Determination of ultimate resistance of jointed soft rock to pull-out tests on conical anchorages

Conclusion

The jointing pattern of a rock formation determines the internal stress distribution caused by an anchorage being pulled out of it (in the subject case, of conical section), in such a way that the anchorage stability within the rock depends on the forces necessary for shearing of the rock along a cylindrical surface, and not on the cohesion forces between the rock particles along the conical surface as occurs in monolithic rock and cohesive soils; also, the proportion represented by internal friction increases rapidly with embedment depth of the anchorage. The intensity of jointing of rock blocks affects the cohesion value significantly (as the degree of jointing of a rock increases, so the cohesion decreases sharply compared with its value in a monolithic rock), which, in turn, reduces the ultimate resistance to pulling out of an anchorage, and this is well confirmed by the results of full-scale tests, presented above.