The Scascoli Gorge (25 km S of Bologna, Italy) has a structural predisposition to slope instability, which is made worse by a huge dormant landslide affecting the right valley-side (see Part 1). The NW cliff, and part of the SE cliff of the Gorge are often involved in rock falls from fractured and weathered sandstones. The number of events recorded in the last decades testifies a permanent danger for the road underneath. On October 15th, 2002 a rock volume of about 20000 mc fell from the NW cliff, obstructing the Savena riverbed and destroying a 150 m long road segment. At first, the hydrological emergency was faced by outflow race. Subsequently, blasting experts blew up potentially dangerous rock bridges. Eventually, after removal of the collapsed blocks, the road-path was re-established. In order to increase the road safety level, preliminary protection and consolidation works (rock-fall drapes and barriers) were realised. Engineering design of those works was forerun by geologic and geotechnical investigation of both valley-sides. Climbing geologists collected data about the structural fabric of the cliffs, and fracture orientation was analysed by stereographic plotting. This way several sites were recognized, where slope stability is severely impaired by potential rock failures (planar, wedge and toppling). Consequently, today the most critical discontinuities are being monitored by 33 surface extensometers. In addition, a geotechnical monitoring system (2 standpipe piezometers, 6 inclinometers, 1 weather station and other miscellaneous devices), and a topographic network (41 points) constantly control the overall slope stability of the Scascoli Gorge. Planning for the 2004 includes: new geotechnical investigations by stratigraphic boreholes and refraction seismic cross-sections, with tomography interpretation; implementation of automatic GSM data transmit for surface extensometers; installation of new inclinometers, standpipe piezometers and a multipoint borehole extensometer. In our opinion, the strong predisposition to slope instability of the Scascoli Gorge has to be faced by an alternative road-path layout, inclusive of tunnel and bridge designing. For this reason, remoulding of the most critical slopes by controlled blasting or rock excavation is also being evaluated. The use of GIS techniques and 3D modelling (displayed by computer rendering and interactive multimedia format) helps analysing different solutions for environmental restoration.
LANDSLIDES IN THE SCASCOLI GORGE (BOLOGNA APENNINES, ITALY): FROM RECONNAISSANCE TO MONITORING (PART 2)
LANDUZZI, ALBERTO;MARCHI, GIANFRANCO
2004
Abstract
The Scascoli Gorge (25 km S of Bologna, Italy) has a structural predisposition to slope instability, which is made worse by a huge dormant landslide affecting the right valley-side (see Part 1). The NW cliff, and part of the SE cliff of the Gorge are often involved in rock falls from fractured and weathered sandstones. The number of events recorded in the last decades testifies a permanent danger for the road underneath. On October 15th, 2002 a rock volume of about 20000 mc fell from the NW cliff, obstructing the Savena riverbed and destroying a 150 m long road segment. At first, the hydrological emergency was faced by outflow race. Subsequently, blasting experts blew up potentially dangerous rock bridges. Eventually, after removal of the collapsed blocks, the road-path was re-established. In order to increase the road safety level, preliminary protection and consolidation works (rock-fall drapes and barriers) were realised. Engineering design of those works was forerun by geologic and geotechnical investigation of both valley-sides. Climbing geologists collected data about the structural fabric of the cliffs, and fracture orientation was analysed by stereographic plotting. This way several sites were recognized, where slope stability is severely impaired by potential rock failures (planar, wedge and toppling). Consequently, today the most critical discontinuities are being monitored by 33 surface extensometers. In addition, a geotechnical monitoring system (2 standpipe piezometers, 6 inclinometers, 1 weather station and other miscellaneous devices), and a topographic network (41 points) constantly control the overall slope stability of the Scascoli Gorge. Planning for the 2004 includes: new geotechnical investigations by stratigraphic boreholes and refraction seismic cross-sections, with tomography interpretation; implementation of automatic GSM data transmit for surface extensometers; installation of new inclinometers, standpipe piezometers and a multipoint borehole extensometer. In our opinion, the strong predisposition to slope instability of the Scascoli Gorge has to be faced by an alternative road-path layout, inclusive of tunnel and bridge designing. For this reason, remoulding of the most critical slopes by controlled blasting or rock excavation is also being evaluated. The use of GIS techniques and 3D modelling (displayed by computer rendering and interactive multimedia format) helps analysing different solutions for environmental restoration.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
