Boundary Element Displacement-Discontinuity Modeling. LaModel 21&30

Transcription

1 Boundary Element Displacement-Discontinuity Modeling LaModel 21& Dr. Keith A. Heasley Professor Department of Mining Engineering West Virginia University (304)

2 Keith A. Heasley Biography B.S. Mining Engineering Penn State 1981 Consolidation Coal Co. Project Engineer M.S. Mining Engineering Penn State Thesis - Computer Modeling of Subsidence U.S. Bureau of Mines/NIOSH Ph.D. Mining Engineering CSM 1998 Thesis DDM Modeling LaModel West Virginia University Present

3 Schedule Load Software and Files (0.50 hr) Introduce LaModel (0.50 hr) Instant Gratification (1.00 hr) Run Tutorial 1 Automatic Grid Generation (2.00 hr) Generate Mine Grid for Huff Creek Generate Overburden Grid Huff Creek Analyze Huff Creek Mine

4 Schedule (cont d) Calibration Calibrate Overview (0.75 hr) Calibrate Tutorial 1 (0.75 hr) LamPre3.0 (0.50 hr) Gory Details Derivation, Analytical Solutions, Influence Functions, Topography, Coal Strength, FAQs

5 Schedule (cont d) Gory Details LaModel Derivation (0.75 hr) Analytical Solutions (0.50) Influence Functions (0.50) Stability Mapping (0.75 hr) Examples (0.75 hr) Crandall Canyon Harris 23 Left

6 LaModel A Displacement-Discontinuity Variation of the Boundary-Element Method For Calculating Stresses and Displacements in Thin Bedded Deposits Coal, Salt, Potash, Limestone, etc.

7 LaModel Uses a Laminated Overburden Model More Realistic Stresses and Displacements Used to Model: Multiple Seams Complex Mining Geometries Yielding Pillars Variable Topography etc.

8 Multiple Seam Stress Gob Lower Mine Legend (MPa) Gob Upper Mine

9 LaModel LaModel System Uses Three Programs LamPre Pre-processor for developing an input file LaModel Number Cruncher LamPlt Post-processor for graphing and plotting results

10 History LaModel Number Cruncher Originally written in 1994 DOS-Based, C 250 x 250 grid

11 History LamPlt Graphical Post Processor Originally written in 1996 Windows Based, Visual C++ Colored Square Plots Cross-Sections

12 Colored Square Plot

13 Cross Section Plot

14 History LamPre Forms-Based Parameter Input Graphical Grid Generation Originally written in 1998 Windows Based, Visual Basic

15 LaModel Grid Editor Interface

16 History 1999 LaModel implemented in Visual C++ Posted t d on NIOSH WebSite 2000 Coal and Gob Wizard added 400 x 400 Grid

17 History 2001 Automatic Mine Grid Generation added Automatic Topo Grid Generation added 2002 Units carried through the calculation History and Fishnet Plots added

18 History 2003 LaM2D Created 2004 Grid Generation coded directly into AutoCAD 1000 x 1000 Grid Pillar Safety Factors added Intra-Seam Subsidence added

19 History 2006 Stability Mapping Program created Incorporating LaModel with Geology and Structural Features into a Comprehensive Stability Mapping System

20 History 2007 LaM2D coded into AMSS program. The Two Dimensional Multiple-Seam Stress from LaM2D is used to Add a Multiple-Seam Capability to ALPS and ARMPS.

21 History 2007 Crandall Canyon Mine Collapse Highlighted a need for: Better (Standardized) Calibration Techniques Verified Calibration Techniques Better Documentation of the Program and Calibration

22 Present LaModel3.0 Rock Mass Stiffness Wizard Gob Load Wizard Pillar Strength Wizard Energy Release Calculations Strain Softening Material Wizard Local Mine Stiffness Calculation Fault Model Roof Bending Stress Calculation

23 Energy Calculations Energy Released During the Bump Cut

24 Present : LaModel X 2000 Grid Size Improved Mine Grid Generator Specify Coal and Gob Material Codes Improved Coal Wizard Improved Grid Editor Change All, Undo, Tracking Window LamPlt - Zoom Training Manual

25 Numerical Stress Analysis Numerical Modeling - Mathematical approximation of the geo-mechanical behavior of the coal and overburden, based on the fundamental laws of physics. In contrast to Empirical Design - Mathematical design equations based primarily on measured or observed behavior.

