Suggested method for rock anchorage testing : ISRM Comm on Testing Methods Int J Rock Mech Min SciV22, N2, April 1985, P71–83

Abstract

(A)This suggested method provides guidelines on a variety of tests for rock anchorages, including design tests and proof tests. In addition, this document suggests equipment, measurements, calculations and records which are suitable for these two classes of tests. The long-term monitoring of anchorages is treated in a separate suggested method. (B) two alternative methods of loading are normally considered in practice. In the co-axial loading method, the rock immediately surrounding the anchor head is used as a bearing surface for the stressing device; thus, rock movement or rock mass failure cannot be tested. Where rock mass failure in the form of a cone, wedge or block is a possibility then the remote loading method is appropriate, whereby the reaction loads are applied via a beam or grillage, to the ground surface remote from the test Anchorage. The span between reaction points must be sufficient to allow rock mass failure, if the rock is weaker than the steel tendon or its bond strength to the rock. For example, if a conical or wedge type of failure is anticipated with an included angle of 45 degrees, the free span should not be less than the total embedded depth. For laminar type failure in horizontally bedded slabby rock, free spans may be increased or decreased depending upon fracture geometry. In cases where the rock is separated from the reaction structure by a considerable thickness of overburden soil, the effect of the overburden's surcharge in restraining rock mass failure must be evaluated. (TRRL)