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Theses

Vieillissement et comportement rhéologique du gypse

Abstract : The underground gypsum mines could show multiple types of instabilities which have major consequences in the surface and in depth. The demonstrations of these disorders are expansions of pillars, ascents of walls, the forming of subsidence. Generally, the old exploited districts are more degraded than the recent ones. To determine the identity, the source and the intensity of gypsum aging, scanning electron microscope observations were conducted on samples located in zones mined during different time periods. Dissolution traces were described on bath crystals faces and extremities. Their origin is probably due to water vapor present in the mining atmosphere. Their intensity decreases with distance from the wall towards the middle of the pillar. The short ti me behaviour of the gypsum was described. Measurements of rooms convergence, pillars expansion and creep tests with controlled hygrometry made it possible to study (in situ and in laboratory) the long term behaviour of gypsum. A coupling hydro-chimico-mechanics was supposed to control the differed deformations. Two mechanisms of differed deformations were proposed : dissolution/migration of water and dislocation. To describe the differed behaviour, a law of long-term behaviour was proposed. The short time behaviour was not taken into account : no instability was noted. The law was based on the unification of the Lemaitre law and Norton law. The good agreement between experimental curves and the simulations showed the capacity of the coupled model to predict the long-term behaviour of the gypsum.
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Christophe Auvray. Vieillissement et comportement rhéologique du gypse. Autre. Institut National Polytechnique de Lorraine, 2003. Français. ⟨NNT : 2003INPL116N⟩. ⟨tel-01749758⟩

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