The Tower of Pisa started its tilting 5 years after the beginning of its constructionin 1173. Its inclination continued over the centuries. How do we explain this?
The instability of the structure is due to the very soft nature of the ground, and to the foundation type: the tower foundations are only 3 m deep, which is not enough to distribute the load on the heterogeneous soil. At the time, architects didn't have techniques enabling soil analysis.
So you have to spend time and money for something that can't be seen and almost nobody's aware of.
Today, good soil studies and a relevant design of the structure in its environment allow to build high-rise buildings that remain straight!
Presentation by Claude Plumelle, Laurent Briançon and Philippe Gotteland, Curators of the exhibition
Virtual exhibition proposed by CFMS, Syntec Ingénierie, FNTP, USG and ISSMGE.
The Museum of Arts and Crafts hosted the exhibition "Les dessous des grands travaux", a thematic installation on geotechnics proposed by the French Committee of Soil Mechanics and Geotechnical Engineering (CFMS) and its partners. Presented for the 18th International Congress of Soil Mechanics and Geotechnics "Challenges and Innovations in Geotechnics" held in Paris from 2 to 5 September 2013. The installation is a first in France and abroad.Read more
The geotechnical engineer is both a geologist able to diagnose the state of the subsoil, and an architect able to evaluate the properties of a structure and its suitability to the ground. His skills are related to a strong capacity of scientific analysis as well as to an extensive experience, acquired on the construction sites.
He operates in four main areas: buildings, infrastructures (roads, railways, dams ...), natural risk assessment (landslides) and marine constructions (offshore oil & gas).
The French Union of Geologists describes the profession of geotechnical engineer, not according to the disciplines which constitute it, but according to the organisms in which the geotechnical engineer is working. The expertise of a geotechnical engineer in a field will often reflect a particular practice of his profession, and will be different according to the missions he is assigned to:
- Geotechnical engineer as assistant to Owner.
- Geotechnical engineer in a control office.
- Geotechnical engineer as project manager (design office...).
- Geotechnical engineer in a soil testing company.
- Geotechnical engineer in a construction company (contractor).
- Geotechnical engineer in the oil & gas field.
© Sébastien LE PANSE
Soil is composed of solids and cavities full of air and water. The solids are the result of the fragmentation of rock into pebbles, gravel, sand and silt, and also the chemical decomposition of rock into microscopic clay particles.
Water circulates at different speeds depending on the soil’s composition. It circulates freely through permeable soils such as pebbles, gravel and sand, and very slowly through little permeable and even impermeable soils such as silt and clay – water circulates 1 million times slower through clay than through gravel. Soil can contain several concentrations of water, called groundwater, in its underlying strata, the closest to the surface being the water table. The soil in the water table is saturated when all its cavities are full of water.
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