Microbiological Improvement of the Physical Properties of Soil

The application of microbiological processes for improvement of the physical properties of soils offers the promise of sustainable, cost effective, non-disruptive ground improvement for a variety of geotechnical problems. Potentially beneficial applications of microbiological processes include increasing the stiffness of soil to reduce settlement and lateral deformations, increasing shear strength to enhance foundation bearing capacity and slope stability and to facilitate excavation and tunneling, reducing the susceptibility of granular soil to earthquake-induced liquefaction, reducing swell (expansion) potential of fine grained soil, and reducing permeability for groundwater control. Microbiological processes that can potentially be employed for these applications include mineral precipitation, mineral transformation, and growth of biofilms and biopolymers. These processes are known to improve the engineering properties of soil 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 the effects undesirable (e.g. clogging of water treatment plant filters). The engineering challenges in developing beneficial applications of these processes involve identifying the appropriate microbial processes to achieve the desired effect and inducing the desired process (or processes) over a time frame of engineering interest in the location of interest. If these challenges can be met, microbiological improvement of the physical properties of soil may transform some aspects of ground improvement in geotechnical practice