Data contained in requirements documents concerning recommended methods of loads calculation on tunnel linings and results of field studies of stress-strain state of the system «tunnel linings – rock» obtained during geotechnical monitoring when tunnels were constructed in various geological engineering conditions were considered in this paper. Recommendations about using methods of calculation on the basis of roof arch are provided by requirements documents regarding calculation of tunnel linings; at the same time natural stress field and stress-train performance of soil body, which influence to a great extent on stress-strain state of linings and supports are usually not taken into account. According to the results of field studies that were led in the framework of geotechnical monitoring during transport tunnels construction using technologies providing avoidance of tunnel face front and tunnel contour displacements, soil continuity is preserved and thus, a possibility of aching is avoided. Also this concerns water-saturated quaternary deposits during construction of running and escalator tunnels of underground rapid transit system of Saint-Petersburg with the help of hydraulic and earth-pressure balance-tunnel boring machines. In many cases of tunnels construction for different purposes when soil body displacements do not influence on continuity the calculations of linings and supports should be made with the help of continuum mechanics methods.
Everywhere in Saint Petersburg the top strata are represented by quaternary deposits, and the ground water level is approximately 2,5 m down from the surface. Below the quaternary deposits, at depths of 40 to 60 m, are Cambrian (Proterozoic) clays. There are many ancient buildings of a historic and architectural value on the day surface that cannot tolerate day surface settlements. The construction of underground stations, and especially inclined escalator tunnels, causes surface settlements. Technologies of construction of escalator tunnels and station tunnels have been developed in Saint Petersburg to minimize such day surface settlements.
The intelligent technology of designing of the constructions of pillar underground station is adduced. Station is building with applying of low-settle technology, which takes into consideration main stages of the building process. The scheme of interaction of the system «support lining-soil massif» was accepted as basic scheme of calculations. The calculations of the stress-strain condition of constructions was performed with applying of finite-elements method.
An advanced method of ultra-wide band electromagnetic ground penetrating probing has been developed. This method enables the running of geological probing measurements from both the surface of the land and the boring face during construction of tunnels up to a depth of one hundred meters, and in special cases, even deeper. Portable equipment of low weight is used for these underground radar measurements. Total weight is not more 15 kg. Time of geological cut measurement and its data processing is approximately 3 hours for probing depths of about 70 m.
The results of long-term studies of the stress-strain state (SSS) of structural elements of St. Petersburg subway stations are presented. The obtained data indicate the continued growth of stresses on the linings during operation. At steady mountain pressure at the end of the observations, the redistribution of the stress state in the cross section of the stations continues.
