本文以梁的模型探讨了采场上覆老顶岩层岩块结构的失稳过程和失稳条件。通过理论分析和相似模拟试验,得出了岩块间水平挤压力的变化规律,即T～θ曲线在两岩块θ角相等时T值达到最大。提出了岩块回转塑性临界角的概念,从而使得老顶岩块的变形失稳有了初步的定量分析,而且还讨论了滑落失稳和岩块形状的关系。 In this paper, the instability process and the instability of the rock structure overlying the overburden stope are discussed with the beam model. Through theoretical analysis and similar simulation tests, the variation rule of horizontal squeezing force between rock masses is obtained. That is to say, the T - θ curve reaches the maximum when the θ angles of two rock blocks are equal. The concept of the plastic critical angle of rock rotation is put forward, so that the deformation and instability of the old rock block are preliminary quantitatively analyzed. The relationship between the rockfalling instability and the rock shape is also discussed.