Numerical Analysis on the Performance Evaluation of Cablebolts as Tunnel Supports

Cablebolts used to be employed as auxiliary supports where long or high capacity bolts are needed, but become competitive by the improvements in supportability and easiness in handling. Based on the test results obtained from various researches, the performance of the cablebolts was analyzed numerically while varying lengths and fixing conditions. The supporting effecte is assessed by monitoring displacements and stress taken place in shotcrete. When cablebolts are grouted without being tensioned, supporting effect was not as good as that of rockbolts. But, their supportability was good enough to substitute rockbolts if tensioned properly. Post grouting right after tensioning of the cablebolts shows reduction in supportability, but long term stability could be achieved without losing supportability if grouted when the bolt is far enough from the face. Further study is necessary including laboratory and in-situ tests under various conditions to use cablebolts as main support in tunnels.