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Figure 3. Preparation of the ping-pongball experiment.
powdersnowavalancheswhichrundownforafew
kilometerdistance.
In the experiments, 300,000 balls at the maximum were
stored in a large container set on top of the landing-bahn
(landingpath).Experimentpreparationareshown
schematically in Figure 3.Ping-pong balls were released
simultaneouslywithopeningthe frontgateofthecon-
tainer.Then the flowaccelerated down onthe inclined
plane which is more than 150m long and 30 m wide. The
floor was made with the artificial lawn and its inclination
amounted to 36 deg.from K to P point in Figure 1.After
passing thesteepestpart, theflow deceleratedandstopped
on the braking track.Individual movements of the balls
and flow behaviors were recordedwith several video cam-
eras. In addition, upon coming to rest, the debris distribu-
tion was measured as a function of position.Four towers
were set 10 mdown from the K-point toinvestigate the
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structures of these three dimensional granular flows.The
tower structures andmeasuringdevicesmountedon it were
almost as same as those used in the snow flow experiments
except the height of towerwas 60 cm.
RESULTS AND DISCUSSIONS
Snow flow experiments
Each experimental run was recorded with several sets of
video cameras.Analysis of pictures are utilized to obtain
the position of the leadingedge(front) as afunction of time.
As shown in Figure 4 the snow flow increasedthe velocity
linearlywithdistanceandreachedabout12m/safter
flowingdown35mfromthe starting point.Asthe flow
reachedabout 7 m/s, a powder cloud was observed to form
andobscuredthe denserflow(Figure5).Afterwards,it
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