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.

No abstract

The paper offers a complex approach to assess underground space as a multi-component system for its development and utilization. It is indicated that a geotechnical analysis of sandy and clayey soils of St. Petersburg needs to be carried out based on two models, i.e. one for a jointed and blocky environs and the other for fine-pored media. It has been established that chemical composition of the ground water in the city is characterized with a high content of alkaline-earth elements, which proves the intensive destruction of construction materials, as well as with presence of organic substances judging by the chemical oxygen demand (COD) and biological oxygen demand in 5 days (BOD5). For the first time ever, a microbiotic component has been distinguished which determines the following phenomena: 1) alteration of physical and mechanical properties of sandy and clayey soils; 2) development of flowing sand and thixotropic phenomena; 3) biocorrosion of various construction materials. It is stated that even consolidated morainic soils usually viewed as a safe foundation and media for structures of various applications are transformed into weak and easy-deformable materials characterized with low strength in conditions of intensive contamination.

No abstract

The underground space of the Kupol deposit is analyzed as a multicomponent system – rocks, underground water, microbiota, gases (including the mine atmosphere) and supporting structures – metal support and shotcrete (as an additional type of barring) and also stowing materials. The complex of host rocks is highly disintegrated due to active tectonic and volcanic activity in the Cretaceous period. The thickness of sub-permafrost reaches 250-300 m. In 2014, they were found to contain cryopegs with abnormal mineralization and pH, which led to the destruction of metal supports and the caving formation. The underground waters of the sub-permafrost aquifer are chemically chloride-sulfate sodium-calcium with a mineralization of 3-5 g/dm3. According to microbiological analysis, they contain anaerobic and aerobic forms of microorganisms, including micromycetes, bacteria and actinomycetes. The activity of microorganisms is accompanied by the generation of hydrogen sulfide and carbon dioxide. The main types of corrosion – chemical (sulfate and carbon dioxide), electrochemical and biocorrosion are considered. The most hazardous is the biocorrosion associated with the active functioning of the microbiota. Forecasting and systematization of mining and geological processes are carried out taking into account the presence of two zones in depth – sub-permafrost and below the bottom of the sub-permafrost, where mining operations are currently underdone. The importance of assessing the underground space as a multicomponent environment in predicting mining and geological processes is shown, which can serve as the basis for creating and developing specialized monitoring complex in difficult engineering and geological conditions of the deposit under consideration.