Effect of different fiber type on sprayed concrete support capacity

Abstract

Nowadays there are several types of fiber for the reinforcement of the sprayed concrete used in tunnel support; most popular among them are steel fibers and macro synthetic fibers. However, in most cases the assessment of fiber reinforced sprayed concrete ductility is focused on the fulfillment of energy absorption capacity requirements without considering the effect of the reinforcement type on the Load-Displacement behavior. The following study aims to find out if the support capacity provided by each fiber type is the same for similar levels of energy absorption capacity or how it can be affected through the analysis of the load bearing capacity. After the analysis of energy absorption tests according to EFNARC of more than 50 specimens separately reinforced with steel and macro synthetic fibers, it was observed the specimens reinforced with steel fiber absorbed more energy since the beginning of deformation than those reinforced with macro synthetic fibers. In other words, the required work to start deforming the steel fiber reinforced sprayed concrete is greater than the required with the other fiber type. Likewise, the ultimate strength or maximum load bearing capacity provided by steel fibers was higher than the other fiber type. Therefore, the support capacity of the sprayed concrete and the related safety factor provided by each fiber type is different