Dynamic fracture evolution and energy dissipation mechanisms in geothermally exposed shotcrete under high-velocity impact

Abstract

To investigate the dynamic mechanical properties of underground shotcrete under high-temperature conditions, dynamic compression experiments were conducted using a φ50 mm split Hopkinson pressure bar (SHPB) system integrated with a heating apparatus. A high-speed camera captured the impact-induced dynamic fracture evolution, enabling detailed analysis of specimens with varying damage severities. Results demonstrate that the dynamic compressive strength of shotcrete exhibits a positive correlation with strain rate but decreases with rising temperature. Four distinct failure modes were identified: intact, crack propagation, block separation, and structural disintegration. Each distinct failure mode observed experimentally corresponds to a specific stress–strain curve. The failure process corresponds to a specific point on the stress–strain curve. The study further examined stress–strain response characteristics and energy dissipation mechanisms during failure. Two predictive models were developed: one establishing the relationship between energy dissipation rate and dynamic compressive strength, and another correlating temperature with particle fineness modulus. The dynamic performance test results of shotcrete were used to independently validate the two models. These models advance the understanding of shotcrete behavior under coupled thermo-mechanical degradation, providing a theoretical framework for analyzing energy transfer and stress evolution during impact events.