Abstract: The paper describes the mechanism of protecting the surface buildings by filling the blind mined-out area, deduces the necessary conditions for the surface building not to be destructed and gives out the formulas for the blind mined-out areas of tectonic stress and self-gravity stress destruction types at full extraction and non-full extraction conditions, which can be used in guiding the design for safe and economic protection of surface buildings.

Key words: Surface structure, Blind mined-out area, Filling rate, Full extraction