| 摘要 |
<p>A tunnel support arch formed from I-section or channel section material and divided into a crown portion (2, 52) and leg portions (4, 54) and in which holes (10, 58) are provided through the two flanges (6, 8) of both the crown and upper ends of the legs; across the junction between the legs and the crown, splicing plates (12, 14, 16, 18, 30, 60) are arranged to be bolted to both flanges of both the crown and leg portions; preferably at least one splice plate (12, 18,30) has at least one pair of bolt holes (32) spaced apart in the elongate direction (L) with a slot or groove (35) providing an area of reduced strength extending from each bolt hole towards the nearest elongate end (38) of the plate. The invention prevents sudden fracture of the joint between crown and legs and in the case of bolt holes in the splice plates where an area of reduced strength extends from each bolt hole additional warning is given of joint failure.</p> |
