Experimental and Theoretical Research on the Bearing Mechanism of Group Anchors in Sand

To investigate the bearing mechanism and efficiency of group anchors in sand, upward pulling tests of model group anchors were carried out for different conditions of the sand density, anchor burial depth ratio, and anchor spacing. The results show that the load-displacement relationships for group anchors is similar to that for single anchors, both being nonlinear for the same relative density and embedment ratio. The load-carrying capacity of group anchors is not a simple superposition of the capacities of two single anchors, but has a clear superposition effect, depending on the relative density, embedment ratio, and anchor spacing. The load carrying capacity increases with the anchor spacing up to a limiting critical value. The bearing mechanism of group anchors was qualitatively analyzed and quantitatively characterized using the strain field and shear stress field obtained through the digital image correlation. Adopting the test data and theoretical derivation, a critical anchor spacing equation is proposed and the relationship between critical anchor spacing, embedment ratio, and relative density is quantitatively characterized. Theory is proposed for predicting the group efficiency of group anchors with different configurations. Comparisons between the results of the developed model and experimental results reported in the literature show good agreement.