The hard and stiff strata (key strata) bear the overburden load in the form of a voussoir beam structure (VBS) after break. The VBS affects both the surface subsidence and the stope underground pressure. Therefore. the reasonable method to predict the surface subsidence is based on the whole subsidence formulae of the VBS. https://www.pomyslnaszycie.com/white-and-green-bulletin-board-border-simply-boho-schoolgirl-style-on-sale/