STUDY ON THE MECHANICAL CHARACTER ISTICS OF COMBINED MOTION OF OVERLYING ROCK STRATUM

The combined key stratum is regarded as a crucial factor for the motion of overlying rock strata. The stress of the combined key stratum is discussed on the basis of elastic thin slab theory and the laminated slab theory of compound material mechanics. The study result provides an approach to calculate the overall strength of the combined key stratum. In the actual engineering practice of mining subsidence controlling, the maximum load for instability of the combined key stratum is calculated by using the structural plastic limit analysis theory and the expression of the plastic limit load of the key stratum was obtained on the condition of sufficient mining. On this basis, a new method for judgment of the key stratum position is also found from another point of view. The result provides a reference for grouting and reducing subsidence.