Study on microscopic damage mechanism of marble under blasting action based on XRD crystallographic analysis

In order to study the microscopic damage characteristics of marble by explosive impact loading, we carried out the blasting test of marble with different charges, analyzed the microcrystalline structure of marble specimens before and after blasting by X-ray diffraction and image processing techniques, predicted the location of crack initiation and direction of expansion according to the difference of mineral components, counted the parameters of microcrystalline structure, and explored the mechanism of microscopic impact of explosive impact loading on the structure of marble. The results show that: the diffraction peaks of calcite and quartz minerals in the mineral composition of marble have a high degree of overlap with those of marble, and the effect of magnesite on the diffraction peaks of marble is the smallest; the increase of the explosive impact load destroys the crystal distribution of marble minerals, and the lattice spacing slightly decreases, and the microcrystalline structure becomes more compact. The intensity of the diffraction peaks before the impact is larger, and the difference in the intensity of the diffraction peaks is obvious; after the impact, the other stronger diffraction peaks are more uniform, and the difference between them and the strongest peaks is gradually shrinking; the physical damage caused by blasting impact and the localized weakening area formed by selective particle migration are called the priority locations for the initiation of blasting cracks. For marble, which is more prone to tensile failure in areas with relatively high content of periclase, the stress concentration generated leads to the appearance of small cracks and holes, affecting the initiation and propagation direction of blasting cracks.The diffraction angle in the microcrystalline structure has a relatively stable limiting threshold, and when the size of the diffraction angle is close to this threshold, the effect of the blast impact load on the diffraction angle gradually decreases, and the impact load has the greatest effect on the half-peak width of the calcite in the marble. The research results will provide theoretical basis for the rock damage destruction under blasting action and the stability assessment of blasting engineering.