Spalling strength and failure modes of hole sandstone under dynamic loading: Effect of filling material strength and filling radius

Abstract

Natural discontinuities, such as holes and cracks in rock masses, often act as stress concentration zones, rendering them highly susceptible to spalling failure under dynamic loading conditions, a critical threat to the safety and stability of underground structures. Filling reinforcement is an effective means to control this kind of damage. Therefore, in this paper, the effects of filling material strength and filling radius on the dynamic mechanical response and spallation failure characteristics of porous sandstone are systematically studied using a φ 50 mm split Hopkinson pressure bar (SHPB) system and PFC2D numerical simulation method. The results demonstrate that increasing both the strength and radius of the filling material significantly enhances spalling resistance, delays crack initiation, and reduces the number of spalling cracks, underscoring its capacity to buffer stress waves and modulate fracture development. High-speed imaging directly captures the delayed initiation and propagation of cracks within the filling material. The numerical simulation results further reveal that the filling position is another key factor affecting the reinforcement effect. Fillings at the transmission end experience greater stress superposition, resulting in more severe spalling damage compared to those at the incident end. These insights offer practical guidance for optimizing filling strategies in practical engineering applications.

Keywords

holed sandstone / filling material / spalling / stress wave propagation / PFC2D numerical modeling

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