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

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 phenomena in the form of slow movements and failure events, which in turn have periodically caused 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 to understand the present complex evolution of the clayey slope. Finally, the strong ...

[1]  A. Parker,et al.  Geotechnical, mineralogical and chemical interrelationships in weathering profiles of an overconsolidated clay , 1979, Quarterly Journal of Engineering Geology.

[2]  R. Chandler,et al.  Lias clay: weathering processes and their effect on shear strength , 1972 .

[3]  J. Malet,et al.  Hydrological behaviour of earthflows developed in clay-shales: investigation, concept and modelling. , 2004 .

[4]  Alec Westley Skempton,et al.  STABILITY OF NATURAL SLOPES AND EMBANKMENT FOUNDATIONS , 1969 .

[5]  A. Skempton.  Long-Term Stability of Clay Slopes , 1964 .

[6]  A. Pasuto,et al.  A visco-plastic model for slope analysis applied to a mudslide in Cortina d'Ampezzo, Italy , 1996, Quarterly Journal of Engineering Geology.

[7]  K. Terzaghi,et al.  Soil mechanics in engineering practice , 1948 .

[8]  M. Sciotti,et al.  Problemi di stabilita della rupe di Orvieto , 1980 .

[9]  L. Picarelli,et al.  Remarks on the mechanics of slow active landslides and the interaction with man-made works , 2004 .

[10]  David M. Cruden,et al.  LANDSLIDES: INVESTIGATION AND MITIGATION. CHAPTER 3 - LANDSLIDE TYPES AND PROCESSES , 1996 .

[11]  J. N. Hutchinson.  A Coastal Mudflow on the London Clay Cliffs at Beltinge, North Kent , 1970 .

[12]  Jeffrey A. Coe,et al.  Seasonal movement of the Slumgullion landslide determined from Global Positioning System surveys and field instrumentation, July 1998–March 2002 , 2003 .

[13]  L. Bjerrum.  PROGRESSIVE FAILURE IN SLOPES OF OVERCONSOLIDATED PLASTIC CLAY AND CLAY SHALES , 1967 .