Tunnel lining roof bolt anchorage strap - has domed portions at clearance holes forming overlap zones for strap ends

摘要

The anchorage system for tunnel lining uses overlapping straps (a, b, c) which are held in tension against the upper curved surface by radial roof bolts (e), and securd by nuts and washers. These straps are designed to give support over a large surface area. Each strap has a raisd domed part each end, where the bolt passes through, and the ends of the straps overlap in this region. The clearance hole for the bolt is elongated. The domed part may be elongated also, or alternatively may be open ended.