Pressure of surrounding rock of deep-buried loess shield tunnel

With the development of shield tunnel engineering, more and more deep-buried loess shield projects have gradually appeared. The calculation of pressure of the surrounding rock is of great significance to the design of linings and safety evaluation during the service period. The aim of this study is to establish a theoretical solution for pressure of the surrounding rock of deep-buried loess shield tunnel. With the consideration of the continuous conditions of the radial deformation at the interface between the linings and the surrounding rock, the analytical solutions for forces and displacements of the linings and surrounding rock are derived based on the Fenner formula. Then, the analytical solution of pressure of the surrounding rock applicable to loess shield tunnel is given by introducing the structural parameters of loess. Considering the generalized shear strain of the surrounding rock after tunnel excavation, a solving method for the structural parameters of surrounding rock of loess tunnel is given. The influences of humidification on the structural parameters of loess and the pressure of surrounding rock are then discussed by introducing the surrounding rock structural parameters of loess. It is found that the generalized shear strain increases radially in the plastic zone and gradually decreases in the elastic zone. It is basically stable outside the twice the radius of the plastic zone. The structural parameters of loess of the surrounding rock can be recognized as evenly distributed in the plastic zone. When the water content of rock increases from 2% to 20%, the expansion of the plastic zone is about 33%, and the increase of the pressure of the surrounding rock is about 10%. The research results are expected to provide ideas for the calculation of pressure of the surrounding rock of deep-buried loess shield tunnels. © 2021, Editorial Office of Chinese Journal of Geotechnical Engineering. All right reserved.