A fact is revealed that the floor of roadway is subsided under the presure ofthe roadway wall during delivering pressur from the roof.

• 茂名矿区的底胶变形由两帮岩柱传递顶板压力开始，在挤压底板的同时和岩帮一起下沉，底板受严重压缩变形后破裂并臌起。