I am a PhD research student working in the field of geotechnical risk analysis, particularly looking at quality assurance of bored pile foundations.
From the design engineers point of view, the aim of low-strain pile integrity testing is to provide an acceptable level of evidence, at minimum cost and time to the contract, that the individual foundation piles that have been constructed meet their design specification in terms of structural integrity and are therefore likely to perform as intended in operation.
In the UK, the number of piles to be tested is a matter for the engineer to decide based on site specific knowledge, experience and engineering judgement. In the absence of official guidance, the industry tends to favour 100% inspection, that is, testing every pile on-site. However, when such a strategy is impossible to perform, for whatever reason, the quality of a pile population may be inferred through sampling inspection.
I am extremely interested in learning about the different international practices regarding the programmes of low-strain integrity testing implemented for quality control of bored, cast-in-situ piling. I believe that the percentage of piles tested varies significantly in different countries, therefore the questions I pose for discussion are;
a) What percentage of piles should be integrity tested to give an acceptable assurance as to the construction quality of an entire piled foundation?.
b) What factors are taken into account or what methodology is adopted in deriving the percentage of piles tested on a given site?.
Any replies to my questions would be most appreciated. Many thanks.