Geotechnical and geoecological fundamentals of sustainable life cycle of unique long-operated underground structures of water disposal systems in difficult soil conditions (the experience of St. Petersburg)

Intensive development of megacities causes the need for sustainable operation of underground urban infrastructure facilities. Unique long-operated underground structures of water disposal systems, which are the facilities of an increased responsibility and danger, are needed for special protection against man-made impact. The paper presents the experience of studying the underground wastewater facilities operation in conditions of weak soils and intensive external static and dynamic impacts, as well as new methods for diagnosing their technical condition, modeling and monitoring the joint work of the “underground structures—soil bulk” system, forecasting and shaping the sustainable life cycle conditions. Single and linear wastewater objects of St. Petersburg are developed and implemented according to the unique geotechnology (at a depth of 70 m), providing simultaneous increase of bearing capacity, operational reliability and ecological safety of long-operated underground wastewater facilities in difficult soil conditions with increasing man-caused impacts.