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.
The paper presents the results of field observations on formation of stressed state in shotcrete temporary tunnel support when constructing a traffic tunnel of NCRW near the slope. Numerical simulation of stressed deformed state of the «support – block» system has been accomplished for the considered engineering geological conditions. The results obtained point to a possibility of developing the procedure of calculating supports based on results of field observations under comparable conditions in combination with SDS modeling applying finite-element method adapted for specific conditions.
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 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.
The results of long-term studies of the stress-strain state (SSS) formation of the St. Petersburg subway lines are presented. The data obtained testify to the continuing growth of loads on the linings during operation. The source of load growth is vibration, which is transmitted to the outer contour of the lining and contributes to the vibration compaction of the soil mass.
The process of load formation on the tunnel lining can be generally represented as a curve, in the character of its development there are three components reflecting the influence of the face and the contact conditions between the lining and the massif, depending on the technology of its construction. The magnitudes of the loads depend on the distance from the tunnel face, at which the lining comes into contact with the rock mass and the condition of continuity of movement of tunnel contour and lining will be satisfied. The task of determining the loads on the lining is solved from the condition of joint deformation of the lining-soil massif system. The elastic model of interaction between the lining and the rock mass according to G.N.Savin is considered. When the lining interacts with the rock mass, the lining does not interact with the massif instantaneously, but at a certain distance from the bottom hole. In order to approximate the calculated values of loads to the actual ones, it is necessary to take into account the bottom hole influence. The solution of the interaction problem is reduced to the contact problem - the problem of continuum mechanics. The deformation modulus is replaced by the reduced modulus. The proposed method of calculation of loads on tunnel linings has been programmatically realized in the DELPHI for Windows environment. The program allows to make two-dimensional and volumetric interpretation of the computational data and to output the results of the program's work to the printer.
