Experimental Study on the Influence of Support Failure on Remaining System Under Asymmetric Excavation

To investigate the impact of localized failure in the support structure on the overall safety performance of the excavation pit and the mechanism of subsequent chain failure, model tests were conducted on the failure of internal bracing in an asymmetrically excavated pit. Unlike previous progressive-collapse model tests, which have addressed symmetric excavations only, the present test captures the cross-pit load-transfer mechanisms that arise when the two sides of a pit are excavated to different depths. The crown displacement of the retaining structure, the earth pressure, and the redistribution of internal forces caused by the failure of internal support members were measured. The results show that when an internal support fails, the lateral stiffness of the retaining plate decreases and the plate moves inward toward the pit, causing settlement of the surrounding soil. The horizontal displacement on the deep-excavation side is larger than that on the shallow side. Failure of one support increases the axial force in the adjacent support while reducing the force in supports farther away. The earth pressure increases in regions far from the failed support, owing to the soil arching effect, but decreases in the adjacent region because the large lateral movement of the plate unloads the soil. Within the failed-support region, the retaining piles are more prone to bending failure on the shallow-excavation side.