## 1 Introduction  
Coal and gas outbursts are common gas hazards in underground coal mining and have garnered significant attention worldwide [1, 2]. Since the first recorded outburst at the Issac coal mine in France in March 1834, over 30,000 outbursts have been reported globally [3, 4]. The outburst process involves the violent ejection of broken coal and rock mixed with high-pressure gas [5, 6, 7, 8]. This generates a high-velocity stream of pulverized coal and gas that can damage shaft facilities, disrupt the ventilation system, and potentially trigger secondary hazards such as gas explosions, asphyxiation, and combustion, ultimately resulting in severe economic losses and human casualties [9, 10, 11, 12]. Coal and gas outbursts are particularly prevalent in high-gas outburst coal seam groups. To prevent such accidents, efficient gas extraction through pressure relief from the multiple protected seams of these high-gas outburst coal seam groups is essential [13, 14, 15]. The key to this process lies in understanding the seepage behavior of coal rock bodies in the three zones of the overburden in multi-protection mining. Therefore, experimental research on the seepage law of coal rock bodies in these three overburden zones is critical for preventing coal and gas outburst accidents in the multi-protection mining of high-gas outburst coal seam groups. After mining the protective layer of the coal seam group, the overlying rock layers are divided into the caving zone, fracture zone, and curve subsidence zone, collectively referred to as the three zones of overburden [16; 17; 18], and the distribution characteristics of the three zones of the overlying rock layers are shown in Figure 1. The caving zone consists of broken coal and rock bodies. As the working face advances, the overlying rock layer sinks and compacts the mining airspace, gradually restoring stress in the mining airspace. As a result, parameters such as porosity and permeability continuously change [19; 20]. It has been observed that the permeability of broken coal seams decreases significantly after each cycle, with a greater impact during the loading stage. The highest irreversible permeability loss occurs at a coal-to-rock ratio of 50% [21; 22]. In a study of the stress-permeability relationship of broken coal, rock, and coal-rock combinations in a caving zone, it was found that permeability stress sensitivity and loss are significantly higher in the first loading-unloading cycle. Re-crushing and re-arrangement were identified as key factors contributing to porosity reduction and permeability decrease [23; 24]. The compaction and permeability evolution of broken coal masses in the goaf were also analyzed. This study showed that, under isotropic loading, smaller particle sizes led to greater crushing in mixed particle samples. Additionally, the stress sensitivity of permeability decreased with increasing elastic modulus, effective stress, and Poisson's ratio [25]. Furthermore, the permeability characteristics of broken coal masses under cyclic loading and unloading conditions revealed that permeability is primarily determined by porosity and follows the cubic law. Stress sensitivity and permeability loss were observed to decrease as the number of loading cycles increased [26]. The fractured zone above the caving regions exhibits complex permeability characteristics influenced by the evolution of structural damage. Quantitative studies show that fracture network geometry significantly affects gas migration efficiency, with fractal dimension values (D = 1.62-1.78) strongly correlating (R\({}^{2}\) = 0.86) with permeability enhancement rates [27; 28]. Stress-path dependency has been identified as a key control factor, where mining-induced stress redistribution can alter fracture aperture by 0.15-0.38 mm, resulting in 3-8 times variations in permeability across different zones [29; 30]. Multi-physics coupling mechanisms further complicate permeability evolution.