Link for citation: Polovnikov V.Yu., Volynin A.F. Geophysical and thermal analysis of soils in the zones of location of sewer collectors in St. Petersburg. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2022, vol. 333, no. 5, рр.81-88. In Rus.

The relevance of the research is related to the normative functioning of the sewer systems of cities and industrial enterprises. This is the key to ensuring environmental safety. On sewer collectors located in the central, northern and eastern parts of St. Petersburg, emergency situations occurred with the release of quicksand into the collector during construction (Faberge Square, Neva River embankment) or during operation with the formation of a large funnel (Rizhsky Avenue). Above the sewer collectors, passing along the embankments of the Fontanka River, the Griboedov Canal and the Moika River, there were soil failures and numerous subsidence of the road surface. As a result of geophysical work in these areas, quicksand soils were found, which are characterized by very low electrical resistivity (less than 3 Ohm·m). Such electrical resistivity has not previously been noted for the soils that make up the geological section of the Quaternary deposits of the city. The main aim of the study is geophysical and thermal analysis of soils in the domains of placement of sewer collectors in St. Petersburg, located at the sites of accidents. The object of the research is a sewer collectors in St. Petersburg, located in the places of accidents with the release of quicksand. Methods. Geophysical work was carried out using the method of electrotomographic measurements on 18 profiles along the collector routes and perpendicular to them and by the method of spectral seismoacoustic profiling along four profiles, combined with electrical survey profiles. Numerical analysis of heat and mass transfer was executed with rational values of the grid parameters and the time integration step. The assessment of the reliability of the results of the work was carried out by testing on the example of heat transfer problems, the numerical methods used and elements of the developed algorithms for solving boundary value problems of heat and mass transfer, checking the conservatism of difference schemes, and comparing with the known data. The finite difference method and the implicit difference scheme were used. The peculiarity of the problem solving was the discontinuity of the thermophysical characteristics at the contact boundaries between the layers and the use of a combined coordinate system. Results. A geophysical study and analysis of the temperature fields of the soil in the areas of the sewer collectors of St. Petersburg, located in the places of accidents, were carried out. A significant influence of the sewer collector on the temperature distribution in the zone of its location is shown. The possibility of development and reproduction of bacteria of the psychrophilic group in places where sewer collectors are laid has been theoretically confirmed.