F Yu

Base capacity of open-ended steel pipe piles in sand

AbstractThis paper presents a new method for estimating the base capacity of open-ended steel pipe piles in sand, a difficult problem involving great uncertainty in pile foundation design. The method, referred to as the Hong Kong University (HKU) method, is based on the cone penetration test (CPT), and takes into consideration the mechanisms of annulus and plug resistance mobilization. In this method the annulus resistance is properly linked to the ratio of the pile length to the diameter—a key factor reflecting the influence of pile embedment—whereas the plug resistance is related to the plug length ratio, which reflects the degree of soil plugging in a practical yet rational way. The cone tip resistance is averaged over a zone in the vicinity of the pile base by taking into account the failure mechanism of the piles in sand, the condition of pile embedment (i.e., full or partial embedment), and the effect of soil compressibility. The predictive performance of the new method is assessed against a number ...

Improved Evaluation of Interface Friction on Steel Pipe Pile in Sand

AbstractOpen-ended steel pipe piles are now widely used as the foundations for offshore structures. The pile-soil interface behavior is of particular interest in sands where shaft friction plays an important role in resisting the applied load. The rational design of the shaft capacity depends on a good understanding of the mechanisms of interface friction during pile installation and static loading. There are two new methods on the basis of the cone penetration test results that take into account the effect of friction fatigue arising from pile installation. An improvement is made in this study to account for the influence of plugging degree, which is a key issue for open-ended piles. The significance of the modified design framework lies in that it allows for the role of plugging in a more rational way by using the soil-squeezing ratio that is closely related to the radial effective stress and, consequently, the shaft capacity. The performance of the improved method is assessed against the existing metho...

Mechanism and Assessment of Interface Shear between Steel Pipe Pile and Sand

Open-ended steel pipe piles are now widely used as the foundations of bridges. The pile-soil interface behavior is of particular interest in granular soils, because the shaft friction plays an important role in resisting the applied load. Rational design of the shaft capacity depends on a good understanding of the mechanisms of interface shear during pile installation and static loading. There are two new CPT-based methods that are able to take into account the effects of friction fatigue and soil plugging. An improvement is made in this paper to consider the influence of plugging degree on the soil-squeezing ratio which is closely related to the radial effective stress and consequently the shaft capacity. The modified design framework shows better agreement with the field measurements of two instrumented piles than the two existing methods.