Geotechnical and technological aspects of ensuring the safety of tunnel sewers under the conditions of loose ground of Saint-Petersburg

Summary

Intensive development of metropolitan cities calls for the sustainable operation of the municipal underground infrastructure facilities. Special protection is needed for tunnel sewers of long-term serviceability. Both external and internal factors can influence accidents on sewers. Among the causes of sewer deterioration the following can be identified: sewer trough wear, physical and mechanical structural damages caused by external factors and impact of chemically aggressive wastewater. However, corrosion processes in sewers pose the key problem. The main specific feature of the big sewer operation is the process of microbiological (gas) corrosion of concrete and fittings as well as the technical equipment of the shafts. The defect symptoms are presented together with the new methods of tunnel sewer diagnostics based on the sophisticated materials of their operation under the conditions of loose ground and intensive man-induced impact. The geotechnological methods of protecting tunnel sewers of long-term serviceability have been developed. The unrivalled experience of using these methods at the St. Petersburg facilities with monitoring support is presented. The system of sewer testing has been developed; the basic methods of protection against deterioration have been presented. The most widely used methods of tunnel sewer protection in Saint-Petersburg are so called passive. They are based on the advanced choice of corrosion-proof materials in direct contact with corrosive media. The importance of combined geotechnical and internal monitoring of tunnel sewers is shown.

Key words

monitoring , corrosion , tunnel sewer , man-induced impact , geotechnical and technological methods of protection

Specific features of inspecting and innovative methods of protecting sewer tunnels in operation for a long time in unstable soils under increasing technogenic impact

Summary

An important factor in ensuring the technospheric safety associated with the increasing technogenic impact with the intensive development of megalopolises is the stability of the operation of urban underground engineering infrastructure utilities. Sewer tunnels that have been in operation for a long time in unstable soils, need special protection from man-made impacts. On the basis of the study of pilot and experimental materials, the features of the operation of deep sewer tunnels under conditions of soft soils and intense technogenic impacts are analyzed. New methods of diagnostics, defect symptoms and the results of modeling the combined action of systems «sewer tunnel – enclosing geoarray», as well as the experimental data at pilot facilities are presented. Geotechnological methods have been developed to protect long-term operating sewer tunnels. A unique experience of applying the developed methods at the facilities of St. Petersburg with monitoring support is presented. The proposed special methods for assessing the integrity health, the geomonitoring system and geotechnical methods for protecting sewer tunnel structures including the technologies for structural reinforcement and rehabilitation in conditions of wastewater transportation, provide for improving the bearing capacity of structures and their operational reliability in difficult soil conditions under increasing technogenic impact.

Keywords

monitoring , method of studying , man-induced impact , sewer tunnel structures , severe engineering-geological environment , geotechnical protection measures