What is Dynamic Sampling?

February 12, 2025

The meaning of words and phrases seem to be continually changing and evolving within both our social lives as well as our work lives and the use of the term ‘dynamic sampling’ is amongst these. Unfortunately, where this occurs and where multiple meanings of the same phrase occur this can lead to misunderstandings or confusion. In order to reduce these misunderstanding and confusion the Training and Education committee would like to clarify the BDA position with regard to the use of the term ‘dynamic sampling’.

The term ‘dynamic sampling’ was derived from the first publication of BS EN ISO 22475-1 in 2006, where the term ‘dynamic driving’ was used to describe a technique to drive certain samplers including window samplers. The first significant use of the term ‘dynamic sampling’ in the UK is within the Land Drilling Vocational Qualification (VQ) developed by the BDA also in the mid-2000s. The term was used in the qualifications to identify the specific but very different skills and knowledge required by lead drillers using dynamic sampling machines as opposed to cable percussion, rotary or sonic machines. This approach tied in with the growing popularity of the Dando Terrier and Archway Competitor sampling rigs which were used to dynamically drive sampling barrels into the ground.

The British Drilling Association (BDA) has played a pivotal role in shaping industry standards and best practices related to dynamic sampling. As the leading representative body for the drilling sector, the BDA has long recognised the need for clear, consistent terminology to ensure both safety and technical accuracy across geotechnical and environmental investigations. The development of the Land Drilling Vocational Qualification (VQ) in the mid-2000s, was a direct response to this need, distinguishing the specific competencies required for dynamic sampling operations. Furthermore, the BDA’s publication of guidance on the Safe Operation of Dynamic Sampling Rigs and Equipment in 2007, sought to unify industry understanding of the method and associated machinery. Today, the BDA remains committed to reducing ambiguity by updating its guidance and championing the adoption of precise terminology, reinforcing its dedication to professional standards and operational clarity within the drilling community.

In the decade prior to the standard and VQ, window sampling had become an accepted sampling method in the UK especially for limited access sites such as infrastructure slopes where the typical equipment would be handheld. The sampling barrels were initially entirely window sampling barrels (hollow steel barrels with slits cut out along one side) and the term used is completely relevant to the equipment. In the early 2000s sampling barrels incorporating a semi-rigid liner started to become popular and steadily replaced the predominantly handheld window sampling barrels. However, the original term of window sampling was often adopted to describe not only the method but also the equipment and sample obtained even if window sampling barrels were not used. As liner sample barrels became more common the term ‘windowless sampling’ was unfortunately adopted to differentiate when using the new type of sampling barrels. In order to try to recognise a common technique to incorporate both window sampling and liner (windowless) sampling, the term ‘dynamic sampling’ was adopted within the BDA Guidance for the safe operation of dynamic sampling rigs and equipment published in 2007. However, in this document, the term was still used to describe the method and equipment used to ‘dynamically drive hollow steel barrels’. Based on the history of the evolution of ‘dynamic sampling’ and different uses of the terms within documentation and across industry, it is not surprising why there are significant misunderstandings and confusion.

During numerous discussions held by the Land Drilling VQ industry working party and discussion within both BDA and AGS sub-committees there is a unified desire to provide further clarification to the meaning and use of the term ‘dynamic sampling’. It is clear that the industry should define specific terms to differentiate between the machine, methods and equipment. The BDA proposes to amend all of its guidance to reflect that ‘dynamic sampling’ refers to small-tracked machines or demountable (modular) feed frame hydraulic machines which solely or predominantly dynamically drive downhole tooling, including samplers, into the ground. In addition, to further reduce confusion, the samplers should be referred to as either window samplers or liner samplers utilising window samplers or liner samplers, respectively. Although the term window sampling is still relevant solely where window samplers are used, the term ‘windowless sampling’ or ‘windowless samples’ should no longer be used. The term ‘window sample’ should also no longer be used as it is always small disturbed samples which are actually obtained from these samplers.