1. BENCH STRUCTURAL INTEGRITY
FOR OPTIMUM PERFORMANCE OF
CABLE SHOVELS
Eric Gbadam,
PhD Student, Department of Mining & Nuclear Engineering
Missouri S&T, Rolla, MO
Samuel Frimpong, PhD, PEng
Prof. & Chair, Department of Mining & Nuclear Engineering
Missouri S&T, Rolla, MO
September, 12 2013
2. PRESENTATION OUTLINE
Introduction
Objectives
Methodology
 Finite Element Model
Results and Discussions
Conclusions
Source: P&H, 2010
Source: Jacque & Riesland, 2013
3. INTRODCUTION
 Primary choice of equipment for oil sands
excavation
 The loads are transferred to formation
via the crawlers
 This cyclic loading reduces the oil sand
shear strength & causes instability (failure)
 Bench failure leads to lost in production
and increase in downtime
Source: Frimpong, 2012
4. INTRODCUTION Cont’d
 Load bearing capacity oil sands is low due
to bitumen (8% to 15%)
 Temperature changes during summer and
winter
 Average stress due to machine weight on
crawlers be smaller to prevent sinkage
 Shovel sinkage leads:
carbody and side frame cracks
associated increased downtime
Increased maintenance cost
Subsequent reduced availability
Source: Grondin, 2008
5. OBJECTIVES
 To develop 3D Finite Element (FE) model
shovel crawler-oil sands interactions using
ABAQUS
 To examine the average stresses and
deformations on the formation during
excavation
6. METHODOLOGY
The FE model were developed based on the principle of soil
mechanics by assuming that:
the oil sand is homogeneous, isotropic undergoing elasticplastic deformation;
the crawler tracks were treated as a rigid strip footing
resting on the oil sand; and
the pressure distribution underfoot the tracks were
uniform.
The oil sand formation was modeled as elastic-plastic
material with strain-softening Mohr-Coulomb criterion.
7. Shovel Crawler-Oil Sands Interactions
Table 1 Physical Dimensions of 3-D cable shovel crawler-oil sand model
L (m)
B (m)
H (m)
S (m)
W(m)
b (m)
h (m)
25
20
10
10.5
2.21
4.5
1
 Dimensions (Table 1) chosen to minimize
boundary effect on formation behavior
 Half symmetry model (Fig. 1) is used in the
simulation to reduce computational time
 Crawler track is modeled as a rigid
rectangular footing
 Contact interaction is modeled using
Coulomb friction criterion (eqn 1)
Fig. 1 3D half model
8. FE Model of Crawler-Oil Sands Interaction
Elastoplastic model of the oil sand under strain softening
Mohr-Coulomb’s failure (eqn. 2)
Table 2 gives the parameters used for the oil sand model
and simulation
ρ1
E1
ET1
T1
c2
Ψ2
(kg/m3)
(MPa)
(MPa)
(°C)
(kN/m2)
(°)
0.1
25
10
10
1600
0.1
10
0.3
Source: 1Li et al (2012) and 2Anochie-Boateng (2008)
30.67
9. FE Model of Crawler-Oil Sands Interaction
 Meshes under the tracks are
finer (Fig.2) to account for high
stress concentration zone
 The elements selcted for both
oil sand and tracks was C3D8R,
3D, 8-node linear brick
 This elements uses reduced
integration technique which
greatly reduces computation
time
Fig. 2 FE mesh and boundary condition for 3D
oil sand-crawler model
10. FE Model of Crawler-Oil Sands Interaction
 The base of the model is fixed in
all directions
 All vertical boundaries are fixed
in the perpendicular direction
but free in the vertical direction
 All nodes along the plane of
symmetry given ZSYMM
condition
Fig. 2 FE mesh and boundary condition for 3D
oil sand-crawler model
11. FE Model of Crawler-Oil Sands Interaction
Terzaghi’s classical bearing capacity equation forms the
foundation for this model
Overburden pressure used to account for depth of
influence
12. FE Model of Crawler-Oil Sands Interaction
The loads are applied very slowly to avoid exciting the
model
Gravity and surcharge loads are applied to initiate the
induced stresses
13. FE Model of Oil Sands Deformation
(a)
(b)
(d)
(c)
Fig. 3 Deformation contour plot of oil sand-crawler interface, (a) 3-D isometric view showing
maximum deformation (b) Deformation under the tracks (c) deformation along the symmetry
plane in 2-D and (d) Top view of oil sand deformation
14. FE Model of Oil Sands Deformation
 Deformation of the oil sand occurs underfoot the tracks and
spreads laterally to the surface of the oil sand (Fig 3a), the
maximum deformation of 2.497 cm under the tracks.
 The deformation increases nonlinearly from the top surface to the
(a)
bottom of the formation as shown in Fig. 3(c).
(b)
 The top view (Fig. 3(d)) presents deformation spreading concentric
with maximum occurring at the edges of the track and beyond.
 Vertical displacement of the oil sand below the track is shown
plotted in Fig.4 at a time of 0.13 seconds.
(c)
15. FE Model of Oil Sands Deformation
 This figure depicts nonlinearly behavior of the formation under
static loads
Fig. 4 Displacement-time graph of oil sand-track interface
16. FE Model of Oil Sands Deformation
(a)
Fig. 4 Zones of elastic and
plastic strain at failure for oil
sand,
(a) maximum principal elastic
strain, (b) 2-D elastic strain and
(c) plastic strain
(b)
(c)
17. CONCLUSIONS
The following conclusions are made based on the FE
simulation results from ABAQUS:
 FE analysis has been implemented successful to fully
produce 3-D oil sand-track interaction that reasonably
predicts formation response to a static load.
 Three distinct oil sand regions were observed from the
plastic strain failure pattern: the region below the tracks
recording larger strain at failure, region adjacent the tracks
and expanding dipper and wider in all directions.
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