Three-dimensional mesoscale numerical study on the mechanical behaviors of SFRC tunnel lining segments

Abstract

This study investigated the mechanical properties and failure patterns of the steel fiber reinforced concrete (SFRC) lining segments with different fiber parameters using a three-dimensional mesoscale model. The research highlights a sophisticated mesoscale model of the SFRC tunnel segment with randomly distributed steel fibers and considers the nonlinear mechanical behaviors of steel fiber, concrete and the bond-slip effect. The entire paper is organized as follows: firstly, a generation algorithm to achieve the discrete distribution of steel fibers and the nonlinear constitutive models of steel fiber and concrete were introduced. The bond-slip effect between steel fiber and concrete was converted equivalently. Secondly, the numerical model was further validated by conducting a series of simulations, including the single steel fiber pullout, uniaxial compression, splitting tension and flexural testing. Finally, the mesoscale model was employed to investigate the influences of steel fiber parameters on the mechanical properties and failure patterns of SFRC tunnel segments. It revealed that the typical features of the cracked SFRC segments in the numerical simulation are highly consistent with the experimental results. The randomly distributed steel fibers can well bear and transfer the tensile stress, which effectively improves the crack resistance of the tunnel segment. The load-bearing capacity of SFRC segments linearly increases with the steel fiber content and length while maintains a negative relationship with the steel fiber diameter. Moreover, the addition of steel fiber improves the toughness of the segment more significantly than the maximum load. The proposed model provides an applicable method for further analysis, design and optimization of SFRC segments in real tunneling engineering.