| 摘要 |
The lining sustains the roofs of mining galleries and comprises a frame of rolled steel sections (1, 2) having a vee-shaped profile. These are fitted together to give a semicircular form, the ends of one section overlapping the adjacent section. The joint is clamped by two straps (4a, 4b) one positioned each side of the joint. These straps are U-shaped, their ends turned outwards parallel to form flanges (4c, 4d). Holes through these accept bolts (6), the lower hole having a hemispherical internal profile (4c). The tightening nuts (8) also have a hemispherical mating surface (8d), or a standard nut and a hemispherical collar washer can be used. |
