NPR (Negative Poisson's Ratio Bolt) is a constant-resistance, large-deformation support material developed. It is specifically designed to address geological hazards such as deep high ground stress, rockburst, and large deformation in soft rock.

Core Definition and Principle
Name Meaning: NPR stands for "Negative Poisson's Ratio," referring to the unique mechanical effect of a material expanding laterally under tension and contracting laterally under compression.
Working Mechanism: Ideal elastoplastic constitutive relations are achieved through macroscopic NPR structures (such as the sliding friction between a cone and a casing) or microscopic NPR steel. After reaching the critical resistance, the anchor can undergo meter-level large deformation while maintaining constant high resistance, avoiding the sudden fracture caused by "neckback" in traditional anchors.
Key Characteristics: High constant resistance (resistance does not fluctuate with displacement), large deformation (elongation can reach 20%-68%, while ordinary steel is only about 5%), superior energy absorption, and resistance to dynamic shear.

Main Advantages:
Solving the "Strength-Toughness Contradiction": Traditional high-strength steel often has poor ductility. NPR materials simultaneously achieve high strength (yield strength can reach over 1000MPa) and high toughness; a 1-meter length of material can be stretched to over 1.6 meters without breaking.
Adapting to Large Deformation Disasters: Under dynamic loads such as tunnel compression and fault slippage, it can continuously absorb energy and maintain support effectiveness, with a significantly longer service life and greater contribution value than ordinary anchor bolts.
Non-magnetic and Uniform: Some NPR steels have a fully austenitic structure, exhibiting non-magnetic properties and uniform deformation without localized weaknesses.

Time：01/07/2026 16:38:12

NPR rock bolt steel is a new type of reinforcing steel material, also known as negative Poisson's ratio. It possesses exceptional mechanical properties such as high constant resistance, large deformation, energy absorption, and impact and explosion resistance. Under tension, the material expands laterally within its elastic range; conversely, under compression, it contracts laterally. Traditional PR materials will break after reaching their ultimate load, while NPR structures can undergo large deformations without breaking after reaching a constant resistance value. Compared to PSB and HRB reinforcing bars, NPR rock bolt steel, due to its non-magnetic, high-strength, high-toughness, and highly uniform elongation characteristics, and its ability to adapt to large deformations, has broad application prospects in energy mines, transportation tunnels, earthquake-resistant buildings, and bridge engineering.

Time：26/06/2026 16:39:59

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