## 1 Introduction  
With the continuous development of underground engineering construction, the development of China's underground resources is gradually deepening. Compared to shallow projects, deep underground projects are facing geological hazards, and engineering risks are more complex and variable [1], especially in the use of \"drilling and blasting\" construction, where the instantaneous strong impact load will bring about a more unpredictable risk of underground engineering. Due to the limitations of shallow rock mechanics, the existing relevant theories cannot be applied well to deep engineering [2]; based on this problem, scholars have carried out a lot of research. In the construction of underground engineering, the surrounding rock is affected by construction disturbance and geological tectonic movement, resulting in there being different degrees of internal damage. Regarding the mechanical properties of damaged rock, [PERSON] et al. [3] conducted dynamic mechanical tests on granite with prefabricated parallel fissures and investigated the effects of prefabricated fissure angles and impact rates on energy dissipation and damage in granite. [PERSON] et al. [4] prefabricated sandstones with different fissure angles, combined with digital image technology to carry out an impact test, revealing that increasing impact rates and crack angles enhanced the dynamic strength of sandstone and made crack propagation more complex. [PERSON] et al. [5] used a split Hopkinson bar device to obtain dynamic mechanical properties, fracture characteristics, and energy evolution laws for sandstones with multiple parallel fissures. The results of [PERSON] et al. [6] and [PERSON] et al. [7] showed that the original cracks in the rock affect the dynamic properties and crack extension of the rock. [PERSON] et al. [8] used a crack propagation instrument to record the crack propagation parameters of the single-cleavage triangular sandstone sample under impact and calculated the dynamic stress intensity factor of the rock samples. Additionally, in deep environments, the influence of high crustal stress on the surrounding rock is not to be underestimated. Experiments using Hopkinson devices capable of applying a confining pressure are a common method of investigating such problems. In this regard, [PERSON] et al. [9] investigated the damage pattern of rocks using a split Hopkinson bar to which a confining pressure can be applied. [PERSON] et al. [10] investigated the dynamic mechanical properties and energy dissipation law of fissured sandstones under different confining pressures. [PERSON] et al. [11] used cylinders of three different materials to achieve the pressurization of the rock and investigated the dynamic properties and damage modes of the rock. The above literature has carried out extensive studies on the dynamics of damaged rocks. But rock is a non-homogeneous natural material, and the development of internal pore fracture after perturbation is highly uncertain, and artificially prefabricated fissures do not reflect well the internal conditions of damaged rocks in actual engineering. The change in the macroscopic mechanical properties of rock mass is caused by the change in the meso-mechanical properties and microscopic pore structure. To better study the microscopic changes in rocks, CT scanning technology has been introduced into the study of rock mass mechanics and has been widely used. [PERSON] et al. [12] analyzed the mineral composition of rock based on CT scan images and determined the spatial distribution of each component in the rock sample based on three-dimensional reconstruction. [PERSON] et al. [13] carried out uniaxial compression tests and CT scans on jointed granite, studying the extension of internal joints. [PERSON] et al. [14] reconstructed three-dimensional visualization fractures based on CT images and analyzed the relationship between the damage degree and the fractal dimension.