| The application of microbiological processes for improvement of the physical properties of soils offers the promise of sustainable, cost effective, non-disruptive solutions for a variety of geotechnical problems. Successful development and implementation of microbiological processes for ground improvement would have wide application to a variety of important geotechnical problems, including increasing shear strength and stiffness to enhance foundation bearing capacity and reduce associated settlements, mitigating the susceptibility to earthquake-induced liquefaction, reducing the swell potential beneath foundations and roadways, increasing shear strength to enhance slope stability, cementing soil to facilitate excavation and tunneling and to control soil erosion and scour, and reducing permeability for reducing under-seepage of levees and cut-off walls. Applications of microbiological processes may be especially useful near or beneath existing structures, where the application of traditional soil improvement techniques is limited because of the ground deformations and/or high cost associated with current technologies.;Microbiological processes that can be potentially employed for soil improvement include mineral precipitation, mineral transformation, and biofilms and biopolymers. Many of these processes are known to improve the engineering properties of soils on a geological time scale, and some of these processes are known to induce potentially beneficial effects in shorter time frames but in situations where the context renders these effects undesirable (e.g. clogging of treatment plant filters). The engineering challenge is to induce the desired process over a time frame of engineering interest in the location of interest.;Research at Arizona State University (ASU) on microbiological processes for soil improvement includes performing laboratory experiments to establish technologies for a number of candidate mechanisms, ultimately leading to field tests for mechanisms that look promising. The study presented herein includes a review of literature in microbiology, geology, and geotechnical engineering to identify potentially applicable microbial mechanisms to improve engineering behavior of soils and bench scale experiments to explore feasibility of one of the candidate microbial cementation mechanisms, denitrification. The results from the bench scale experiments suggest that microbial denitrification can be used to improve shear strength of granular soils and has the potential to become a sustainable and cost-effective ground improvement technology in granular soils. |
