An experimental study was conducted to investigate the dynamic mechanical behavior, energy dissipation, and fragmentation characteristics of sandstone specimens reinforced with NPR cables under impact loading. Dynamic compression tests were performed on unanchored specimens, PR-anchored specimens, and NPR-anchored specimens using a 50 mm-diameter-split Hopkinson pressure bar (SHPB) at incident gas pressures of 0.26, 0.28, and 0.30 MPa. Dynamic stress response, strain field, and cable force evolution were systematically analyzed, and the failure modes were evaluated on the basis of fractal theory and energy dissipation principles. Experimental results show that NPR-anchored specimens exhibit higher dynamic peak stress, up to 39.02% greater than unanchored specimens and 22.61% greater than PR-anchored specimens, along with lower maximum principal strain, reduced by 36–52%, fewer surface cracks, and higher dynamic peak strain with 12.60–20.40% above PR-anchored specimens. Based on the force–time curve of NPR cables, the constant-resistance platform provides extended strain capacity and gradual stress decline, effectively suppressing lateral deformation and macro-crack propagation. Energy dissipation ratio EA/EI of unanchored specimen is 0.305, and the rock samples are fragmented after impact. While PR-anchored specimens remain rupture (EA/EI = 0.272), and NPR-anchored specimens exhibit part-rupture (EA/EI = 0.251), representing reduction in energy dissipation of 7.4–17.9%, reduced transmitted energy (17.88–19.07% of incident energy), and increased reflected energy (56.10–56.66%). In addition, fragments produced by NPR-anchored specimens tend toward slice-like morphology with broader LTR distribution, nearly unchanged LWR distribution, and stable WTR range. Furthermore, the fractal dimension of unanchored (Dm ∈ [2.08,2.33]) and PR-anchored specimens (Dm ∈ [1.63,2.07]) varies in a wide range, while NPR-anchored specimens remain constant (Dm = 2) across all impact pressures, reflecting reduced fragmentation and improved integrity. These findings highlight the superior impact resistance of NPR cables and provide a quantitative basis for understanding their role in mitigating rock failure under dynamic loading.Highlights<UnorderedList Mark="Bullet"> <ItemContent> An SHPB experiment for investigating the failure modes, dynamic stress response, principal strain field (by 3D-DIC), and cable force evolution of NPR cable-anchored rock specimen under different incident gas pressures. </ItemContent> <ItemContent> Specific values of energy dissipation ratio EA/EI have been defined to represent the fragmented, rupture, and part-rupture state of rock. </ItemContent> <ItemContent> The characteristics of the fractal dimension of unanchored, PR-anchored, and NPR-anchored rock specimens after SHPB tests have been revealed. </ItemContent> </UnorderedList>

Dynamic Mechanical Behavior and Fractal Characteristic of NPR Cable-Anchored Sandstone Specimens in SHPB Tests

期刊论文
发表日期：

2026年2月26日

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Jiong Wang,
Yiwen Chang,
Wenzhao Liang,
Biaowei Sang,
Lei Ma,
Dongqiao Liu,
Siyu Wang,
Manchao He

摘要

An experimental study was conducted to investigate the dynamic mechanical behavior, energy dissipation, and fragmentation characteristics of sandstone specimens reinforced with NPR cables under impact loading. Dynamic compression tests were performed on unanchored specimens, PR-anchored specimens, and NPR-anchored specimens using a 50 mm-diameter-split Hopkinson pressure bar (SHPB) at incident gas pressures of 0.26, 0.28, and 0.30 MPa. Dynamic stress response, strain field, and cable force evolution were systematically analyzed, and the failure modes were evaluated on the basis of fractal theory and energy dissipation principles. Experimental results show that NPR-anchored specimens exhibit higher dynamic peak stress, up to 39.02% greater than unanchored specimens and 22.61% greater than PR-anchored specimens, along with lower maximum principal strain, reduced by 36–52%, fewer surface cracks, and higher dynamic peak strain with 12.60–20.40% above PR-anchored specimens. Based on the force–time curve of NPR cables, the constant-resistance platform provides extended strain capacity and gradual stress decline, effectively suppressing lateral deformation and macro-crack propagation. Energy dissipation ratio E_A/E_I of unanchored specimen is 0.305, and the rock samples are fragmented after impact. While PR-anchored specimens remain rupture (E_A/E_I = 0.272), and NPR-anchored specimens exhibit part-rupture (E_A/E_I = 0.251), representing reduction in energy dissipation of 7.4–17.9%, reduced transmitted energy (17.88–19.07% of incident energy), and increased reflected energy (56.10–56.66%). In addition, fragments produced by NPR-anchored specimens tend toward slice-like morphology with broader LTR distribution, nearly unchanged LWR distribution, and stable WTR range. Furthermore, the fractal dimension of unanchored (D_m ∈ [2.08,2.33]) and PR-anchored specimens (D_m ∈ [1.63,2.07]) varies in a wide range, while NPR-anchored specimens remain constant (D_m = 2) across all impact pressures, reflecting reduced fragmentation and improved integrity. These findings highlight the superior impact resistance of NPR cables and provide a quantitative basis for understanding their role in mitigating rock failure under dynamic loading.

Highlights

An SHPB experiment for investigating the failure modes, dynamic stress response, principal strain field (by 3D-DIC), and cable force evolution of NPR cable-anchored rock specimen under different incident gas pressures.

Specific values of energy dissipation ratio E_A/E_I have been defined to represent the fragmented, rupture, and part-rupture state of rock.

The characteristics of the fractal dimension of unanchored, PR-anchored, and NPR-anchored rock specimens after SHPB tests have been revealed.