ABSTRACT
Fiber-reinforced shotcrete and concrete significantly enhance the structural integrity and durability of tunnel constructions, incorporating fibers such as steel, polypropylene, or glass to improve tensile strength, crack resistance, and post-cracking behavior. This study investigates the impact of fiber distribution on fracture parameters and performance using finite element simulations of three-point bending tests on notched beams, generating load-crack mouth opening displacement (P-CMOD) curves. The extended finite element method (XFEM) was employed to simulate crack propagation without re-meshing. Various fiber distributions, including normal, exponential, logarithmic, and Fisher distributions (with K values of 1, 5, 10, and 100), were analyzed. Fisher K=1 demonstrated a balanced performance, effectively simulating all load steps with moderate CMOD values (70.6 µm at 50% peak load and 83.7 µm maximum), an 18.6% CMOD rate, 26.2 Nm work done, and 145.6 N/m fracture energy. Higher K values showed enhanced crack resistance and energy absorption but with potential stress localization issues. Normal distribution exhibited poor crack resistance and energy absorption, while exponential and logarithmic distributions indicated significant energy absorption but poor crack control. The study highlights the importance of fiber distribution in optimizing the mechanical properties and overall performance of fiber-reinforced concrete in tunneling applications and provides a first step in direction of analyzing soil-tunnel-interaction.
