Analysis of the End-Bearing Capacity of Piles in Sand Under Limited Region Failure by a Mixed Zero-Extension Line Method

The failure zone around the pile tip varies greatly with the different failure patterns considered in research on the end-bearing capacity of piles. In an effort to improve the consideration of the size of the failure zone, a new failure pattern is proposed in the estimation of the end-bearing capacity of driven piles in sand and the failure zone is determined by zero-extension line (ZEL). Considering a failure zone limited below the pile end plane and an equivalent frictional contact condition with the equivalent frictional strength fully mobilized at the failure zone boundary, a more realistic prediction of the end-bearing capacity of piles is achieved. Reasonable values of parameters are obtained through parameter and numerical analysis. It is found that the failure zone is roughly within the range of 40° from the vertical direction. Comparison between the ultimate toe capacity predicted by the proposed method, a method directly using cone penetration test (CPT) data, and a method based on characteristic theory shows that the mixed zero-extension line method considering limited region failure has a better consistency with experimental data.