Specialists from the Department of Geotechnics of the Saint Petersburg State University of Architecture and Civil Engineering adapted the method of artificial soil freezing during the construction of a sewer network along the Karpovka River embankment in Saint Petersburg. The work was carried out on the city's most important infrastructure facility: it will stop the discharge of untreated wastewater into the river, which will significantly improve the environmental situation.
The project was attended by the Director of the SPbGASU Geotechnology Science and Production Consulting Center, Corresponding Member of RAACS, DSc in Engineering, Professor at the Department of Geotechnics Rashid Mangushev, Head of the Department of Geotechnics, PhD of Engineering Sciences, Associate Professor Anatoly Osokin, Lead Engineer, Person in Charge of the Project Philipp Kalach and Associate Professor, PhD of Engineering Sciences Vyacheslav Polunin.
The department's specialists provided scientific and technical support for the design of a shaft with a diameter of six meters and a depth of 42.8 meters in the difficult engineering and geological conditions of the city center.
"The construction of a collector is associated with a complex of engineering and geological risks. The key difficulties are weak water-saturated soils, including quicksand. The high level of groundwater complicates dewatering during the development of deep collectors. Restrictions due to historical development and the proximity of the river increase the level of complexity. For the safety of underground construction, we proposed the construction of a borehole shaft protected by a temporary ice-soil barrier obtained by artificially freezing the soil, and regular geotechnical monitoring," explained Philipp Kalach.
Rashid Mangushev specified that the technology of artificial soil freezing makes it possible to create a temporary ice-soil barrier during the construction of underground structures in difficult hydrogeological conditions.
"This technology of artificial soil freezing is especially relevant for the construction of deep mines (up to 100 meters), tunnels and collectors in conditions of high groundwater levels, the presence of weak water-saturated and thixotropic soils. We adapted it to the specific conditions of the facility. During the calculation, the required thickness of the ice-soil barrier, the volume of frozen soil, the refrigeration capacity of the freezing station, the freezing time and the number of required stations are determined. Calculations using this method ensure the reliability and safety of construction and installation work," Professor Mangushev summarized.
“The high qualification of the specialists allowed us to objectively and promptly evaluate the adopted design solutions, inform the general designer about the required additions and justify the technical solutions in the Main State Expertise of Russia,” says the letter of gratitude from Specialized Tunnel Construction LLC, which is carrying out these works on the order of the State Unitary Enterprise Vodokanal of Saint Petersburg, addressed to the SPbGASU Rector Evgeny Rybnov.
