The medieval town of Orvieto is built on the top of a pyroclastic slab overlying a gentle slope of overconsolidated clays. The clayey slope has been constantly affected by landslide phenomenona in the form of slow movements and failure events, which in turn have periodically caused the instability of the marginal areas of the pyroclastic slab. Since 1982 a number of Casagrande-type piezometers and inclinometers were installed in the northern slope of the Orvieto hill within the area that was involved in the huge Porta Cassia landslide in 1900. In this paper, after a brief description of the geology and the geotechnical properties of the slope, data obtained through the monitoring system are illustrated. Piezometric data are utilized to develop a conceptual model of the hydraulic conditions in the clayey slope and inclinometer measurements are interpreted and correlated with the geotechnical ground profile and slope morphology in order to understand the present complex evolution of the clayey slope. Finally, the strong correlation between the rainfall regime, the piezometric levels and the rate of movements is discussed and the recurrence periods of critical cumulative rainfall on displacement trends are estimated on the basis of statistical methods.

Influence of rainfall regime on hydraulic conditions and movement rates in the overconsolidated clayey slope of the Orvieto hill (Central Italy)

BOLDINI, DANIELA;
2006

Abstract

The medieval town of Orvieto is built on the top of a pyroclastic slab overlying a gentle slope of overconsolidated clays. The clayey slope has been constantly affected by landslide phenomenona in the form of slow movements and failure events, which in turn have periodically caused the instability of the marginal areas of the pyroclastic slab. Since 1982 a number of Casagrande-type piezometers and inclinometers were installed in the northern slope of the Orvieto hill within the area that was involved in the huge Porta Cassia landslide in 1900. In this paper, after a brief description of the geology and the geotechnical properties of the slope, data obtained through the monitoring system are illustrated. Piezometric data are utilized to develop a conceptual model of the hydraulic conditions in the clayey slope and inclinometer measurements are interpreted and correlated with the geotechnical ground profile and slope morphology in order to understand the present complex evolution of the clayey slope. Finally, the strong correlation between the rainfall regime, the piezometric levels and the rate of movements is discussed and the recurrence periods of critical cumulative rainfall on displacement trends are estimated on the basis of statistical methods.
P. Tommasi; P. Pellegrini; D. Boldini; R. Ribacchi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/15926
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