An experimental study on the performance of Resin-grouted bolts under pull-out tests in laboratory and in-situ environments

Abstract

Abstract Adhesive anchors are widely used in geotechnical engineering, yet few studies compare resin systems under matched conditions in both laboratory and field settings. This study evaluates the tensile capacity, governing failure mode and failure mechanisms of epoxy and vinyl ester adhesive anchors. A programme of 240 monotonic tensile pull-out tests was conducted at the University of Johannesburg and at Northam Platinum’s Zondereinde Mine in the Bushveld Igneous Complex, South Africa, across eight configurations using bolt diameters of 10 to 24 mm installed in concrete and in weathered norite and gabbronorite. One representative record was retained per configuration, and all reported quantities derive from measured load. Capacity was frequently governed by the steel anchor rod rather than by the resin bond: five of the eight configurations reached or exceeded the rod yield load, so their reported bond stresses are lower bounds. Where bond capacity could be measured at matched geometry, the epoxy system was stronger, yielding 6.47 MPa against at least 9.45 MPa at 160 mm embedment and 6.24 MPa against at least 7.15 MPa at 245 mm embedment; the epoxy bond was not brought to failure in any configuration. The vinyl ester system developed at least 11.14 MPa in weathered rock, compared with a measured 6.24 MPa in concrete at comparable embedment, and mobilised full steel capacity at 250 mm embedment, whereas the epoxy system required 350 mm. Interpreting pull-out results without reference to steel utilisation risks, attributing to the resin a capacity determined by the steel.