Effects of the lateral stress on the inner frictional resistance of pipe piles driven into sand

Janaka J Kumara,Yoshiaki Kikuchi,Takashi Kurashina

doi:10.1186/s40703-016-0015-x

Janaka J Kumara, Yoshiaki Kikuchi + Show 1 more

Open Access

https://doi.org/10.1186/s40703-016-0015-x

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Abstract

The inner frictional resistance of pipe piles depends on the degree of soil plugging. Many factors including pile diameter, lateral stress at the pile tip and geometrical conditions of piles could influence the soil plugging. In this paper, the effects of inner sleeves attached at the pile base on the inner frictional resistance are discussed, particularly highlighting the lateral stresses at the sleeve using small-scale steel pipe piles penetrated into a medium dense sandy ground. A closed-ended pile of the same diameter was also tested to compare it with similar open-ended piles. The results of incremental filling ratio (IFR) and plug length ratio (PLR) were also discussed. A simple method was also proposed to evaluate IFR and PLR for the sleeved piles since they have originally been defined for non-sleeved piles. The results of the IFR indicate that all the piles penetrated under partially-plugged or unplugged state producing smaller penetration resistance than a similar closed-ended pile. The results of the corrected IFR give a better indication of the soil plugging of the sleeved piles, particularly at shallow penetration depths. The results also suggest that the inner frictional resistance increase with the sleeve height. The results of the coefficient of lateral earth pressure, K h also indicate that K h increases with the sleeve height. The effects however become less significant at higher sleeve heights. Therefore, we can recommend the use of the inner sleeve as an improvement method to increase the bearing capacity of open-ended piles installed in sandy grounds.

Highlights

In recent times, open-ended driven piles have gained popularity as deep foundations, in offshore deep foundations due to smaller driving resistance compared to closed-ended piles
Two indexes widely used to describe the degree of soil plugging of open-ended piles, called plug length ratio (PLR) and incremental filling ratio (IFR) are defined in Eqs. 3 and 4 respectively [22, 23]
The effects of the wall thickness on the bearing capacity of the piles used in practice might not be significant compared to the model piles tested in this study due to a slightly smaller ratio of Aan/At (Aan in annular area and At is total area covered by the pile outer diameter)

Summary

Introduction

Open-ended driven piles have gained popularity as deep foundations, in offshore deep foundations due to smaller driving resistance compared to closed-ended piles. Previous studies have shown that the behaviour of open-ended piles is different from closedended piles [1,2,3]. It is accepted that a short open-ended pile produces a smaller bearing capacity than a similar closed-ended pile [4]. A long open-ended pile can produce a similar bearing capacity as a closed-ended pile due to large inner frictional. The ultimate bearing capacity of an open-ended pile consists of three components as given in Eq 1 (see Fig. 1 ). The bearing capacity of an open-ended pile could be influenced significantly by the plug capacity (see Eq 2), which is influenced by the degree of soil plugging

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