EVALUATING BIO-CEMENTATION INJECTION TECHNIQUES FOR SILICA SAND: DURATION, DISTRIBUTION, AND STRENGTH ENHANCEMENT

Abstract

Challenges frequently encountered in research on loose sand improvements through the use of microbial-induced calcite precipitation (MICP) include the non-uniformity of cemented products and blocking in the vicinity of the injection pipe. One of the most important factors influencing MICP’s success is the injection method. In this study, three bio-cementation injection methods using Sporosarcina pasteurii bacteria were compared on silica sand samples in the laboratory. The aim was to assess the performance of each injection method in terms of time efficiency, cementation product distribution, and comparison in soil shear strength before and after cementation. The employed injection techniques encompassed direct mixing (DM) injection, two-phase (TP) injection, and modified stage (MS) injection. The findings indicated that none of the three injection methods yielded ideal outcomes in all aspects. The MS injection produced the most cemented volume by 57.5%. However, no strength increases were observed, as evidenced by the hybrid sample’s internal friction angle (φ) of 31.72°, which was similar to that of uncemented sand. Conversely, the DM injection produced the largest improvement in shear strength with a 46.416° φ value, although cementation was limited to the upper half of the sample by 52.4% volume.