Restricted accessResearch articleFirst published online 2018-6
The spalling limit in transversely isotropic materials,the prediction of the maximum height of failure,and the design of long-tendon roof support systems
In bedded sedimentary rocks with low strength relative to the stress conditions the maximum height of failure above roadways and tunnels can be predicted using the spalling limit concept and a parameter to address transverse isotropy. For siltstones and mudstones a spalling limit of 50° and Young's modulus/independent shear modulus ratio of 100 can be used for roof support design. Using this failure criterion, simple design charts can be produced to provide an appreciation of the roof support requirements in various mining situations. Bulking factors can be applied to the predicted failure heights to provide roof deformation triggers.
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