Tony Barley, CEng, BSc,MSc,MICE, FGS. This paper was first published in GE’s September 1988 edition.
An anchor construction and design manual of the late 1960s opened its rock anchors section with the firm pronouncement. Anchors installed in wet or weak rocks such as marls, mudstones, shales and sandstone, and all anchors requiring loads of greater than 50 tons working capacity, should be constructed with underreamed enlargements. The enlargements, filled with grout, form a positive lock even in soft, weak or wet strata.