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Thermo-Hydro-Mechanical analysis of Soil-Vegetation-Atmosphere Interaction

Sahar Hemmati
Abstract : The aim of this work is to study, by a two-dimensional numerical approach, the effect of soil-vegetation-atmosphere interaction and water uptake by roots of isolated trees on the thermo-hydro-mechanical behaviour of the swelling-shrinking clayey soils. The case of soil-vegetation-atmosphere interaction is studied based on the data obtained on the Mormoiron site, instrumented by BRGM with Humitub capacitive probes and extensometers. Exploitation of the water content data needed the calibration of the Humitub probe, which constitutes an experimental work performed in the laboratory. The calibration is performed on different materials. The influence of the variations of the temperature and also the effect of soil type on the measurement of the water content are studied. The results seem to show that the capacitive probes like Humitub are not adapted for the clayey and carbonated soils, like Mormoiron clay. The bibliographic studies showed the important dependence of the measurements done by the capacitive method to the frequency, particularly in the case of the soils with a high ion exchange capacity. A two-dimensional soil-vegetation-atmosphere model and a two-dimensional root water uptake model are developed in order to describe the climatic and vegetal effects on the thermo-hydro-mechanical behaviour of an unsaturated medium. These models are implemented in the θ-STOCK finite element code (Gatmiri, 1997). The verification of the soil-vegetation-atmosphere interaction model is done based on a comparison of the calculation results with the in-situ data available on Mormoiron site and meteorological data of the Carpentras station. The calculations are then extended to the particularly dry and particularly moist periods. A longer period of 20 years is also modelled. The root water uptake model is verified on some case studied reported by Biddle (1998), using the meteorological data of London station end considering the effect of soil-vegetation-atmosphere interaction on the soil surface. The obtained results show the pertinence of the adopted numerical approach. This modelling study is finally completed by considering a shallow foundation of a light building. The obtained results clearly show the role of the presence of a tree, and also the importance of its distance from the building on the soil settlements.
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Submitted on : Friday, December 4, 2009 - 8:00:00 AM
Last modification on : Friday, December 4, 2009 - 8:00:00 AM
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Sahar Hemmati. Thermo-Hydro-Mechanical analysis of Soil-Vegetation-Atmosphere Interaction. Engineering Sciences [physics]. Ecole des Ponts ParisTech, 2009. English. ⟨pastel-00005609⟩

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