Abstract: Although collapse cases caused by partial over-excavation are seen frequently, studies on the overall safety performance and the progressive collapse mechanism caused by partial over-excavation are still in lack. In this study, the load transfer mechanism of cantilever contiguous retaining piles of long strip excavation subjected to partial over-excavation were investigated by finite difference method and model test. Results revealed that with the increase of over-excavation depth, the internal force of the piles beyond over-excavation zone increased by a large margin due to soil arch effect, while the bending moment of piles within over-excavation zone increased first and then decreased or continued to decrease. When the excavation depth in a large area remained the same, the increments in bending moment and displacement of adjacent piles intensified gradually and tended to be stable along with the widening of partial over-excavation range. The research results reveal the load transfer rules reflecting the influence of partial over-excavation on internal force of piles.

Key words: excavation collapse, cantilever contiguous piles, partial over-excavation, finite difference method, bending moment of piles