A Retrospective on LaModel
or
Dr. Heasley’s Wild Ride
It doesn’t look
so bad with
my eyes
closed
Dr. Keith A. Heasley
Professor
Department of Mining Engineering
West Virginia University
Keith.Heasley@mail.wvu.edu
(304) 293-3842
A Retrospective on
LaModel
Development
Application
Enhancement
MULSIM
NIOSH
Boundary Element Program for
Displacement and Stress Analysis
in Coal Mines
Boundary-Element
Displacement Discontinuity Method
D is p la c e m e n t D is c o n tin u ity A p p ro x im a tio n
1
M in e d P a n e l
2
3
E le m e n t
4
5
6
S o lid C o a l
Homogeneous Overburden
Ground Surface
H
z
P
Coal Seam
Longwall Panel Convergence
Convergence (m)
0.00
Homogeneous Elastic Overburden
0.10
C
L
L
0.20
M
100
0
0.30
0.40
Laminated (t=15) Overburden
0.50
0
20
40
60
80
Distance from Center of Panel (m)
100
Surface Subsidence (m)
Surface Subsidence
0.0
Homogeneous Elastic Overburden
-0.5
H
-1.0
Laminated (t=5.3)
Overburden
C
L
-1.5
Empirical
Subsidence Curve
L
M
-200
-100
0
100
Distance from Center of Panel (m)
200
Laminated Overburden
Ground Surface
0
H
1
z
P
j-1
j
tj
E j
vj
j+1
n-1
n
n+1
Coal Seam
Longwall Panel Convergence
Convergence (m)
0.00
Homogeneous Elastic Overburden
0.10
C
L
L
0.20
M
100
0
0.30
0.40
Laminated (t=15) Overburden
0.50
0
20
40
60
80
Distance from Center of Panel (m)
100
Surface Subsidence (m)
Surface Subsidence
0.0
Homogeneous Elastic Overburden
-0.5
H
-1.0
Laminated (t=5.3)
Overburden
C
L
-1.5
Empirical
Subsidence Curve
L
M
-200
-100
0
100
Distance from Center of Panel (m)
200
LaModel
Laminated
Boundary Element Program for
Displacement and Stress Analysis
in Coal Mines
LaModel
Uses a Laminated Overburden Model
More Realistic Stresses and Displacements
Used to Model:
Multiple Seams
Variable Topography
Complex Mining Geometries
etc.
Case Study
Case Study
Upper Mine:
Room-and-Pillar
Overburden – 500 to 1300 ft (855 ft)
Seam Thickness – 5.0 ft
7 Entry Rooms, Retreated
Lower Mine:
Room-and-Pillar
Interburden 45 ft
Seam Thickness - 5.0 ft
7 Entries – 60 by 70 ft Pillars
Overburden Stress
Single Seam Stress
Multiple Seam Stress
Total Vertical Stress
Stress Hazard Map
Gob
Gob
Basic Features
Displacement and Stress Calculations
Multiple Seams
Multiple Mining Steps
26 Different Seam Materials
6 Non-Linear Seam Models
Material Models
1
Linear Elastic
2
Strain Softening
3
Elastic Plastic
4
Bi-Linear Hardening
5
Strain-Hardening
6
Linear Elastic Gob
LaModel Enhancements
Graphical Post-Processing (1996)
Graphical Grid Generation (1999)
Coal Wizard (2000)
Grid Size Increases
Pillar Safety Factors (2006)
Lam2D (2003)
Stability Mapping (2006)
LamPlt
Grid Editor
Grid Size
Grid Size
250 x 250 (1996)
400 x 400 (2000)
1000 x 1000 (2004)
2000 X 2000 (2010)
Keith;
I need bigger
grids, and
more seams
Grid Generator
Grid Generator
Pillar Safety Factor
Energy Calculations
Lam2D
Keith:
2D is the way
to go.
Stability Mapping
Crandall Canyon
Mine Collapse
Final Model
Final Model
LaModel Calibration
 Developed a procedure that calibrated:
 The Rock Mass Stiffness against the
extent of the abutment zone
 The Gob Stiffness against the
expected gob loading (21° abutment
angle)
 The Coal Strength with empirically
determined pillar strength (900 psi).
Thickness Wizard
Calibrated Database
2.50
LaModel Safety Factor
2.25
2.00
1.75
Design Line
1.50
1.25
1.00
Even Split
Failures
0.75
Middling
0.50
Success
0.25
0.00
600
800
1000
1200
1400
Depth (ft)
1600
1800
2000
2200
Calibration Results
 Calibrated Safety Factor:
 Keep the Safety Factor > 1.4 and
 < 10% chance of failure
Future Developments
 Calibrate to “shallow cover”
 Re-examine Abutment Extent
 Local Mine Stiffness Calculation
 ARMPS-LAM
 Improve the speed of the MultipleSeam calculation
ARMPS-LAM
Incorporate a
laminated
overburden loading
model into the
ARMPS program
Keith:
You should build
the laminated
model into ARMPS
Future Developments
 Calibrate to “shallow cover”
 Re-examine Abutment Extent
 Local Mine Stiffness Calculation
 ARMPS-LAM
 Improve the speed of the MultipleSeam calculation
Dr. Heasley’s Wild Ride
Where to next?
Questions?
Maybe, if I
close my
eyes, I won’t
have to ask
questions
Boundary-Element
Displacement Discontinuity Method
Boundary-Element
Displacement Discontinuity Method
Boundary-Element
Displacement Discontinuity Method
Boundary-Element
Displacement Discontinuity Method