Gallivaggio rock cliff: Risk management and reinforced earth embankment for rockfall protection
Zusammenfassung
The Gallivaggio landslide falls within the San Giacomo Filippo municipality (Sondrio) and affects a portion of slope situated in the lower Spluga Valley. The rock cliff overlooks the “Madonna di Gallivaggio” Sanctuary (17th century), a restaurant, a few houses and a section of the National Road no. 36 “del Lago di Como e dello Spluga” which leads to the tourist resort of Madesimo and to the Spluga Pass on the Swiss border. Hence the need for careful planning of control and design tools aimed at both risk management and risk mitigation. The first monitoring activities of the rock cliff date back to 2006, while in 2011 a survey activity with GBInSAR technology was started by the Geological Monitoring Centre of ARPA Lombardia (CMG). On 29th May 2018, a rock mass of about 5500–6000 m3 detached from the top of the rock cliff, completely filling up the existing catchment ditch behind the protection wall, demolishing part of the defence works and affecting the Sanctuary, the National Road and part of the other accommodation facilities situated at the foot of the rock face. This rockfall, as well as other minor recent falls, allowed to recognize the urgent need for a more adequate protection works. As a first step of a complex of works for the mitigation of the rockfall hazard, a new earth reinforced embankment was conceived. Both phases, designing and building, are described in the paper.
Ergebnis
Prior to the commencement of the work, it was necessary to secure the tunnel by laying netting on the upper part of the wall above, also in the event of new detachments after the project delivery. A total of 50,000 m2 of netting was laid on the upper part of the 450 m high wall. With the help of a Kamov helicopter, 300 m long and over four tonnes heavy nets were laid, making it Europe’s first and largest netting project on a rocky slope. At the end of the construction activities, a total of approx. 45,000 m3 of material was moved. Thanks to the screening and crushing activities, which were foreseen by the project and coordinated during the construction management phase, the new embankment was entirely built using all the material that collapsed in May 2018, all the material that made up the old embankment and part of the slope debris within the site area. The reinforced earth fill embankment is 243 m long and has an interception height varying
from 4 to 14 m while the height of the face on the downstream side varies from 7 to 23 m.