AbstractBasement excavation will cause installed piles to move laterally. It is very common for driven piles in developments with two-level basements to have large eccentricities from their intended positions at the cut-off level of the piles. However, this naturally occurring phenomenon is not well recognized in the construction industry. This is evident from the fact that the allowable pile eccentricity specified in many technical specifications for developments with basements is fixed at 75 mm, which normally is specified for pile foundations of developments with no basement construction. This paper used a case study to illustrate the extent of such pile lateral movements as a result of basement excavation. The effect of such lateral movements on the pile foundation design was discussed using the case study. Appropriate allowable pile eccentricity for driven piles for developments with deep basements are proposed.Practical ApplicationsIt generally is known that excavation for basement construction causes large lateral movement of preinstalled piles. However, the allowable pile eccentricity for single piles and pile groups specified by most practicing engineers is appropriate for developments without basements. This means that the risks for a large pile’s lateral movement as a result of the excavation are borne by piling contractors, even though to a large extent such risks are beyond the control of piling contractors. The findings of this study are useful for practicing engineers to specify the allowable pile eccentricity for single piles and pile groups in developments with basements to achieve a fairer risk allocation for piling contractors and developers. The ultimate aim is to achieve a more competitive piling cost for developments with basements, because piling contractors do not have to price for risks that have been allocated unfairly to piling contractors.

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