefficient of MICP solidified loess can be effectively decreased up to two orders of magnitude after MICP treatment. A quasi-two-dimensional model test apparatus was fabricated to perform infiltration and capillary rise experiments, aiming to characterize the permeability and water retention capacity of MICP-modified loess under laboratory conditions. The spatiotemporal variation of water content and the capillary height, the wetting frontal profile were also characterized. X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) analyses were performed to identify the precipitated mineral and reveal the bonding mechanism. Mercury intrusion porosimetry (MIP) tests were further implemented to characterize the pore size distribution and interpore connectivity of MICP-treated loess. This study provides a theoretical basis for the water-resistant protection of loess slopes and foundations in loess areas.