1. “Debris Flow Risk mitigation by the means of rigid and flexible barriers. Experimental tests and impact analysis” Anna Maria Ferrero, Luigi Canelli Università degli Studi di Parma Giuseppe Mandrone Università degli Studi di Torino Rif. Progetto ICE D.R. 975 del 26/11/2009

2. Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209 OUTLINE Rationale and objectives of the research Method (Laboratory Tests) First Results Concluding remarks and future developements

3. Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209 RATIONALE AND OBJECTIVES Despite there is no connection between debris flows frequency and global warming in the Alps, recent studies have concluded that debris flows are significantly increasing at the margin of glaciers (Chiarle et al. 2006) These events are among the largest in Italian Alps. Recently in order to control and mitigate debris and mud flows events, flexible barriers (such as net barriers) have been used. Noteworthy are the similarities between these barriers and the protections used for rock fall events. (Ferrero et al. 2010, Wendeler et al. 2008) For this typology of barriers there is no specific regulation, experimental results on debris flows impact on structures are controversial. Experimental tests Full scale tests Numerical Modelling Understand properly the interaction of Debris Flows with barriers and define a solid and easy to use design method

4. Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209 EXPERIMENTAL METHOD

5. Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209 EXPERIMENTAL METHOD Flows of water saturated sand Properties of the mixture d 50 (m) 0.001 Ф g (°)30 ρ s (kg/m 3 )2550 ρ f (kg/m 3 )1000 ρ m (kg/m 3 )1930 υsυs 0.6 υfυf 0.4 h f (m)0.02÷0.1 v (m/s)1.8÷5.5

6. Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209 BARRIERS INSTALLED

7. Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209 DATA ANALYSES AND FIRST RESULTS Test analyses were conducted measuring: 1.Flow depth at each level trasducers 2.Dynamic Thrust using load cells …estimating: 1.Flow velocity (using image analysis and level trasducers) 3.Adimensional impact force 2.Froude number of the front

8. Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209 DATA ANALYSES AND FIRST RESULTS and comparing the obtained value of the adimensional impact force with the following formulations: 1. Momentum balance: (vertical jet-like wave) 2. Hungr (1984): 3. Campania Region (After Sarno, 1998), Japan 4. Armanini & Scotton (1993): Adimensional Formulation 1. 2. 3. 4.

9. Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209 Rigid barrier perpendicular to the channel

10. Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209 Rigid barrier in vertical position

11. Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209 Dynamic thrust loading due to the impact of the peak of the sourge (duration 2/10 s) Impulsive load caused by the fall of the reflected wave into the channel (1/40 s)

12. Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209 Rigid filter barrier in vertical position

13. Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209 Net barrier vertical position

14. Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209 CONCLUDING REMARKS & FUTURE DEVELOPMENTS Results have shown that even if empirical, Hungr’s formulation (1984) is a solid and easy to use method for the estimation of the dynamic thrust of a debris flow. For channelized flows it has to be taken into account the possibility of an impulsive force due to the impact of the reflected wave into the channel. More tests will be conducted, changing the characteristics of the mixture and trying to evaluate the additional load due to collisional force of a single boulder. Filter and flexible barrier do not cause this phenomenon. Real scale tests will be performed on a flexible net.

15. Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209 Thank you for your attention! Contacts: luigi.canelli@nemo.unipr.it annamaria.ferrero@unipr.it