Enzyme-Induced Carbonate Precipitation (EICP) for Erosion Control in Sandy Soils with Fines: A Multi-Scale Experimental and LiDAR-Based Quantification Study

Abstract

A multi-scale experimental and LiDAR-based quantification study was conducted to evaluate the effectiveness of enzyme-induced carbonate precipitation (EICP) to mitigate soil erosion. EICP is an emerging biogeotechnical soil improvement technique that improves the mechanical properties of soil by precipitating CaCO3 via hydrolysis of urea in the presence of calcium ions, catalyzed by the urease enzyme extracted from plant sources. The precipitated calcium carbonate cements soil particles together, increasing strength, stiffness, and dilatancy. Laboratory experiments were conducted on manufactured sandy soils with varying fines content to examine the hydraulic properties of treated soil with an optimized EICP recipe. The study included testing soil water characteristic curves, measuring saturated hydraulic conductivity, and estimating unsaturated hydraulic conductivity functions. Furthermore, the compaction characteristics and the unconfined compression strength of the EICP-treated soils were compared to the untreated soils and the soils treated only with CaCl2 to distinguish the influence of unreacted CaCl2 in EICP treatment. The effectiveness of EICP was further evaluated for clayey-sands using a large-scale rainfall simulator with high-resolution LiDAR-based quantification methods on soil surfaces tilted at 20 degrees under three different rainfall intensities. Treatment methods included EICP spray application and EICP mix-and-compact followed by spray. The results demonstrated that the EICP treatment altered the hydraulic response of the soil, improved the compaction characteristics and strength. However, the effectiveness of the treatment decreased with increasing fine content. The EICP treatments significantly reduced the overall erosion potential, with reductions ranging from 57% to 7%.