This year, the Comité Français de Mécanique des Sols et de Géotechnique (‘French Committee for Soil Mechanics and Geotechnics’) has invited Alain Holeyman to speak at the Coulomb Conference. The invitation is recognised as a major scientific award in the field of geotechnics.
It’s a tradition established by the Comité Français de Mécanique des Sols et de Géotechnique (CFMS): a scientist whose research has propelled a major advance in the field geotechnics is invited to present his work at the Coulomb Conference. In 2017, the honour belongs to Professor Alain Holeyman of the Louvain School of Engineering.
Diving beneath the visible
Like an iceberg, a work of art presents a visible aspect – the structure – and an invisible aspect – the foundation on which it sits. Without a solid foundation, even the most well-conceived or aesthetic structure has no chance of enduring. What’s underneath, the interaction between construction and environment, has fascinated Professor Holeyman since he started studying civil engineering. ‘The foundations that support a building or a bridge, for example, and the soils and their characteristics, which we have to know well in order for the foundations to play their stabilising role, interested me from the start’, explains this scientist specialised in geotechnics, the field of study of the layer closest to the surface of the earth – whether on land or under the sea – and in direct contact with the built structure.
Research with a human dimension
The best thing about the field is that it’s at the heart of questions concerning mobility and social cohesion: ‘Building a bridge or most any public infrastructure benefits everyone. How we think about the construction is important to everyone’s daily life. That’s a challenge that interests me greatly. Furthermore, for each of these projects, we have to think about the natural setting in which the construction is inserted. This natural setting often presents a massive never-ending challenge.’ Within this context, Professor Holeyman has dedicated his career to two specific subjects: the geoenvironment and geodynamics.
Soil behaviour under extreme conditions
After dedicating several years to environmental issues, Professor Holeyman took an interest in soil geodynamics, especially how soils react to extreme stress. ‘For example, how will soil react to an earthquake and what will be the impact on foundations? To answer these questions, we have to study the interaction between three media that make up different soil layers: solid, liquid and air media react differently to stress.’ He finds the subject as complex as it is fascinating.
A closer look at piles…
Of particular interest to Professor Holeyman are foundations on piles, which are used to support structures on unstable ground by penetrating more deeply to more stable layers. ‘For several years, my research focused on ways to place piles in the ground. It may not be obvious to the uninitiated, but this part of the work is very important, because it determines the structure’s stability and is very expensive and risky given the equipment required to carry it out. To study the placement of piles, we developed a remarkable device in our laboratory that enables us to conduct the necessary tests.’
…and pile-driving
The main technique he studied is pile-driving: driving piles into the ground by striking them with great force. But it’s not about using just any heavy object to hammer away on the pile; precise calculations are necessary. ‘There are two steps. The first is to calculate the depth to which the piles must be driven, regardless of the conditions to which the ground will be subjected. The second is to calculate the driving force. It must be enough to penetrate the ground while remaining inferior to the pile’s structural limit.’
A fondness for offshore piles
In recent years, Professor Holeyman has focused on using this technique to install offshore wind turbines. ‘These wind turbines are much more effective than land-based turbines and more accepted by the public. But the demands are different. For example, the piles often have to be driven some 30 metres into the seabed, whereas only 15 metres is necessary on land.’ His solution is using hollow steel piles that encounter less resistance and become ‘filled’ with the soil or rock into which they’re driven, rendering them just as strong and stable as an originally solid pile. ‘The challenge with solid rock is knowing just how hard we can drive the pile without damaging it. Working on this type of highly technical problem doesn’t make me forget that the final result serves society. That’s very important to me.’
Elise Dubuisson
A glance at Alain Holeyman's bio
1975 : Master’s Degree in Civil Engineering in Construction, ULB
1977 : Researcher, Belgian Building Research Institute (BBRI), Brussels
1984 : PhD in Applied Science, ULB
1985 : Director of Research and Development, Franki International, Liège
1986 : Verdeyen Award
1987 : First Prize, ICE Competition
1994 : De Beer Award
1995 : Associate Professor, UCL, Louvain-la-Neuve
2001 : Professor, UCL, Louvain-la-Neuve
2001-2005 : President, Groupement Belge de Mécanique des Sols et de la Géotechnique (GBMS)