Impact of microbial activity on soil properties

There are microorganisms in soils and their activity can have a positive or negative impact on soil properties and groundwater. The positive effect of microorganisms includes the self-purification and self-regulation of contaminated groundwater and soil. The negative effect on soil is the change in grain-size composition; the weakening of engineering properties of soils; and the development processes, such as biogas generation, microbial quick-sand formation, and soil liquefaction. This paper addresses the negative effects of microbial activity on soil. Research on the impact of microbial activity in an underground space has been motivated by observations associated with underground infrastructure, such as subway tunnels, utilities tunnels, deep mines including those with tailings, and infrastructure with shallow and deep foundations. An overview of microorganisms in soil and an analysis of microbial activity in soils under the influence of natural and human-made factors are presented. Field and laboratory experiments show the significant impact of microbial activity on the engineering properties and consistency of the soil. Due to the complexity of the process, a study of microbial activity in the soil profile requires an integration of microbiology, biochemistry, engineering geology, and geotechnical engineering knowledge and experience.