In the paper construction specificity of St. Isaak Cathedral’s underground space and engineering geological profile features are considered. The comparative assessment of condition and properties modification of water-saturated quarternary sandy and clay soils during 55 years are taken up (1954-2009). The dynamic of groundwater contamination due to leakage sewers and its aggressiveness are estimated. The researches of microbes activity in soils which are characterized by quasiheavy values are completed. The structural of complex monitoring to secure of St. Isaak Cathedral long-term stability are proposed.
This paper discusses the geobiological and hydrogeochemical processes in St.-Petersburg underground space and their role in corrosion of escalator constructional materials. The special attention were attracted to the ecological conditions which are connected with organic, inorganic contaminants and microbiota transporting to soils and groundwater from leaking sewer system and also from zones of long existing cemeteries. A detailed study and numerical analyses of escalator tunnel constructional materials were carried out to reveal biological defeat and destruction of concrete and grey iron as a result of microbiota destructive activity.
В условиях интенсивного многоуровневого освоения подземного пространства Санкт-Петербурга остро стоит задача прогнозирования и диагностики экзогенных процессов на стадии проектирования, строительства, эксплуатации и реконструкции сооружений. Показана необходимость учета техногенных факторов, таких как химическое, микробное и температурное загрязнение геологической среды, оказывающих влияние на трансформацию состояния и прочности песчано-глинистых пород основания сооружений. Особое внимание уделено влиянию загрязнения коммунально-бытовыми стоками на свойства мореных суглинков и озерно-ледниковых глинистых отложений, которые используются в качестве несущего горизонта для свайных фундаментов и естественного основания для ленточных фундаментов зданий XVIII-XIX веков. Подчеркивается роль агрессивности подземной среды и биокоррозионных процессов в разрушении конструкционных материалов.
The main natural and anthropogenic factors forming the specificity of environmental conditions in the underground environment, which affects the development of deformations and corrosion processes of transportation tunnels, are considered. Natural factors include radon intake, the presence of buried bogs and marshy rocks. Technogenic factors of underground space pollution are household dumps, sewage system leaks, cemeteries. On the example of some transit tunnels it is shown that engineering-geological and hydrogeological conditions, as well as geo-ecological situation determine the peculiarities of functioning of these structures. It is noted that the destruction of tunnel materials occurs mainly due to the biochemical factor.
Within the limits of St. Petersburg, the levels of underground space development have been identified, at each of which the influence of structural-tectonic, engineering-geological, hydrogeological and geo-ecological factors on the manifestation of exogenous processes is considered. The complex influence of natural-technogenic processes on the stability of structures in the underground space of St. Petersburg is considered on the example of the Obukhovo-Rybatskoye tunnels. It is emphasized that the nature and intensity of movements of tunnel structures depend on the state and physical and mechanical properties of the host rocks, hydrodynamic and hydrochemical regime of underground water, as well as gas-dynamic phenomena. The great influence of biocorrosion processes in the destruction of tunnel lining materials has been shown
The reasons for deformations of one of the most important architectural and historical monuments and shrines of St. Petersburg - St. Isaac's Cathedral - are analyzed. The history of the construction of the cathedral, its design features are described, special attention is paid to the arrangement of the foundations of this unique structure. The main natural and technogenic factors which play a negative role in the development of long-term and irregular deformations of the cathedral are considered. It is emphasized that the presence of weak sandy-clay soils and the absence of their filtration consolidation has predetermined the non-stabilized state of the soils at the base of the cathedral. Leaks from drainage systems contribute to active pollution of groundwater and predetermine the reduction of strength and strain properties of soils. The composition of ground waters indicates active leaching of dolomitized limestones of the Putilovskaya plate, which were used in the construction of the foundations. The made calculations showed that the foundation of the cathedral works in the stage of plastic deformation, accompanied by catching of grounds from under the foundations. The calculations of the maximum and average values of settlements on the basis of consideration of soils as linear and nonlinear medium have been made. It is shown that the most rational means of protection to prevent the development of further deformation of the cathedral is the "wall-in-soil" construction.
At present, when assessing the geo-ecological conditions of the city territory, the existence of buried marshes is not given proper attention. It is known that by the time of laying the city 75% of its area was boggy. Complete removal of boggy deposits was carried out only when their thickness does not exceed 3 m. Deeper marshes and swampy areas turned out to be buried and continue to “live”, being the most active geo-ecological element of the city's underground environment. Although swamp waters outside the zones of technogenic pollution are characterized by low salinity and mainly hydrocarbonate-sodium, less often calcium composition, they play a significant role in the formation of physical, chemical and biochemical environment of the underground space of the city. In such watered sections containing boggy sediments, sharply pronounced reducing conditions are noted. In addition, there is an activation of microbiological activity at considerable depth, since bog sediments contain a variety of physiological groups of microflora. Swamp sediments serve as an active natural sorbent for heavy metals, as well as a number of organic pollutants. On the one hand, the microbiological activity and diversity of bog biocenoses leads to the destruction of organic pollutants. On the other hand, the activity of the biotic component is usually accompanied by biochemical gas generation. The formation of methane, nitrogen, hydrogen sulfide, carbon dioxide, etc. is observed in the underground space of St. Petersburg. Low-soluble gases (methane, nitrogen) will affect the stress-strain state of sandy-clayey rocks, contributing to mudbursts, and in the presence of methane - spontaneous combustion. Soluble and highly water-soluble gases usually form a corrosive environment in relation to metals, concrete and other building materials. Studies of the impact of buried bogs on the environmental condition of the city performed in SPGGI allowed to identify and delineate zones with the highest level of negative processes that determine the safety of development and use of the underground space of St. Petersburg.