The local and extra-regional (national and transnational) stones mainly used as building and ornamental materials in the historic centre of Urbino (UNESCO World Heritage List) were unravelled through a detailed geological and petrographic study. The types of building stones used in the past for the development of an urban centre were mostly affected by the availability of suitable geomaterials in the surrounding areas. For this reason, the stones found in the historical buildings of Urbino generally come from the local sedimentary formations (mostly limestones) belonging to the Umbria–Marche–Romagna Succession Auct., which crops out in the Northern Marche Apennines. Only some ornamental highly prized stones used for monuments and decorations come from both extra-regional Italian areas (Alps, other sectors of the Northern Apennines) and foreign countries (France, Egypt). A brief description of the Northern Marche geology was also reported to exactly match the local provenance of the stones, so highlighting the relationship between the territory and the architecture of Urbino. Because of obvious conservation reasons, no samples were collected from buildings or monuments and only autoptic observations, together with a detailed historical and bibliographic research, were carried out to identify the different materials and the provenance areas. Besides the availability of the local sedimentary rocks, we emphasised how the choice of the building and ornamental stones could have been also influenced by the historic period and artistic style, aesthetic features, economic and social importance of the building and/or monument and the relationship to some distinguished personality (e.g., Pope Clemente XI). An open-air stone itinerary across significant places (10 stops and additional sites and monuments in the urban area) is finally proposed for the best fruition of the geological and cultural heritage of Urbino, also aimed at geotourism development.
This work describes and analyzes the unexpected rockslide that affected, on December 2004, the quarry face of the Ca' Madonna extraction site (Municipality of Urbania, Province of Pesaro and Urbino, Italy), where stratified calcareous lithologies are quarried. This movement occurred in correspondence with an unsurveyed clayey intra-bed layer approximately 10 cm in thickness that consists principally of smectite group clayey minerals. These are very active and have a high capacity to absorb water until reaching a swelling pressure of up to 1200 kPa. Mining activities reduced lithostatic load and facilitated rainwater infiltration down to this bentonitic layer, which led to fully softened conditions (Skempton, 1970) with a resulting severe reduction in the shear strength parameters. Under such conditions, the slope stability back-analysis, performed considering a planar rock slope failure with tension cracks and with different water level heights, shows that a small water level was sufficient to exceed the limit equilibrium. Stratigraphically, this layer can be correlated with the Lower Campanian Bentonitic Layer already reported in other Central Italy sites (Mattias et al. 1988;Bernoulli et al. 2004). The potentially great spatial extent of this layer and the possibility that the conditions analyzed here may occur in other similar settings makes it important to identify its presence earlier to prevent analogous situations.
<p>A physically based model for shallow landslide triggering (HIRESSS &#8211; HIgh REsolution Soil Stability Simulator) was applied in a 100 km<sup>2</sup> test site in Central Italy (Urbino, Marche region). The objectives were assessing &#160;the influence of additional cohesion provided by roots and testing the effectiveness of a geotechnical characterization performed in an another area, but on similar lithologies.</p><p>We performed two different simulations considering the rainfall event of January-February 2006, which triggered 14 landslides in the area. For both the simulations, rainfall data were fed into the model using the measurements at hourly time step of a nearby rain gauge station, while soil thickness was estimated using a state-of-the-art empirical model based on geomorphological parameters derived from curvature, slope gradient, lithology and relative position within the hillslope profile. Geotechnical input data were varied among the two simulations. In the first one, a few in-situ and laboratory tests were performed to characterize the main lithologies, while the remaining lithologies were characterized using literature data. In the second simulation, the main geotechnical and hydrological parameters (cohesion, internal friction angle, soil unit weight, hydraulic conductivity) were fed into the model using a geostatistical characterization performed on hundreds of measurements carried out in another Italian region, with similar lithologies. Furthermore, in the second simulation the additional cohesion provided by the plant roots was also taken into account.</p><p>The results obtained with the two simulations were validated considering the landslide dataset collected by field work and image interpretation shortly after the rainfall event studied. We discovered that the second simulation provided much more reliable results, with the areas surrounding the landslide locations characterized by much higher values of failure probability.</p><p>The outcome is very important to address future research in distributed slope stability modelling because it proved that: (i) additional root cohesion is an important factor that can be used to get more reliable results; (ii) when in need of characterizing the geotechnical parameters of the study area, instead of using just a few measurements performed therein, it is preferable to integrate also data coming from different areas but with similar lithologies if they were robustly characterized in geostatistical terms purposely for distributed slope stability studies.</p>
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