Failure mechanism of deformed concrete tunnels under plastic ground pressure

Abstract

This paper presents different failure modes as well as the key variables controlling the load-carrying capacity and deformation behavior of concrete tunnels under plastic ground pressure. Based on total strain and the concept of fracture energy, a parabolic compressive softening model as well as a linear tensile softening model is introduced. It is found that the variables, such as the concrete compressive strength, concrete compressive fracture energy, soil stiffness, modes of external loads and inverts, have a great influence on structural performances of concrete tunnels. The final failure of tunnels with inverts is in the mode of compressive crushing under soil stiffness of 110 N/mm, while the final failure of that without inverts is in the mode of cracking failure. Moreover, concrete compressive strength has significant influence on the structural load-carrying capacity, while concrete compressive fracture energy affects remarkably the ductility of tunnel structures.