Luca Zini

Debris Flow Phenomena: A Short Overview?

Debris flows are one of the most dangerous and destructive processes affecting the second order streams in the mountain areas (Cavalli et al., 2005; Boniello et al., 2010; Santi P.M., 2008). This very common phenomenon in the Alpine environment is a type of landslide defined by several authors (Varnes, 1978; Hutchinson, 1988; Pierson, 2005; Pierson and Costa, 1987; Coussot and Meunier, 1996; Hungr et al., 2001) trough focusing on the involved material, on the water saturation and on the mass velocity. Debris flows usually consist of a complex mixture of fine (clay, silt and sand) and coarse (gravel, cobbles and boulders) materials with a variable water quantity (Nettleton et al., 2005). The outcoming mixture has a behaviour similar to a viscous “slurry” with a high density, 60% to 80% by weight solids (Varnes, 1978; Hutchinson, 1988; Pierson, 2005). The same Hutchinson (1988) is describing them as “wet concrete”. These phenomena are rapid mass movements, gravity induced able to transport large quantities of sediments and wood downslope, producing complex distribution of deposits and eroding surfaces along their flowpath (Remaitre et al., 2003). Several other classifications try to define these processes. For example, Aulitzky in 1982 provided a classification focused on the typologies of the materials involved making a macroscopic distinction between the rocks and the engineering soils. Pierson and Costa, in 1987, proposed their classification basing it on the sediment concentration and on the average flow velocity. Paoluzzi, Coussot and Meunier, in 1996, described debris flow as a function of sediment concentration and material typology, between hyperconcentrated flows and landslides. Celerity, deposit nature and flow type are the parameters considered. Two of them are appropriate for a practical classification: solid fraction and material type (Paoluzzi et al., 1996). Hungr in 2001 (Hungr et al., 2001) elaborated a classification having as main distinctive parameters the water content, the velocity and the material typology. Seen that existing classifications for landslides were based on process, morphology, geometry, movement type and rate, type of material and activity, in 2005, Jakob (Jakob, 2005) proposed a different categorization based on a size classification. This classification is rarely used because it provides too little information on morphology or process characteristics of a landslide. It has been prevailing studied for regional studies along infrastructures corridors because it addresses variables that are part of a hazard evaluation. Anyway, in the present work, a simple criterion of identification is proposed. Debris flows must be seen as intermediate phenomena between hyper concentrated flows (intense bed

Recognition and strength characterization of platy limestone layers in the Classical Karst quarries (NE Italy)

This paper shows the results of research investigations carried out along the karst plateau located in the Trieste and Gorizia counties (NE Italy), with special emphasis on limestone quarries. Field surveys allowed the recognition, identification and mapping of quarries characterized by the presence of Platy Limestone (PL). The latter is characterized by a single discontinuity set with spacing not exceeding 10 cm. For this reason, the geometry of PL rock masses provided, for a long time, slabs easy to be excavated. PL was widely used by locals for roofs of buildings situated mainly in the rural surroundings of Trieste. The research envisaged a multidisciplinary approach, which also included the definition of the main geometrical features of PL quarries, the state of activity and the geotechnical properties of PL rock mass. Particular attention was devoted to the definition of PL intact rock strength, which is major rock property. Intact rock strength determines the strength of the rock slab and therefore its geomechanical quality. The outputs of this paper can motivate local authority to protect PL and promote its use for the restoration of historical buildings