Research on the mechanical properties of loess solidified via enzyme induced calcium carbonate precipitation (EICP)

Loess has a special structure that usually leads to collapse, disintegration and dissolution, and easily triggers slope instability, foundation settlement, and ground fissure. As a recently developed soil stabilization method, high efficiency is widely recognized as a fundamental characteristic of Enzyme-induced calcium carbonate precipitation (EICP). Cost-effectiveness and environmental friendliness render it a proper method for fine-grained soil solidification. Based on the orthogonal test method, the role of enzyme concentration within the generalization processes was assessed via specifically designed enzyme-induced carbonate precipitation (EICP) tests. The experiments mandated precise regulation of cementing solution and skim milk powder concentrations, pH value, standing time on the CaCO 3 content, and determining the optimal mineralization condition. Furthermore, to quantify the mechanical performance, the unconfined compressive strength (UCS) tests were conducted to considering the effect of dry density ( ρ d ), cementing solution content (CSC), enzyme to cementation solution ratio (ECSR), and Na-Mt content ( C N ). The test results indicated that the optimal EICP mineralization condition was that the soybean powder concentration was 200 g/L, cementing solution concentration was 1.50 mol/L, skimmed milk powder concentration was 2 g/L, pH was 7, and standing time was 120 h. For the EICP treated loess, the stress-strain curve is divisible into a slow ascending stage, a fast-growing stage, a slow growth stage, and an attenuation decrease stage. A maximum UCS was achieved at the dry density of 1.55 g/cm 3 with 4% Na-Mt content, following a trend of increasing strength concurrent with rises in both initial dry density and Na-Mt concentration. The UCS exhibited the trend of increased firstly and decreased subsequently with the increase of CSC and decreasing of ECSR, it reaches the maximum when the CSC was 14% and the ECSR was 2:3. The research results can promote the practical implementation of EICP method in foundation treatment.