The rock massif strengthening using micro-reinforced shotcrete (MRS) with polypropylene fibers and prestressed bolts of high rigidity is presented in the paper. The results of carbonate rock complex classification and those obtained by geotechnical laboratory testing of rock samples and micro-reinforced shotcrete, including results of the in situ testing of the strengthened massif's mechanical properties are equally provided. A numerical analysis of a strengthened rock slope over 40 m in height and inclined to approx. 85° was also made and is presented in the paper.
L'amelioration d'un massif rocheux par beton projete micro-arme à fibres polypropylènes et par ancres precontraintes est presentee dans le present ouvrage. Les auteurs presentent les resultats de classification du complex carbonatique rocheux, les resultats des essais geotechniques en laboratoire effectues sur les echantillons du massif et sur le beton projete rnicro-arme, ainsi que les resultats de l'analyse des caracteristiques mecaniques du massif après amelioration. La simulation numerique du massif rocheux incline à environ 85° et de plus de 40 m d'hauteur a egalement ete effectuee.
Im Artikel wird eine Verbesserung des Gesteinmassivs mittels Spritzbeton, mikrobewehrt mit Polzpropzlenfasern, und vorgespannten steifen Ankern dargestellt. Prasentiert sind die Ergebnisse der Klassifikation des Karbonatgesteinkomplexes, der geotechnischen Laboruntersuchungen der Gestein- und Spritzbetonproben, sowie "in situ" Untersuchungen der mechanischen Eigenschaften des verbesserten Gesteinmassivs. Eine numerische Simulation des verstarkten Gesteinhangs mit Neigung von cca 85° und ueber 40 m Höhe wurde durchgefuehrt.
The water required by the town of Rijeka has been taken from the water-pumping site Zvir since 1894. This site is presently the axis of the town's water supply system as it provides approx. 70% of all required water in the dry season. However, the capacities of the existing pumping station are limited and can no longer meet the growing water-supply needs of the town. In order to resolve this problem, a team of experts prepared in 1987 a study for the construction of a new pumping-station structure. At that, it was necessary to examine the stability of the water- pumping site, since a roof structure was initially built above the basin and the high and steep rock slope above the Zvir site in the Rječina canyon has on several occasions been "strengthened" by concrete. Several attempts have been made over the last hundred years to ensure the local and, to some extent, the global stability of the slope. However, the local and global stability of the slope still remained inadequate and, for that reason, the main design involving the reinforced-concrete grid composed of horizontal and vertical girders was prepared in 1988. Due to the great quantity of the work and material required to build the grid structure (table 1), it was finally decided to adopt the system of rigid prestressed bolts with reinforced concrete bolt heads which fit harmoniously into the natural environment. In addition, the new design elements are much more rational than those proposed in the previous solution (table 1).
The slope above the Zvir pumping station is mainly composed of the well bedded Upper Cretaceous limestones and dolomites. The dolomite occurrences have been registered in the retaining wall zone (macroblock I). The Zvir water-bearing site was formed in the tectonically very mobile area where the carbonate mass moves with a relative ease along the plastic surface (mainly composed of flysch). Small changes in pressure directions are sufficient to cause cracking and rotation of macroblocks, so that reverse faults, sometimes of considerable size, are formed in boundary zones. The rotated tectonic blocks become deformed and finally crack thus forming variously fissured and oriented microblocks.