论证了判定采场主关键层的充分条件应为顶板来压强度条件 .推导出组合关键层弹性模量、承受载荷和极限跨距的计算公式 ,完善了组合关键层理论 .分析了单一主关键层、组合关键层断裂失稳类型判断曲线 ,指出已往文献中所出现的差错 ,并提出了正确的断裂岩块失稳类型判断曲线 ,为组合关键层在浅埋煤层顶板控制中的正确应用提供了依据 .揭示了地表厚松散层浅埋煤层组合关键层自身不能形成三铰拱式平衡的机理 The sufficient conditions for determining the key stratum of the stope should be the compressive strength conditions of the roof, and the formulas for calculating the elastic modulus, load and ultimate span of the key stratum are deduced, and the combined critical stratum theory is improved. This paper points out the mistakes in the literature and points out the correct judgment curve of instability type of rock fracture, which is provided for the correct application of combined key rock in roof control of shallow coal seam The basis revealed that the key layer of shallow coal seam with thick loose layer can not form the mechanism of three-leg arch equilibrium