## 1 Introduction  
In China, source rock strata are rich in unconventional oil and gas resources. Considerable progress has been made in exploring and developing these resources through targeted theoretical and technological research, a process that is key to increasing reserves and production of these resources [1]. Unconventional oil and gas reservoirs are characterized by low porosity and permeability; therefore, the key to efficient exploitation of these reservoirs is to increase their permeability and improve their seepage conditions, thereby increasing the production per well. In recent years, researchers have proposed a variety of stimulation techniques and methods to improve seepage conditions and to create reservoir fracture networks, such as hydraulic fracturing [2], carbon dioxide fracturing [3], anhydrous liquid nitrogen fracturing [4], the use of acoustic vibration [5], high-temperature thermal stimulation for enhanced permeability [6], and in situ combustion fracturing [7]. Combustion fracturing involves mechanical deformation by shock waves and high-pressure blast products, along with explosion-induced sustained high-temperature thermal effects, which are present around the involved well. These features substantially impact the pore-crack microstructures in reservoirs, thus improving the seepage conditions within. Therefore, assessing the evolution of pore-crack structures in sandstone reservoirs under high-temperature thermal effects and dynamic impacts is essential. Such investigations are of great importance to feasibility studies on the use of combustion fracturing techniques for enhancing reservoir permeability. Extensive research has been conducted on the static and dynamic fracture mechanical behaviors of homogeneous sandstone following high-temperature treatment, achieving notable results [8; 9; 10; 11; 12; 13; 14]. [PERSON] et al. [15; 16] conducted impact compression tests on sandstone specimens subjected to high-temperature cycling and found that the mass, density, and wave velocity of the specimens decreased with a quadratic function of the number of cycles, and the dynamic compressive strength and dynamic strain showed different trends before and after 400 \({}^{\circ}\)C. [PERSON] et al. [17] investigated the dynamic mechanical properties of heat-treated homogeneous coal-bearing sandstone, demonstrating that 500 \({}^{\circ}\)C was the transitional point for the dynamic properties of coal-bearing sandstone. When the temperature exceeded 500 \({}^{\circ}\)C, the dynamic elastic modulus and peak strength of the sandstone dropped sharply, while its dynamic peak strain increased significantly. [PERSON] et al. [18; 19] used a high-speed camera to examine the dynamic failure process of sandstone that had been heat-treated at high temperatures; they found that its dynamic compressive strength initially increased and then decreased as the temperature rose, peaking when the temperature reached 200 \({}^{\circ}\)C. The peak strain increased approximately linearly with increasing temperature. The dynamic elastic modulus showed an overall trend of decreasing nonlinearly; the primary failures of the sandstone were tensile failures. Notably, the higher the temperature, the greater the degree of fracturing and the smaller the fragmented rock mass. The dynamic compressive strength and dynamic elastic modulus of heat-treated homogeneous sandstone show a nonlinear decrease with increasing temperature, and there is a sudden change point around 400-500 \({}^{\circ}\)C. However, natural sandstone reservoirs are usually discontinuous media with various structural planes (such as bedding planes, joint planes, etc.). These bedding planes are usually oriented and have a significant impact on the mechanical properties and failure process of sandstone [20], but there are currently few research reports.