Abstract

Design of piles in chalk is considered as an important issue for a number of geotechnical applications in Northern Europe. Few methods exist for predicting the ultimate axial pile capacity in chalk, but little guidance can be found regarding the design of driven piles in this complex material as experience is rather limited. This paper aims to study the short and long-term predictive performance of different pile design methods used in France and the UK where chalk is found widespread in the north-west coast and the south-east coast, respectively. Conventional methods used in France and the UK are compared by considering seven full-scale static load tests performed in Paris Basin and extracted from the LCPC pile database. The ratio of the measured vs calculated pile shaft resistance and base resistance value is analysed and the scatter of each method is studied. The comparison shows large differences between results. Extension of the database is of great importance to improve the predictive reliability. The last part discusses the evolution of the long-term capacity of driven piles in chalk due to ageing effects. Results show an increasing trend after driving, following a hyperbolic evolution curve.

摘要

粉笔桩的设计被认为是北欧许多岩土工程应用中的重要问题。很少有方法可以预测粉笔的极限轴向桩承载力，但由于经验有限，因此在这种复杂材料中设计驱动桩的指导很少。本文旨在研究法国和英国使用的不同桩设计方法的短期和长期预测性能，而法国和英国分别在西北海岸和东南海岸发现了白垩。通过考虑在巴黎盆地进行的七个全尺寸静态载荷测试并从LCPC桩数据库中提取出来的方法，比较了法国和英国使用的常规方法。分析了测得的桩轴电阻与计算得出的桩身电阻与基础电阻值之比，并研究了每种方法的分散性。比较显示结果之间存在很大差异。数据库的扩展对于提高预测可靠性非常重要。最后一部分讨论了由于老化效应导致的白垩中打入桩的长期承载能力的演变。结果表明，驾驶后遵循双曲线演变曲线呈上升趋势。