Influence of shear strength parameters on loose fine sand treated with coir fiber and microbially induced calcite precipitation

In recent years, there has been an increasing use of Microbially Induced Calcite Precipitation (MICP) technology in ground improvement. Adding fiber to bio-cemented sand leads to significant improvements in its properties. This paper examines how coir fiber and microbially induced calcite precipitation (MICP) might be used to improve the engineering qualities of fine sand. The sand was mixed with Coir fiber at varying Fiber Contents (FC) of 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% by weight of sand. Additionally, varied Aspect Ratios (AR) of 45, 90, 136, 182, and 227 were considered. The mixture also included urease-producing bacteria (Sporosarcina Pasteurii), as well as solutions of urea and calcium chloride with 3M molarity. The untreated and treated sand samples were submitted to a Direct Shear Test (DST). The study found that the shear strength parameters, such as the angle of internal friction, increased by 1.1 times compared to standard fine sand. Additionally, the angle of internal friction (ϕ) of fiber-reinforced sand with MICP showed 1.4 times increase, while the cohesion values demonstrated a sixfold increase compared to MICP fine sand. It was determined that the optimal aspect ratio was 182, and the optimal fiber content was 0.3%. Moreover, the Scanning Electron Microscope (SEM) was utilized to examine the calcite formations present in the treated sand samples, and calcite precipitation was observed between the pores of the soils.