Experimental optimization of biocement formation: alternative countermeasure for surface erosion of cut slope

Abstract

The research w o r k aims to assess the feasibility of i n t r o d u c i n g the microbial induced carbonate p r e c i p i t a t i on (MICP) as an alternative technique for surface stabilization of the cut slopes by augmenting potential indigenous ureolytic bacteria. A set of column solidification tests was conducted on embankment soil (Hokkaido expressway, Japan) to optimize the performance of bacteria regarding bacterial population of culture solution (optical density (OD600) from 1 to 6), and concentration of Ca^* and urea i n cementation solution (0.5 m o l / L and 1 mol/L) at the temperature of 20°C. The UCS of treated samples was estimated using needle penetrometer, and the microstructure of the treated specimens was observed using scanning electron microscope (SEM). The results reveal that the UCS of the specimen increases w i t h increasing ODeoo w i t h o u t any clogging w i t h i n the samples. Treating the soil using 1 m o l / L concentrated (Ca2+ and urea) cementation solution and bacterial culture w i t h ODeoo of 6 results the highest UCS of 7.5 MPa while achieving relatively a homogeneous solidification along the column profile. The micrographs of the treated specimen confirms that the rombohedral calcium carbonate crystals formed w i t h i n the pores of soil matrix, w h i c h has effectively bonded the adjacent soil particles, and contributed to enhance the strength significantly at the o p t i m i z e d treatment condition.