TA project: SMELI

Click here to read the final report of the SMELI Project.

A concise presentation of the project's aim and main outcomes is available in the Joint brochure of the SERIES TA facilities.

TITLE OF PROPOSAL: The Dynamics of Soft Media Reinforced with Long Inclusions

EQUALS, Bristol, UK

March 2010

March 2010

July 2010

NO. OF USERS (researchers):

Claude Boutin - Ecole Nationale des Travaux Publics de l‟Etat (France)

Stéphane Hans - Ecole Nationale des Travaux Publics de l‟Etat (France)
Jean Soubestre - Ecole Nationale des Travaux Publics de l‟Etat (France)
Marek Lefik - Technical University of Lodz (Poland)
Marek Wojciechowski - Technical University of Lodz (Poland)
Loretta Batali - Technical University of Bucharest (Romania)
Horatiu Popa - Technical University of Bucharest (Romania)
Jonas Thor Snaebjornsson - University of Iceland
Ragnar Snaebjornsson - University of Iceland 



Dynamic response of structures founded on group of piles remains difficult to understand due to the complexity of the interactions between the components of the system made of deep piles, soil and structure. Yet, this solution remains preferable especially for structures founded on soft soils. Understanding the behaviour of these complex systems represents a common research objective and interest for all the present team members who gather researchers from different countries with high or very high seismic activity like France, Romania, Poland and Iceland.
To describe these systems under dynamic loadings, a study based on homogenization has been initiated in the laboratory LGM/DGCB of the ENTPE/CNRS (Université de Lyon). Materials are assumed linear elastic as usual in geophysics under sufficiently small deformations. This approach accounts for the pile group effect (soil is reinforced by a periodic distribution of linear inclusions) and includes the key physical parameters, i.e. the stiffness soil/pile ratio and the dimensions and the density of the piles lattice. The Technical University of Lodz team has an alternative approach by using artificial neural networks models. The Technical University of Civil Engineering Bucharest, Romania has an interest in numerical modelling of the problem, while the University of Iceland research group studied the behaviour of similar complex geological systems through in-situ vibration measurements.
Following these theoretical, numerical and in-situ approaches, it would be timely to proceed to small scale laboratory experimental validation. The unique earthquake testing facilities existent at University of Bristol (shaking table/shear box) provide an excellent environment for advanced dynamic studies of these complex systems. A number of careful designed experiments on an analogue material unreinforced and reinforced with linear (vertical) inclusions are proposed. The experiments naturally include the pile group effect usually present in practice and the analysis of the response in the spectral domain should provide valuable information on the actual bending effect due to the reinforcement under transverse motions. Variation of the key physical parameters should allow the assessment of the influence of the reinforcement on the foundation impedance. The need here is to study the phenomenological aspects of the problem through a physical set-up that has appropriate stiffness contrasts and the like, which is sufficient to evaluate the underpinning assumptions of the homogenisation concepts and analytical models. Therefore, the physical models need not be strict scale models of an exemplar foundation situation.
The aim is to form a team with complementary knowledge in order to share competences and to develop: 1. Experiments with shaking table, 2. Theoretical and analytical modelling of experiments, 3. Numerical modelling of reinforced soils.
In addition, not part of the SERIES but logical follow on of the proposed research, further in situ experiments on geological structures with high contrasts of stiffness will be conducted. The idea is to attempt, through ambient noise vibration measurements, a validation of the theory (and of shaking table small scale experiments).

What's next

Series logo small   SERIES Concluding Workshop
  Joint with US-NEES "Earthquake Engineering Research Infrastructures

Follow us