Development of biogrouting using plant-derived urease and calcium phosphate compound

摘要

Biogrouting is a new soil improvement methos based on biological processes. Calcium phosphate compounds (CPCs) are commonly used as biogrouting materials. Their solubility of CPC is pH-dependent, with optimal values for extraction at approximately pH 8. Urea hydrolysis is a well- known biological catalyst. It can be induced by urease and releases hydrolysis ions, which can then increase pH. In this study, CPCs and urea hydrolysis were utilized to solidify sand. The urea hydrolysis can be used as a pH regulator for CPCs. Furthermore, urease is ectracted from Momordica charantia seeds. To test this process, the unconfined compressive strength (UCS) of sand samples was measured. The UCS and pH of the sand samples containing a CPC solution, urea, and Momordica charantia seed extract were found to increase. In the sand samples with CPCs and urea hydrolysis, pH was increased by approximately 1.5 and UCS was increased to twice that found in sand samples containing only the CPC solution.This study suggest that CPCs and urea hydrolysis together have the potential to increase the strength of sand materials.