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“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.
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“Debris Flow Risk mitigation by the means of rigid and flexible barriers. Experimental tests and impact analysis” Anna Maria Ferrero, Luigi Canelli UniversitàdegliStudidi Parma Giuseppe Mandrone UniversitàdegliStudidi Torino Rif. Progetto ICE D.R. 975 del 26/11/2009
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. Experimentaltests Full scale tests NumericalModelling Understandproperly the interaction ofDebrisFlowswithbarriers and define a solid and easy touse design method Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209
EXPERIMENTAL METHOD Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209
EXPERIMENTAL METHOD Flows of water saturated sand Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209
BARRIERS INSTALLED Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209
DATA ANALYSES AND FIRST RESULTS Test analyses were conducted measuring: Flow depth at each level trasducers Dynamic Thrust using load cells …estimating: Flow velocity (using image analysis and level trasducers) 2. Froude number of the front 3. Adimensional impact force 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: 2. Hungr (1984): 3. Campania Region (After Sarno, 1998), Japan 4. Armanini & Scotton (1993): 1. Momentum balance: (vertical jet-like wave) Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209
Rigid barrier perpendicular to the channel Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209
Rigid barrier in vertical position 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) Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209
Rigid filter barrier in vertical position Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209
Net barrier vertical position 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. Filter and flexible barrier do not cause this phenomenon. 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. Real scale tests will be performed on a flexible net. 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 Università degli Studi di Parma Progetto ICE D.R. 975 del 26/11/2209