Reinforced concrete rock sheds are usually covered by a layer of soil as a shockabsorbing cushion. To better understand the damping abilities of this cushion in order to estimate the impact action. an experimental study has been carried out. Blocks simulating falling rock blocks were dropped from various heights on a reinforced concrete slab covered by different fill materials. After describing the tests and measuring devices, the experimental results are analysed and mathematical expressions for some of the problem variables are presented.
SUMMARYA model was developed, to describe miscible grout propagation in a saturated deformable porous medium, based on Bear's statistical model with spatial volume averaging. In a previous paper, the model was "rst successfully confronted to one-dimensional laboratory experiments.In the present paper, the numerical model is used to simulate practical grouting operation in a cylindrical injection model. The cylindrical injection model lends itself to study main #ow and propagation characteristics for a dispersed suspension-type grout, under axisymmetric conditions close to real scale conditions.Comparison between numerical solutions and experimental results is essential to con"rm the validity and accuracy of the proposed model from a phenomenological standpoint. The numerical model performances show that the underlying mathematical model constitutes a realistic predictive model reproducing most prominent features during injection of a suspension-type grout into a deformable porous medium. The basic mechanism by which injected miscible grout permeates a soil mass is discussed in detail. Such a tool leads to quality control criteria for grouting on a theoretical basis, which complements existing criteria acquired through engineering practice.
Étude expérimentale de la chute de blocs rocheux sur une dalle en béton armé recouverte par des matériaux amortissants Résumé Le dimensionnement des galeries de protection contre les chutes de pierres dépend fortement de l'estimation des sollicitations dynamiques, que l'utilisation d'une couche amortissante peut réduire considérablement. Afin d'approfondir les connaissances actuelles sur les capacités d'amortissement des matériaux meubles, une étude expérimentale a été menée au Laboratoire de Mécanique des Roches de l'EPFL : des blocs de 100, 500 et 1 000 kg ont été lâchés de diverses hauteurs (≤ 10 m) sur une dalle en béton armé recouverte par un remblai d'épaisseur variable constitué de trois types de matériaux différents. Les dispositifs et programme d'essais sont tout d'abord présentés. Ensuite, un exemple complet permet d'illustrer les divers enregistrements effectués lors d'un impact, ainsi que les traitements postérieurs à celui-ci. Finalement, une analyse des résultats expérimentaux souligne les principales tendances entre les grandeurs mesurées et débouche sur l'élaboration d'expressions mathématiques entre certaines de ces variables.
This is the accepted author's version of an article protected by copyright. The rights are held by Springer-Verlag Wien.The final publication is available at http://link.springer.com. Summary During the crossing of brittle rock formations at the Lötschberg base tunnel, failure phenomena have been observed both at the tunnel face and at the walls. A detailed analysis has been undertaken to explain these behaviours, based on the recent developments of Canadian research on brittle failure mechanisms. At the tunnel walls, a very good agreement is found between calculated and observed damage and between two prediction methods i.e. a semi-empirical failure criterion and elastic calculations with the "brittle Hoek-Brown parameters". Near the face, due to the 3D nature of the stress conditions, some limitations of these approaches have been highlighted, and the growth of wall failure has been analysed. This research allowed a better understanding of the brittle rock mass behaviour at the Lötschberg base tunnel and showed that brittle failure processes dominate the behaviour of deep, highly stressed excavations in massive to moderately jointed rock. It also illustrates where improvements to the adopted approaches are required.
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