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Today, two-component grout is the most widely used backfilling technology in shielded mechanized tunneling. Despite its intensive use, however, very scant information pertaining to the durability of this material is available in the scientific literature. In this work, the aging of two-component grout is studied by curing grout samples using three different modalities. Furthermore, the action of air on two-component grout is studied by assessing the dehydration process, which is a phenomenon that occurs when the material is cured without being completely embedded in soil/rock. Uniaxial compression tests and three-point flexural tests have been carried out for mechanical characterization. The results reveal that in a curing environment made of sand, a moisture of 5% is sufficient to guarantee correct curing of the grout and extend the mechanical performance to three years, whereas the action of air is potentially dangerous, since the grout suffers strongly from dehydration. Despite this dehydration process, however, the mechanical performance of the grout also tends to increase for samples cured under the action of air until a very high level of cracking and shrinkage is reached. A discussion of the limitations on the uniaxial compression strength as the main mechanical parameter for the characterization of two-component grout concludes the work. [ABSTRACT FROM AUTHOR]

The installation of draped meshes, metallic nets installed in such a way as to lie against the rock slope surface, is one of the most common ways to protect roads and infrastructure against the detachment of small rock elements in areas prone to rock fall. Despite their frequent and worldwide application, there are no universally recognized guidelines or technical standards to help engineers in their correct design, and no full-scale test results are available where the whole system, composed of several interacting structural components, is tested. In this paper, a full-scale test procedure, which is able to permit the evaluation of the global behaviour of a draped mesh, is described and the results of tests carried out on widely used meshes are presented and discussed. Key words: rock fall, natural risks, full-scale testing, wire mesh, cable net. L'installation de maillage drape, des filets metalliques installes de maniere a reposer sur une surface rocheuse en pente, est une des methodes les plus courantes de proteger les routes et les infrastructures contre le detachement de petites roches dans les zones propices aux eboulements. Malgre leur utilisation frequente et repandue a travers le monde, il n'y a pas de normes ni de standards techniques pour assister les ingenieurs dans le choix de la conception appropriee. Aucun resultats d'essais a l'echelle reelle, comprenant le systeme complet compose de plusieurs elements structurants integres, sont disponibles. Dans cet article, une procedure d'essais a l'echelle reelle qui permet l'evaluation du comportement global d'un maillage drape est decrite et les resultats des essais effectues sur des grillages typiquement utilises sont presentes et discutes. Mots-cles : eboulements, risques naturels, essais a l'echelle reelle, grillage metallique, filet de cables. [Traduit par la Redaction], Introduction Small rock fragments and single rock blocks, with sizes between 0.01 and 1.5 [m.sup.3], that detach from slopes overhanging roads and railways create one of the most frequent hazards [...]

Earth pressure balanced (EPB) full face tunneling machines have experienced a remarkable increase in the number of applications throughout the world due to both mechanical developments and a more effective use of additives to condition the ground. Conditioning modifies the mechanical and hydraulic properties of a soil by making it suitable for the pressure control in the bulk chamber and extraction with the screw conveyor. The extraction system plays a fundamental role during the EPB operations particularly for a correct application of the face pressure. Despite the extensive use of the EPB technique, little knowledge exists concerning the understanding of the behavior of conditioned soil, particularly for noncohesive ground (sand and gravel). This paper presents and describes a prototype laboratory device, which simulates the extraction of the ground from a pressurized tank with a screw conveyor. The results of a preliminary test program carried out on a medium sized sand show that the prototype device is efficient in verifying the effects of foam for an optimal use in EPB conditioning. CE Database subject headings: Tunnelling; Foam; Laboratory tests; Soil properties.