# Energy Evolution and Fine Structure Effects in Typical Rocks Subjected to Impact Loading

## TL;DR

This study explores how different types of rocks behave under impact loading, revealing insights into their mechanical properties and energy evolution for applications in mining and rock stability.

## Contribution

The study introduces an energy-time density index and a dynamic strength–energy-time density mapping model to better understand rock failure mechanisms under impact.

## Key findings

- Basalt, blue sandstone, and granite show brittle failure, while red and green sandstone exhibit ductility.
- Green sandstone has the highest energy-time density, followed by red sandstone, granite, blue sandstone, and basalt.
- Fractal analysis shows higher fractal dimensions correlate with complex microcrack structures and energy dissipation.

## Abstract

To investigate the mechanical behavior and energy evolution characteristics of various rock materials under impact loading, dynamic impact tests were conducted on five representative rock types using a split Hopkinson pressure bar (SHPB) apparatus, combined with X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The dynamic mechanical response, energy characteristics, mineral composition, and associated microstructural features of these typical rocks were systematically analyzed. The results show that basalt exhibits the highest peak strength, followed by blue sandstone and granite; all three display typical brittle failure characteristics, whereas red sandstone and green sandstone demonstrate greater ductility and plastic deformation capacity. By introducing the energy-time density index, the energy-time density of the rocks ranks from strongest to weakest as follows: green sandstone, red sandstone, granite, blue sandstone, and basalt. An innovative dynamic strength–energy-time density mapping model was established to elucidate the clustering and distinguishing characteristics of these rock materials. Assay results and mesoscopic images confirm the relationship between mineral composition and the fine structure of rock fragmentation mechanisms, highlighting that the critical transition from intergranular to transgranular fracture is the key mechanism governing impact pulverization. Furthermore, fractal analysis reveals that higher fractal dimensions are associated with more complex microcrack structures and may correlate with the corresponding energy dissipation intensity. These findings provide profound insight into the failure mechanisms of rocks under dynamic loading, offering significant theoretical value and engineering application prospects, particularly in fields such as mining excavation and rock mass stability assessment.