Pull-Out Performance of Rapid-Setting Sulphoaluminate Cement Grout for High-Strength Threaded Anchors in Water-Rich Sandy-Pebble Strata

Anchors constructed in water-rich sandy-pebble strata require grout systems that can maintain material continuity and transfer tensile force effectively before groundwater-related disturbance weakens the borehole interface. This study investigated a sulphoaluminate cement-based rapid-setting grout (SAC) for PSB high-strength threaded anchors, using an ordinary Portland cement-based grout (OPC) as a reference material. Laboratory central pull-out tests were first conducted on grout cube specimens with different steel-bar diameters and bonded lengths to evaluate the steel–grout bond response. Full-scale field pull-out tests were then performed to examine the anchor–grout–ground response under water-rich ground conditions. LS-DYNA finite element models were calibrated against the laboratory and field results to interpret the governing load-transfer mechanism and to assess the influence of representative stratum resistance. The laboratory tests showed that the steel–grout bond response depended on both interfacial degradation and mortar splitting, indicating that peak bond strength should be interpreted together with failure mode and slip development. In the field tests, all anchors failed by pull-out, and the steel bar and grout body were pulled out together, showing that the full-scale response was governed mainly by the grout–ground interface rather than by steel–grout debonding. The calibrated numerical models reproduced the main load–displacement trends and supported a scale-dependent transition from steel–grout bond control at material scale to grout–ground interface control at field scale. The results provide a basis for evaluating rapid-setting grouts for high-strength anchors in water-rich sandy-pebble ground.