Abstract:

【Objective】This study aims to advance the application of microbial-induced carbonate precipitation (MICP) in soil and water conservation, it is essential to understand bacterial solution distribution and reinforcement effects. This study proposes a method for indirectly testing the uniformity of bacterial distribution in sand samples, providing a reference for future research.【Method】A one meter long sand column was injected with Sporosarcina pasteurii, and MICP grouting tests were conducted on standard sand. The study compared bacterial solution distributions and reinforcement uniformity with parallel samples and analyzed how bacterial injection methods and the grouting process affected these factors. 【Result】Direct injection of the bacterial solution and alternate injection methods resulted in a more uniform initial distribution of bacteria in the sand column, which could be indirectly evaluated by the urease activity of the bacteria. The subsequent grouting process changed the distribution of bacteria in the sand column. The influence of the fixative solution on the uniformity of the bacterial distribution was small at a flow rate of 4 mL/min, but the washing effect of the cementing liquid on the uniformity of the bacterial distribution was obvious, resulting in significant differences in the unconfined compressive strength and calcium carbonate production of each section of the sand column. 【Conclusion】Testing the urease activity of stirred water solutions in sand samples containing bacteria is a reliable method for indirectly measuring bacterial distribution. The uneven phenomena generated during consolidation are mainly caused by the grouting of cementing liquid. Therefore, direct and alternate injection methods achieve a more uniform reinforcement effect.

Key words: conservation of water and soil, cemented sand, bio-grouting, bacterial distribution, uniformity of reinforcement