The dissertation is devoted to the development of the scientific idea of controlling the stress-strain state of vertical excavation (hoisting shaft). Controlling is conceptually understood as the ability to predict changes in stresses and strains of the system "temporary fastening – lining – the surrounding array" when changing the types of lining. The relevance of research in this area is justified by the need for scientific substantiation of the parameters of construction of vertical excavations (hoisting shaft) with increasing volumes of underground construction, including metro in the Dnipro and Kyiv.
The process of controlling the stress-strain state of vertical excavation is realized by generalizing the results of numerical analysis of different states in the process of soil freezing or creating a construction of bored secant piles and their subsequent extrapolation to different variants of vertical excavation. The basis of controlling is the regularities of the stress-strain state of the hoisting shaft structure, and the search for them is the purpose of the dissertation.
To achieve this, the dissertation analyzes the state of research, considers the specifics of the construction of metro in Ukraine and the features of analytical, experimental and numerical approaches to finding regularities of stresses and strains of vertical excavations.
Based on the results of critical analysis, the numerical approach was chosen as the one that is most adequate for finding the regularities of the stress-strain state. Finite-element models of hoisting shafts being constructed during the construction of the Dnipro and Kyiv metro were created, each allowing to vary the types of linings (reinforced concrete blocks, tubes made of gray cast iron and tubes made of modified gray cast iron), diameter of bored secant piles and different temperature properties.
On the basis of the created finite-element models the numerical analysis of the mine shaft fixed by bored secant piles with variation of their diameter was carried out. According to the results of the analysis, for the first time regularities of displacements and force factors with a high level of approximation (R2 = 0.992 … 0.999) are obtained, which are second-order polynomials, except for the regularity of bending moments along the X axis, which is linear. These regularities characterize the scientific novelty of the dissertation.
During geodetic monitoring of the vertical excavations construction of the Dnipro metro horizontal and vertical deformations of the lining of hoisting shaft 16-bis were measured, the values of which reached 1 … 2 mm. Comparison of these data indicates a match with the horizontal deformations obtained during the numerical analysis of the hoisting shaft № 16-bis, in which the deformations are 1…2 mm, with a maximum value of 2.57 mm in the area of reinforced concrete belts No 7-9.
Using the created finite element models, for the first time the regularities of the stress state components from the modulus of elasticity of frozen soil and the modulus of elasticity of the lining of hoisting shaft were obtained, which are polynomials of the second degree with a high level of approximation (R2 = 0.964 … 0.999). The obtained regularities constitute the scientific novelty of the dissertation. Spatial surfaces are constructed, which, when solving direct or inverse problems, allow to control the stress-strain state of the lining of vertical excavation, which is the practical significance of the dissertation.
During numerical analysis, the regularities of the stress state of vertical excavation in violation of soil freezing technology are obtained, which show that the processes of uneven freezing or thawing increase the stress in the lining by 1.1 … 1.5 times, so they should be considered when designing vertical excavations.
