| 摘要 |
Coal is mined using water jets to a remove a layer of thin horizontal slices of coal. The thickness of the layer is sufficiently small that elastic deformation of the roof of the layer due to settling will cause the roof to rest against the floor of the layer. A number of additional layers of slices are then extracted in the same manner, each immediately below the floor of the preceding layer. The thickness and location of these layers wiht respect to previous layers is such that elastic deformation of the roof of the first layer due to settling will cause the roof to rest against the floor of the last layer of slices. Through the sequential mining of layers in this manner from top to bottom, the entire seam of coal is extracted and the mine roof rests upon the mine floor without the need for artificial roof support.
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