Numerical analysis of changing the force factors in temporary lining at the tunnel construction by the NATM

Abstract

The paper presents the results of a numerical analysis of force factors in temporary lining at the tunnel construction by New Austrian Tunneling Method (NATM). The relevance of the performed research is substantiated by the complexity of the temporary lining operation in the form of arches combination, anchors, and shotcrete that arose during construction of the Beskydskyi tunnel in Ukraine. NATM, used in construction, is associated with a change in the sectional area of the working and a staged installation of temporary lining, which leads to a gradual change in the stress-strain state of the “temporary lining – surrounding massif” system. In turn, this leads to a change in the force factors (bending moments and normal forces) in temporary lining. In this study, a series of finite-element models simulating the stages of rock excavation and installation of lining elements have been developed and analyzed. The obtained results allowed to determine the cardinal change of force factors in temporary lining, depending on the stage of construction. Changing the force factors at different stages of the tunnel construction by the NATM makes it possible to perform an optimal selection for temporary lining location.