关键词: 灌注桩, 桩底沉渣, 失效概率, 可靠度, 桩承载力

Abstract: Defects present in a pile may not always be detected by integrity tests, which will adversely affect safety of the pile. This paper aims to propose a methodology to quantitatively evaluate the reliability of pile foundations considering the possibility of pile defects presence. Taking the toe debris present in a single pile for example, the probability of failure of the pile considering the possibility of toe debris presence is formulated by integrating the probabilities of failure for an intact pile and a pile with toe debris systematically within the framework of the total probability theory. The pile capacity reduction factor is presented to account for the effect of toe debris on the pile capacity. Moreover formulae for calculating the bias factor and coefficient of variation of the pile with toe debris are derived. The results indicate that the impact of the possibility of toe debris presence on the reliability of piles can be quantitatively evaluated using the proposed method in a rational way. The reliability of the pile is adversely affected by the presence of toe debris. The reliability index of the pile with toe debris decreases with the thickness of toe debris and the pile diameter; and it increases with the pile length. When the possibility of toe debris presence is not taken into account, the safety of the pile is highly overestimated. The reliability of piles can be highly improved with the implementation of pile integrity tests.

Key words: bored piles, toe debris, probability of failure, reliability, pile capacity