Analysis of the Influence of Upper Protective Layer Mining on the Effect of Pressure Relief and Protection of Coal and Rock Masses between the Lower Overburden Layers

Figure 3

Simplified additional stress distribution graph before and behind the working face. P—vertical initial stress of rock, γH; d₁—length from peak advanced abutment pressure to the abutment pressure falling within the initial stress zone of rock; d₂—length from coal wall of the working face to the peak abutment pressure; d₃—length of goaf with zero initial stress of rock; d₄—length from residual abutment pressure in the goaf until the initial stress of rock is recovered; and H—interbed spacing.