在我国由于地质构造作用的影响，导致煤层中多存在原生结构煤和构造煤分层的现象；而构造煤的存在导致复合煤层突出危险性急剧增加，这严重制约我国煤矿安全生产。根据软硬复合煤体瓦斯的扩散状态，模拟分析了非稳态扩散复合煤体的力学失稳规律；建立了非稳态扩散的吸附瓦斯膨胀能计算模型，探讨了稳态扩散和非稳态扩散对于吸附瓦斯膨胀能的影响，从能量角度分析了吸附瓦斯膨胀能对突出的控制作用，阐释了非稳态扩散复合煤体的突出失稳致灾机制。结果表明：复合煤层中构造煤的存在能够增加其邻近原生结构煤的塑性破坏程度，提高了原生结构煤塑性区内的瓦斯运移速度，进而增加煤与瓦斯突出危险性；非稳态扩散条件下原生结构煤和构造煤的吸附瓦斯膨胀能是稳态扩散条件的0.50～0.57倍和3.36～3.38倍，复合煤层中由于构造煤的存在导致原生结构煤内部裂隙−基质系统间产生巨大的瓦斯浓度差，使得原生结构煤基质内部的吸附瓦斯迅速解吸，增加邻近原生煤中吸附瓦斯膨胀能，进而使得复合煤层的突出危险性显著增加。

In China, due to the influence of geological tectonics, the phenomenon of primary structural coal and tectonic coal stratification exists in many coal seams. The existence of tectonic coal leads to a sharp increase in the risk of composite coal seam outburst, which seriously restricts the safe production of coal mines. According to the gas diffusion state in soft and hard composite coal bodies, the mechanical instability law of composite coal with unsteady diffusion was simulated and analyzed. The calculation model of adsorbed gas expansion energy by unsteady diffusion was established, and the influence of steady and unsteady diffusion on the expansion energy of adsorbed gas was discussed. The control effect of adsorbed gas expansion energy on outburst was analyzed from the perspective of energy, and the disaster-causing mechanism of composite coal outburst instability by unsteady diffusion was elucidated. The results shown that, the existence of tectonic coals in the composite coal seams could increase the plastic damage degree to the adjacent primary structural coals, and improve the gas migration rate within the plastic zone of the primary structural coals, thus increasing the risk of coal and gas outbursts. The expansion energy of adsorbed gas in primary structural coal and tectonic coal under unsteady diffusion condition was 0.50 - 0.57 times and 3.36 - 3.38 times higher than that under steady diffusion conditions, respectively. The presence of tectonic coals in composite coal seams led to a huge gas concentration difference between the fissure and matrix systems within the primary structural coal, which resulted in the rapid desorption of adsorbed gas within the primary structural coal matrix, increasing the expansion energy of adsorbed gas in the adjacent primary coals, and thus significantly increased the outburst risk of composite coal seam.