Sediments of an underwater tunnel constructed by the immersed sections method

Abstract

In St. Petersburg there is a necessity to build a large number of underwater tunnels for various purposes. The construction of tunnels using the method of immersed sections is the most complex and high-tech, but at the same time competitive construction method, requiring the solution of a non-standard engineering task at each stage. The aim of the study is to analyze the sediment of the immersed tunnel section depending on the deformation characteristics of the underlying sand covering and the different depth of the bedrock of the Proterozoic clays. The calculations were completed using mathematical 3D models in the MIDAS GTS NX software package based on the finite element method. The reliability of the mathematical modeling results was confirmed by high convergence with the results of field observations of section precipitation during the construction of the Kanonersky Tunnel. The obtained results were statistically processed by methods of correlation and regression analysis with the construction of functional dependence. The greatest contribution to the change in the sediment of the tunnel section was made by the thickness of the Quaternary soils at the base of the section – the depth of the Proterozoic clays, with significantly less influence of the stiffness of the underlying sand covering. The obtained functional dependence makes it possible to predict the precipitation of the section with a high degree of probability in the geological conditions of St. Petersburg. It is established that with any combination of the considered parameters, the amount of precipitation of the section of the underwater tunnel with these characteristics does not exceed the values requiring expensive additional fixing of the foundation soils.