A Model for Rockfall Test

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A Model for Rockfall Test
?Artificial rock model for rockfall test Five
iron balls (diameter 11mm, weight 5.48g) are
connected by adhesive.
The model is easily simulated by DEM
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Experiment Condition
Slope (Wood)
Magnetic switch
rock
?
Height 30cm
100cm
? front
50cm
30 degree
Initial Direction
ltside viewgt
Set the rock model to same direction, then drop
it by magnet switch in order to drop the rock
model in same condition
From slope foot, Y
drop
From center, X
ltplane viewgt
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Distribution of distance
We repeat the experiment 300 times (drop of the
rock model)
X-direction (from center) Mean µx 0.4cm
St.Dev. 19.2cm Y-direction (from foot) Mean
µY 68.0cm St.Dev.sY24.2cm
X
Center line
Y
slope foot
From slope foot, Y (cm)
slope
drop
slope top
ltplane viewgt
From center, X (cm)
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Numerical Simulation by DEM
?Input parameter
?DEM model
?up
Spring constant (normal, shear) 2.40105
N/m Damping constant (normal) 4.54101
Ns/m Damping constant (shear) 5.80101
Ns/m Friction angle between slope and
particles 24.7 degree They are determined
from simple test (rebound height), and material
property.
?front
All conditions, such as initial position, height
of drop, etc., are same as the experiment
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Perturbation of initial position in DEM
Rotate the model around axis X, Y, Z with
uniform random number Case 1 -1 to 1, Case 2
-3 to 3, Case 3 -5 to 5 (degree)
An example of DEM result Trajectory of the rock
model
Magnetic switch
?
X in plane view
From center, X (cm)
Side view
Height (cm)
? front
Horizontal location (cm)
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Comparison of Experiment and DEM
Rotate the model around axis X, Y, Z, with
uniform random number Case 1 -1 to 1 degree
Experiment DEM
From slope foot, Y (cm)
From center, X (cm)
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Comparison of Experiment and DEM
Rotate the model around axis with uniform random
number Case 1 -1 to 1, Case 2 -3 to 3, Case
3 -5 to 5 (degree)
Cumulative curves are almost same irrespective
of case 1-3 (uncertainty of position) Output
uncertainty does not depends on input
uncertainty
From center, X
From slope foot, Y
Cumulative Distribution
DEM, Case 1 DEM, Case 2 DEM, Case 3 Experiment
From center, X (cm) or From slope foot, Y (cm)
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DEM result by Compiler A and B
Highly nonlinear simulation is sensitive to small
change of any condition. What happens when the
compiler is changed? All conditions are same
except the COMPILER!
Case 1 -1 to 1 (degree)
Compiler A Compiler B
Plane View
Side view
From center, X (cm)
Height (cm)
From slope foot, Y (cm)
Compiler A Compiler B
Horizontal location (cm)
From center, X (cm)
Treatment of last digit of significant figures
depends on compiler, option.
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DEM result by Compiler A and B
Rotate the model around axis X, Y, Z, with
uniform random number Case 1 -1 to 1 (degree)
From center, X
From slope foot, Y
Cumulative Distribution
Compiler A Compiler B Experiment
From center, X (cm) or From slope foot,
Y (cm)
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Concluding Remarks

• Rockfall test
• The places where the rock model stop have large
  uncertainty
• Simulations of the rockfall test by DEM
• Good agreement in terms of distributions of the
  place where the model stop
• Uncertainty level of initial condition does not
  affect the distribution
• A compiler of DEM program affect each simulation,
  but does not affect the distribution

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