Abstract:
In fractured rock masses, large excavations have an unsupported
stand-up times Jess than the minimum time required to support the roof after the
excavation. Therefore, the principal objective in the design of a support system is to
help the rock mass to support itself. The use of rock bolts is a very flexible
supporting method that can be combined with wire mesh, shotcrete and concrete
lining. During past years a wide variety of dowels and bolt types were developed
but most of them failed within a short period and the cost were high. Advantages of
cable strand supports have been well documented and include flexibility, strength,
and ease of installation. Main objective of this project is to design rock bolts using
discarded wire ropes 01' cables at a low cost. A detailed designing methodology was
carried out to fabricate this bolt. The bolt consists of nearly 1.6m long cable and
16 em of anchored part and cable tightening part. Outer diameter of bolt is 33 mm
and inner diameter is 12 mm and used cable diameter is Smm. Field data illustrated
the amount of load measurements that the bolt can carry is 5 kN, Suggestions were
made to improve the design, which will enhance bolt performance. Field tests
carried out at Bogala Lanka Graphite Ltd proved that cable bolts are effective in Sri
Lankan conditions.
