A New Framework for Identifying Cementation Level of MICP-Treated Sands: Fid-Bau Portal

A New Framework for Identifying Cementation Level of MICP-Treated Sands

Nafisi, Ashkan / Montoya, Brina M.

Microbial induced calcium carbonate precipitation (MICP) is a ground improvement technique that can be employed to increase soil stiffness and shear strength. Based on the treatment’s objectives, soil properties are improved to reach different levels of cementation. Shear wave velocity and mass of calcium carbonate can be used to categorize treated soils into various levels of cementation. However, the obtained results show that these two parameters are not sufficient in categorizing cementation and may be misleading. Therefore, a new framework which considers particle size, the dependency of shear modulus on confinement, shear wave velocity, and calcium carbonate content is proposed. In this paper, three types of poorly graded sands with different particle sizes were used. Shear modulus was measured at varying levels of cementation and confinement pressures to find out the amount of dependency of small strain shear modulus on confining pressure. According to the results, the finest soil needs more calcium carbonate to reach heavily cemented level, but the final shear wave velocity is lower compared to the coarser sands. Based on the obtained results, n (the slope of log G_max against log of mean effective stress) values for lightly, moderately, and heavily MICP-sands are about 0.4, 0.3, and less than 0.1, respectively.