Pile Behavior Due to Excavation-Induced Soil Movement in Clay. II: Collapsed Wall

A series of centrifuge model tests has been conducted to investigate the behavior of a single pile behind a retaining wall that eventually fails due to soil excavation in front of the wall. All the piles are located at $3\mathrm{m}$ behind the wall where the soil experiences large shear strain $(>2\%)$ . The induced bending moment and deflection on the pile as well as the soil and wall movements are monitored at regular intervals throughout the tests. It is found that the pile performance depends greatly on the degree of wall instability. After a critical excavation depth, active wedge slip plane and tension cracks developed in the vicinity of the pile. The limiting soil pressure profile deduced from the measured maximum induced pile bending moment profile is established to be much lower than that of a conventional laterally loaded pile. Using the measured soil movements at the pile location as the input data, the calculated pile bending moment obtained using an existing numerical model generally show fair agreement with the measured values when the back-analyzed limiting soil pressures acting on the pile are employed in the back-analysis. The practical implications of the findings are discussed in the paper.