Abstract: Granite residual soil is rich in hydrophilic minerals and exhibits strong water sensitivity; it tends to soften and disintegrate upon wetting. It is a soil type commonly associated with geohazards such as landslides. Urease-based biomineralization is an environmentally friendly soil-improvement approach that enhances resistance to disintegration of granite residual soil. However, granite residual soil generally has small pore size and low permeability, and its effective biomineralization depth is shallow using conventional spraying biotreatment solution in-situ. This study proposes using a urease-based, low-pH biotreatment solution for the biomineralization of granite residual soil. The effective biomineralization depth was evaluated, and the underlying mechanisms were elucidated using calcium carbonate content measurements, disintegration tests, and scanning electron microscope (SEM) analysis. The test results show that the urease-based low-pH biotreatment solution can significantly improve the effective biomineralization depth of granite residual soil. The biotreatment solution prepared with pH = 3.00 cementation solution and soybean urease solution at a 1:1 volume ratio has the best biomineralization. For granite residual soil with an initial water content of 24%, the effective biomineralization depth reaches 40 mm.

Key words: biomineralization, granite residual soil, urease-based low pH biotreatment solution, anti-disintegration, effective biomineralization depth