Experimental study on the progressive collapse mechanism of excavations retained by tied-back retaining systems

Progressive collapses of tied-back excavations caused by the failure of some anchors often occur. However, the mechanism through which partial failure evolves to global failure and how the local failure rate influences progressive collapse has not been investigated. In this study, anchor failure experiments involving tied-back excavation were designed to explore the load transfer path and rule in the case of partial anchor failure. The results showed that, anchor failure leads to an increase in the axial force on adjacent anchors, an increase in the maximum bending moment of capping beams, and easy damage in capping beams due to structural reinforcement. The lower the anchor elevation is, the greater the excavation depth, and the greater the load transfer coefficient (axial force). The failure rate of anchors has an effect on the stress redistribution of the structure and the soil arching effect. In multi-row anchored pile retaining excavations, more rows of anchor failure could trigger the remaining anchors failure because the load transfer coefficient (axial force) is greater for these anchors, which leads to large-scale excavation collapse.