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

Mobile diagnostic package for the inspection of tunnel sewers

Summary

To maintain the wastewater disposal systems in proper working order and prevent from emergency situations regular inspections of tunnel sewers shall be carried out. For safety considerations technical inspections are usually carried out at night when the tunnel fill is minimal. However, there are sections that are difficult to inspect because of almost complete fill and impossibility of their temporary cutoff. It is impossible to guarantee detecting all the defects in the tunnel submersed section inspected. This predetermined the necessity of the systematic approach to efficient and comprehensive monitoring of the technical state of tunnel sewers; to the development and introduction of an automated system with the use of advanced hardware environment, numerical procedures and information systems. The mobile diagnostic package for the inspection of tunnel sewers developed by the experts of St. Petersburg Vodokanal is described. The presented equipment provides for obtaining reliable information on the state of both the above-water and submersed parts of the sewers. Inspection is carried out without cutting off sewers; at that the presence of workers in the tunnel is not necessary. The equipment is installed on the truck chassis. The mobile diagnostic package provides for building up the data base of the tunnel sewer state; determining maintenance and repair priorities.

Key words

wastewater , monitoring , tunnel sewer , mobile diagnostic package , sewer defects , operational parameters

Development of the tunnel sewerage in Saint-Petersburg

Summary

The information on the construction of a tunnel sewer system for the improvement of the environmental situation in Leningrad-Saint-Petersburg and the Gulf of Finland drainage area is presented. A short description of the tunnel sewers in Saint-Petersburg, the conditions of their construction, the arrangement of maintenance and operation, safety arrangements during tunnel inspection are given. In 1947 «Podzemkanalstroi» Trust was established with the purpose of tunnel construction. The projects of tunnels were designed by «Lengiproinzhproekt» Institute. The research workers of the Leningrad Civil Engineering Institute – St. Petersburg State University of Architecture and Civil Engineering developed the methods of hydraulic calculations, separate tunnel in-line structures designs, methods of the sewer protection from corrosion, repair and rehabilitation. The operation and maintenance of tunnel sewers is carried out by the special subdivision – Tunnel Sewer Operation District that was established on December 1, 1978. The objective of this subdivision is the acquisition of complete information on the integrity of all the tunnel sewers in the city and their structures (shafts, bore holes, chambers etc.); management of routine maintenance and operation; inspection and accumulation of the information on the dynamics of the integrity changes of the structures. The inspection results provide for identifying the causes of the deterioration of tunnels and their structures; determining the priorities and repair and rehabilitation measures, improving the reliability of the municipal wastewater disposal system.

Key words

tunnel sewer , Tunnel Sewer Operation District , protection from deterioration , technical inspection of tunnels