Visualization and quantitative characterization methods of post-blast rock fracture structure

Abstract

The quantitative characterization of post-blast rock damage has been a key problem in the field of engineering blasting, and the process of post-blast rock crack initiation, expansion and evolution until penetration is the main cause of rock rupture. In order to study the evolution process of crack expansion and fracture mode within the blasted rock, the industrial CT was used to scan and observe the rock after the blast, a three-dimensional rock fissure model was constructed through image stack vectorization, and statistically the characteristic parameters of the crack structure were analyzed to quantitatively characterize the degree of rock damage and crack expansion. Combined with numerical simulation to analyze the attenuation law of the explosion shock wave pressure, the SEM scanning test was used to study the micro-morphological characteristics of the rock at different locations during the blasting process, and to compare the correlation mechanism between the change of fracture elemental composition and the fracture mode. The results of the study show that using the equivalent sphere method to statistically analyze the fracture structure at different scales within the rock body, the number of microfractures is large and uniformly distributed, and the main fracture is large in volume and has good connectivity. With the increase of the diameter of the fracture equivalent sphere, the fracture surface area and volume exhibit an increase trend. The fracture rate in the three-dimensional reconstruction of the fracture structure can characterize the local crack expansion characteristics of the rock, the fracture rate and three-dimensional fractal dimension of the near zone of the explosion is much larger than that in the far zone of the explosion, indicating that the fracture expansion in the fracture process of the rock evolution is carried out in this stage. Compared with the far zone of the explosion, the peak pressure is high and slow decay rate, making the entire blasting process of the rock microscopic fracture pattern changes, roughly presenting the direction from the fracture along the crystalline fracture to the fracture through the crystalline fracture, brittle fracture to the direction of plastic damage. The changes in non-metallic elements have a significant impact on the transition of each stage of the fracture pattern, the fracture pattern transition region of the non-metallic elements occurring in an obvious decrease in the content. With the weakening of the blasting effect, the rock rupture gradually tends to be disordered and disorganized, and the fracture is not limited to the deconvoluted surface and grain boundaries during rupture.

Keywords

• blast mechanism
• industrial ct scanning
• three-dimensional reconstruction
• fractal dimension
• scanning electron microscopy
• energy spectroscopy