Rock breaking using liquid nitrogen and water jet: a case of granite

Water jet impact technology has more advantages in environmental protection, safety and quality. This paper innovatively puts forward the new technology of temperature–hydrodynamic coupling effect rock breaking, which can fully utilize the water jet energy and effectively improve the mining and excavation capacity of granite, especially suitable for high-temperature rocks. Taking the common granite in the actual project as an example, the mechanical test and water jet impact test are carried out to study and analyze the temperature–water jet coupling effect. Rock-breaking technology, acoustic emission technology, image recognition technology and nuclear magnetic resonance technology are used to analyze the mechanism of the temperature–water jet coupling effect, supplemented with numerical simulation to verify and analyze. The test results show that: under the action of temperature–hydrodynamic coupling, the granite crushing is more obvious, the degree of influence of liquid nitrogen impact time 120 s > 180 s > 240 s > 300 s > 60 s, and the crushing efficiency is improved by 117%; through numerical simulation to analyze the comprehensive damage factors, the temperature–hydrodynamic coupling effect produces a large number of minor damages in the internal granite; analyzing the stress characteristics of granite. Under the effect of temperature–hydrodynamic coupling, granite is mainly subjected to tensile damage, thus generating cracks to promote granite crushing. The results of the study provide theoretical guidance for practical engineering.