## 5 Conclusions  
This study utilized CT scanning combined with three-dimensional reconstruction technology and multifractal theory to examine the impact of in situ stress on the blasting damage characteristics of rock, and employed SEM electron microscopy and fracture morphology analysis to investigate the influence of in situ stress on rock fracture patterns during blasting. The main conclusions are as follows:  
(1) From the macroscopic and mesoscopic perspective, in situ stress has a significant impact on the blasting damage characteristics of rock. Experimental research indicates that, under in situ stress, the rock's ability to resist the effects of blasting stress waves and blasting gas is enhanced. With the increase in the in situ stress, the overall damage level of the sandstone specimens gradually decreases. As the in situ stress increases from 0 MPa to 3 MPa, the relative damage \(\Delta\alpha\) value in the bottom segment (at \(h=20\) mm) decreases from 0.3546 to 0.2323; in the charge segment (at \(h=60\) mm), it decreases from 0.3736 to 0.2622; in the stemming segment (at \(h=100\) mm), it decreases from 0.3956 to 0.2806.  
(2) From both the macroscopic and microscopic perspectives, the damage characteristics of the different rock segments vary. The experiment uses hole-bottom blasting, with a shorter stemming segment. Due to the reflection of blasting stress waves and boundary effects, in the same sandstone specimen, the damage level of the stemming segment is highest, followed by the charge segment, with the bottom segment exhibiting the lowest damage level. Under an in situ stress of 0 MPa, the relative damage \(\Delta\alpha\) value decreases from 0.3956 at \(h=100\) mm (the stemming segment) to 0.3736 at \(h=60\) mm (the charge segment), and finally to 0.3516 at \(h=10\) mm (the bottom segment). As the in situ stress increases, the damage levels in all three segments gradually decrease, with the cracks in the bottom segment disappearing first, thus maintaining better integrity. Under an in situ stress of 3 MPa, the relative damage \(\Delta\alpha\) value decreases from 0.2806 at \(h=100\) mm (the stemming segment) to 0.2622 at \(h=60\) mm (the charge segment), and finally to 0.2235 at \(h=10\) mm (the bottom segment).  
(3) From the microscopic perspective, in situ stress significantly influences the fracture patterns of rock during blasting. Under blasting loading, the microscopic fracture morphology of the rock mainly exhibits tensile fractures, brittle cleavage fractures, and transgranular fractures. Increasing the in situ stress reduces the blasting energy acting on rock fragmentation, lowering the peak blasting stress and strain rate, and leading to an increase in shear fractures. The blasting fracture surfaces become progressively rougher, and the microscopic fractures in the sandstone gradually transition from brittle cleavage fractures to brittle-plastic quasi-cleavage fractures. In some of the regions, the energy is insufficient to penetrate the grain boundaries, resulting in a transition from transgranular fractures to coupled fractures and intergranular fractures.  
Not applicable.  
The data are not publicly available due to privacy restrictions.  
Author [PERSON] was employed by the company Panzhihua Iron and Steel Group Mining Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.