Influence of vibration loading on impact crack propagation and energy utilization efficiency in green sandstone
[Objective]In rock-crushing processes,external loading methods are important factors affecting the mechanical properties and fracture behavior of rocks.Among these loading methods,vibration and impact methods are the most common ones.However,previous research has mainly focused on macroscopic failure features and energy dissipation properties under the singular loading of vibration or impact.Research on the composite loading of vibration and impact is relatively scarce,and few studies have investigated the influence of vibration loading on the microscopic fracture characteristics and energy evolution during rock impacts.In particular,quantitative characterization studies are lacking.The research on the influence of vibration loading on the propagation of impact cracks and the energy utilization efficiency in rocks has significant academic and engineering applications to fully adapt to the needs of modern mine construction and high efficiency,energy saving,and green production.[Methods]The quasi-brittle green sandstone material,commonly used in rock-crushing operations,was taken as the research object.The macro/micromechanical response relationship of green sandstone was established by integrating indoor experiments with microscopic parameter calibration.The parallel bonding model was adopted,and two loading methods-impact and composite loading of vibration and impact-were compared and analyzed to investigate the influence of vibration loading on the propagation of impact cracks and the energy utilization efficiency in the failure process of green sandstone.The analysis was conducted using the particle flow code(PFC).[Results]The research results indicate that under the same impact velocity,increasing the frequency or amplitude of vibration leads to an increasing trend in the number of cracks in green sandstone.Under the two loading methods,the maximum number of cracks in green sandstone shows a nearly linear increase as the impact velocity increases,with the majority being tensile cracks.The distribution characteristics of cracks exhibit the X-shaped conjugate slope.However,the growth rate of cracks is relatively high under composite loading of vibration and impact.The quantitative characterization of the increase in the number of cracks and impact velocity under vibration loading is established.Under equivalent impact velocity,as the frequency and amplitude increase,there is a corresponding increase in both the proportion of vibration input energy and the energy utilization efficiency in green sandstone.However,as the impact velocity increases,the proportion of vibration input energy within the total input energy in green sandstone decreases.Concurrently,the maximum energy utilization efficiency shows a trend of rapid increase followed by a decrease,with the maximum increase reaching 0.725％.[Conclusions]In practical rock-crushing applications,appropriately increasing vibration loading can exacerbate the damage and deterioration of rocks.This process significantly enhances the energy utilization efficiency with lower energy input.This study preliminarily explores the impact of vibration loading on the propagation of impact cracks and the energy utilization efficiency in green sandstone to provide a reference for the rational selection of parameters in rock-crushing processes.
green sandstonevibration loadingcrack propagationfracture energy
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