Effects of fiber and rubber materials on the dynamic mechanical behaviors and damage evolution of shotcrete under cyclic impact load

Abstract

Dynamic loads in underground construction environments can significantly damage supporting structures. The mechanical behavior of shotcrete under high strain rate impact has received significant attention. However, few researchers have investigated the performance degradation law, damage evolution process, and failure mode of shotcrete under cyclic impact load. This study utilized the split Hopkinson pressure bar (SHPB) to conduct cyclic impact loading experiments on shotcrete reinforced with copper-plated steel fiber (CSF), basalt fiber (BF), polypropylene fiber (PF), and rubber particles (RP). The addition of reinforcing materials significantly improved the dynamic mechanical properties of shotcrete. Under cyclic impact, the stress-strain curves of reinforced shotcrete basically coincided in the elastic deformation stage. As the content of the reinforcing materials increased, the dynamic mechanical properties of the shotcrete improved. The performance of fiber-reinforced shotcrete improved under the compaction effect caused by the first impact. Only rubber shotcrete sustained 6 impacts under cyclic constant impact pressure. Based on the ultrasonic velocity obtained by non-destructive testing, a cumulative damage evolution model during cyclic impact was established. The incorporation of RP effectively slowed down the damage evolution rate and increased the shotcrete's bearing capacity for cumulative damage. This paper conducted a comprehensive comparative analysis and concluded that the addition of rubber particles at a content level of 5% was the most cost-effective option to enhance the dynamic mechanical properties of shotcrete. The findings provide a theoretical reference for underground engineering supporting structures subject to long-term cyclic dynamic loading.