Analysis of maintenance geotechnologies and monitoring
of sewer tunnels in complicated geotechnical engineering conditions

Summary

A comprehensive approach to the selection of geotechnologies for the reconstruction of long sections of sewer tunnels in complicated ground conditions, under technogenic impact and continuous transportation of effluents is described. Based on the analysis of operating long-running sewer tunnels, as well as the results of an instrumental examination of their technical condition, the main factors of technogenic and natural origin that reduce their design safety and sustainable operation of the most loaded sections of the system of sewer tunnels are described. The lack of data on this issue in the regulatory framework and technical literature is noted. The advantages and disadvantages of the applied technologies of sewer tunnel rehabilitation are given. Recommendations and requirements to the rehabilitation of tunnels are proposed depending on the ground conditions, wear rate, section length, dynamics of wastewater transportation.

Key words

operational environment , sewer tunnel , complicated ground conditions , design safety , maintenance geotechnologies , modeling and geomonitoring

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Choosing a technology for repairing sewers operated in difficult soil conditions with account of the geometric irregularity of the tunnel sections

Summary

Long-running sewer tunnels in large cities have a degree of deterioration of up to 55% or more. Difficult engineering-geological and hydrogeological conditions for tunnel laying, as well as intense anthropogenic impacts cause an increase in the defect rate of sewer tunnels. Based on calculations and hydraulic modeling, it is shown that with a high load of sewer tunnel networks and the impossibility to stop completely the transportation of effluents, the primary objective in choosing measures for repair and rehabilitation of tunnels is the search for technical solutions that provide for the maximum wastewater flow after the rehabilitation given the cross-section narrowing and geometrically irregular sections. The successful experience of SUE «Vodokanal of St. Petersburg» in the rehabilitation of sewers with narrowing sections without stopping the transportation of wastewater using technologies that meet these requirements is presented.

Key words

discharge capacity , operation reliability , sewer tunnel , complicated ground conditions , vibration strength , subsidence , cross-section narrowing , repair technology

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Geotechnical support of the zero-defect life cycle of unique sewage pumping stations in complex engineering and geological environments

Summary

For the sustainable development of megalopolises, the sustainable operation of the urban underground engineering infrastructure has been one of the prime factors where the main sewage pumping stations are unique elements. On the basis of the study of extensive pilot and experimental materials, the specific features of the operation of long-term operating head sewage pumping stations built by the method of large-sized coffers in a complex soil environment are analyzed. The results of the long-term monitoring of the technical state of structures are given, the classification of defects and the dynamics of their development are given. Based on the results of modeling the joint operation of the systems «lowerable shell of the pumping station – the inclosing geomass» and results of the experiments, the actual bearing capacity of the structure is predicted, as also preventive geotechnical measures are proposed to ensure the trouble-free life cycle of the underground structure at the pilot wastewater facilities. Geotechnological methods for protecting pumping stations with monitoring support have been developed. A unique experience of practical application of the developed methods at the stages of the life cycle of the head sewage pumping stations at the facilities of the SUE «Vodokanal of St. Petersburg», including design, construction and operation, is presented.

Key words

monitoring , complicated ground conditions , geotechnical protection measures , unique underground wastewater structures , large-sized coffer