Study on static and dynamic mechanical properties of polyvinyl alcohol fiber EPP concrete as buffer layer of high geo-stress soft rock tunnel

Abstract

The study is based on the combined advantages of PVA fibers and EPP materials, a new PVA fiber EPP concrete was prepared as a filler material for tunnel buffer layers. 10 groups of specimens with different working conditions were designed and prepared. The failure pattern, physical and mechanical parameters and energy absorption index of the material were analyzed by static mechanical test and Hopkinson pressure bar (SHPB) dynamic compression test. The results indicate that E0 specimen showed brittle failure in static tests and SHPB tests. When PVA fiber and EPP beads were added to the specimen, the failure mode of the specimen changed from brittle failure to ductile failure, and the specimen shows typical core-remaining failure under impact load. The static test results reveal that EPP volume content significantly influences the axial compressive strength, elastic modulus, and confined compressive strength of PVA fiber EPP concrete, while fiber content has the most pronounced impact on splitting tensile strength, Poisson ratio, and dynamic compressive strength. the confined uniaxial compression ontological relationship of PVA fiber EPP concrete under confined compression was established by confined uniaxial compression test, and the formula fitting was carried out. The fitting results were in good agreement with the test data. Based on the stress–strain curve of confined compression, the static energy absorption performance of PVA fiber EPP concrete was discussed. The results show that the energy absorption effect of E60-P18-1.2 concrete is the best; The results of SHPB test showed that comparing the energy absorption value and dissipation rate of each group of specimens under 0.06 MPa air pressure, it was found that the concrete of E50-P12-0.7 had the best energy absorption effect under dynamic compression. These studies provide a valuable theoretical basis for optimizing the design of tunnel buffer layers.