| 摘要 |
An improved device for anchoring mine roofs utilizing bolts prestressed to place them under high tension loading is disclosed. The bolt is secured by an anchor consisting of an expandable shell and an expander nut with the nut being movable lengthwise of the hole by turning the bolt. The surfaces of the anchor which engage the surfaces of the hole in which it is installed are coated with sand bonded thereto by a thin coat of a suitable adhesive. By the use of a polywax material to lubricate the threading of the bolt and the camming surfaces of the expander nut, very high lateral expansion forces are generated to press the sand coated surfaces of the anchor against the rock walls creating a high tension load supporting engagement between the anchor and the rock matrix.
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