Underground Space of Saint-Petersburg as a Multicomponent System: Engineering Geological and Geotechnical Aspects of its Development

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.