Empiricism in geotechnical design

Having practised geotechnical engineering for more than 25 years in several countries, one of the pillars supporting my geotechnical designing has been the understanding and development of empiricism. That is knowledge based on experience, observation or existing data.

When John Burland presented his “Soil Mechanics Triangle” back in his 1987 Nash Lecture, in the context of teaching soil mechanics, he discussed empiricism as inevitable and an essential aspect of soil mechanics. He went on to further explain that many of our design and construction procedures are the product of what might be termed “well-winnowed experience” and if appropriately used are highly reliable. Placing these in the centre of his triangle comprising the ground profile, soil behaviour and appropriate model, he considered that it could prove a valuable aide-mémoire for practising engineers.

Thirty-five years later, as a practitioner, it remains to me a valuable concept to recognise that we continue to idealise ground profiles, soil behaviours and modelling when determining geotechnical design solutions, with the real behaviour of structures being based on empiricism. It’s empiricism that is informing the basis of our everyday engineering judgments and should continue to do so in the future. Well considered case studies published by engineers, which present empiricism, are therefore crucial to practising engineers. But also, only with such empiricism can theory be established to improve and evolve our engineering design solutions.

It is also important that practitioners understand when geotechnical design is routine (i.e., it relies on empiricism) or is innovative (i.e., when we design outside empiricism). Having a thorough understanding of the empiricisms being used is crucial, as such understanding provides a useful demarcation beyond which we can knowingly design innovatively and creatively, and the soil mechanics triangle provides a valuable construct to do so with rigour.

In my career I have enjoyed “parachuting” into major infrastructure projects overseas taking on leading roles in both geotechnical design and construction. I have actively sought out local geotechnical design practices and construction methods to broaden my “well-winnowed experience” and understanding of local empiricism to safely practice routine and innovative geotechnical engineering in those countries. I would highly recommend to mid-career geotechnical designers the value of practising geotechnical design in another country.

First-hand experience can be a great teacher of empiricism in soil mechanics. However, this traditional source of empiricism is expected to be increasingly shared with empiricism based on experience from artificial intelligence and machine learning. Regardless of the future sources of empiricism, I would postulate that it will remain an essential skill for practitioners and researchers in soil mechanics to properly understand the derivation and use of empiricism and to share through publication of well-considered case studies, for the whole industry to develop and innovate.

It is therefore encouraging that the British Geotechnical Association (BGA) has introduced the BGA Case Histories Award for the geotechnical engineering profession. Its aim is to encourage and recognise the importance of publishing well-considered and researched case histories in the exchange of exemplary geotechnical knowledge and experience on the performance of constructed works.

• Chris Barker is an associate director at Arup. He is a fellow of the Institution of Civil Engineers and a member of the BGA executive committee.