Study on the mechanical properties of Yili loess improved by EICP biomimetic mineralization technology under freeze-thaw cycle conditions

• The enzyme-induced carbonate precipitation technique effectively suppresses the initiation and propagation of freeze–thaw-induced soil cracks. • An improvement mechanism of the enzyme-induced carbonate precipitation technique targeting the structural weakness of Yili loess is proposed • The mechanical characteristics of soil improved by the enzyme-induced carbonate precipitation technique under coupled freeze–thaw and confining pressure conditions were clarified. • The feasibility of applying the enzyme-induced carbonate precipitation technique in high-altitude cold regions is validated. This study employs Enzyme-Induced Carbonate Precipitation (EICP) technology on Yili loess to enhance its resistance to freeze–thaw damage. EICP significantly improves the durability of the loess by restricting moisture migration and alleviating stresses induced by ice crystal formation. Following 15 freeze–thaw cycles, specimens treated with EICP exhibited only minor surface cracks, in stark contrast to the extensive crack networks observed in untreated specimens. In terms of mechanical properties, the EICP-treated loess demonstrated a 1.5-fold increase in unconfined compressive strength and a 1.33-fold rise in initial elastic modulus, maintaining advantages of 1.6-fold and 2.2-fold, respectively, after undergoing the cycles. The failure mode shifted from shear to compression, indicating enhanced structural integrity. Under the combined effects of freeze–thaw action and confining pressure, the shear strength of the treated loess consistently remained higher, primarily due to an increase in cohesion (1.17-fold initially and 18.72% higher after cycling), while the friction angle exhibited minimal change. Scanning Electron Microscope (SEM) observations revealed that calcium carbonate cementation filled the pores, resulting in a dense structure dominated by small- to medium-sized pores, effectively suppressing pore expansion and crack propagation induced by freeze–thaw cycles. This research showcases a promising technique for stabilizing Yili loess in cold regions.