Understanding the mechanical mechanisms underlying the group anchoring is essential for reinforcing earthen sites in arid regions of northwest China. In this study, a full-scale rammed earth model with stratified structural was established, followed by pull-out tests on single-, double-, and triple-anchor. From the test results, a numerical model incorporating interface elements was developed and validated, which was further employed to extend the analysis of the failure mechanisms of group anchors. The results reveal that the failure mode of anchor group involves a composite mechanism comprising cone-shaped collapse of the rammed earth and debonding at the anchor-grout interface. The failure zone expands exponentially with increasing anchor number, and the failure surface exhibits marked asymmetry. Group anchoring induces a nonlinear reduction in bearing capacity, with failure of the leading anchor significantly degrading the load performance of subsequent anchors. Load-displacement curves exhibit four distinct stages, with pull-out capacity primarily mobilized during the plastic sliding phase. Numerical simulations systematically elucidate a coupled failure mechanism involving shear failure at the anchor-grout interface and tensile failure along the rammed-earth layers. These findings provide a quantitative framework for evaluating group anchorage in earthen sites conservation and guide further research on anchor-soil interaction mechanisms in heterogeneous soils.