Experimental study and numerical simulation of the effect of different fiber types on the basic mechanical properties of shotcrete

Abstract

The enhancement effects and mechanisms of different types of fibers on the basic mechanical properties of concrete were analyzed, aiming to guide the selection of suitable fiber types and dosages for grouting projects. This study selected steel fibers, glass fibers, and polypropylene fibers as research subjects. Through laboratory tests, numerical simulations, and field experiments, it investigated the enhancement laws of flexural and compressive strengths of concrete with different dosages of these three fibers. The study shows that: (1) After 28 days of curing, the flexural strength of concrete with steel fibers, glass fibers, and polypropylene fibers peaked at dosages of 2.0%, 1.5%, and 2.0%, respectively. Compared to plain concrete, the increases were 118.6%, 42.86%, and 138.6%, respectively. The compressive strength of concrete increased the most with dosages of 0.5%, 1.0%, and 2.0% for steel fibers, glass fibers, and polypropylene fibers, respectively, with increases of 2.13%, 10%, and 18.3%. It can be seen that the impact of these three fiber types on the compressive strength of concrete is significantly less than their impact on flexural strength. For enhancing flexural strength, the order is polypropylene fibers > steel fibers > glass fibers. Conversely, for compressive strength, the order is polypropylene fibers > glass fibers > steel fibers. (2) Based on ABAQUS numerical simulations, microscopic analysis indicates that fibers, due to their high yield capacity, enhance the connections between concrete elements, reduce stress concentration, and improve the mechanical properties of concrete. (3) For shotcrete, due to its high flexural strength requirements and the tendency of steel and glass fibers to agglomerate, polypropylene fibers at a dosage of 2.0% were preferred. (4) Using the optimal dosage, it was successfully applied to the wet shotcrete support of a return air shaft in a mine, where the maximum deformation of the roof and sides of the tunnel remained within allowable limits, meeting the normal usage requirements of the tunnel. The research findings can offer guidance and reference for the selection and further application of shotcrete.