26 Numerical Stress Analysis Based on The Fundamental Laws of Physics: Theory of Elasticity Stress Equilibrium

27 Numerical Stress Analysis Strengths: Analyze complicated geometry and material behavior; multiple-seams, floor heave, cutter roof, roof bolt behavior. Can go beyond previous experience Good for relative comparisons

28 Numerical Stress Analysis Weaknesses: Natural geologic material does not follow theoretical behavior; It is inhomogeneous, non-isotropic, inelastic and varies through distance. Models require complex, difficult-to-obtain input information. Models must be calibrated with reality.

29 Numerical Stress Analysis Four Major Methods: Finite-Element. Finite-Difference Discrete Element Boundary-Element

30 Boundary Element Method Discretizes the Boundary of the Continuum Computationally Efficient Particularly Suited for Large Areas of Tabular Seams or a Few Large 3-D Openings BSOLV, MULSIM, MINLAY, LAMODEL

31 Finite-Element Vs. Boundary-Element

32 Boundary-Element Displacement Discontinuity Method Displacement Discontinuity Approximation Mined Panel Element Solid Coal

33 Laminated Model Fundamental Equation Where:

34 NIOSH Boundary-Element Codes MULSIM and LAMODEL Boundary Element Programs for Displacement and Stress Analysis in Coal Mines

35 NIOSH Boundary-Element Codes MULSIM - Homogeneous Elastic Overburden (one solid material) LAMODEL - Laminated Overburden (frictionless homogeneous laminations)

36 Homogeneous Overburden Ground Surface z P H Coal Seam

37 NIOSH Boundary-Element Codes MULSIM - Homogeneous Elastic Overburden (one solid material) LAMODEL - Laminated Overburden (frictionless homogeneous laminations)

38 Laminated Overburden Ground Surface 0 1 j-1 z P H j t j E j v j j+1 n-1 n n+1 Coal Seam

39 Longwall Panel Convergence 0.00 Homogeneous Elastic Overburden Convergen nce (m) C L L M 0.50 Laminated (t=15) Overburden Distance from Center of Panel (m)

40 Surface Subsidence Surface Subsid dence (m) 0.0 Homogeneous Elastic Overburden Laminated (t=5.3) Overburden -1.5 LC Empirical Subsidence Curve Distance from Center of Panel (m) L H M

41 So what is involved in modeling a mine plan with LaModel

42 Modeling a Mine Plan Mine Layout Mine Grid Schematic Coarse Mesh Fine Mesh Boundary Fine Mesh

43 Modeling a Mine Plan Gob Area Area of Interest Pillar Section 1. Pick the Area of Interest

44 Modeling a Mine Plan Fine Mesh Area 2. Determine the Mesh Area

45 Modeling a Mine Plan 3. Layout the Detailed Mesh

46 Modeling a Mine Plan EEEEE E E E E E E EEEEE E E E E E EEEEE E E E E EEEEE E E E E E E EEEEE E E E E E E CCCCCC C DDDD CC C D DD C D AAA A C C D A A D C EEEEE E E E E EE E E E E E E E CCCCCC 1 1 E EEEEE E E E E E E C DDDD CC C D DD C D AAA 1 1 E EEEEE E E E E E E A C C D A A D C 11CDDDDC 1 11CDDDDC E EEEEE E E E E E E 1 1 E E E E E E E EE E EE E EE E EE E E E E E E E E 1 1 C C C C C 1 1 C C C C C C CCCCCC CDDDDC C D D C 11CD A A 1 1 C DAA AA CDDDD DD CCCCCC CCC C E E E E E E E E CCCCCC 1 1 C DDDD CC C D DD C D AAA A C C D A A D C 11CDDDDC C C C C C C CCCCCC C DDDD CC C D DD C D AAA A C C D A A D C 11CDDDDC C C C C C C Determine the Material Codes

47 LaModel Grid Editor Interface

48 LaModel Input Overall Project Parameters Rock Mass Properties In Seam Material Properties Grid Geometry Program Control Parameters

49 Minimum Input Mine Map Geometry Mine Parameters Thickness, Depth Sense of Modeling Critical Area

50 Run the Input File

51 LaModel Output Seam Convergence Seam Stress Topographic Stress Multiple-Seams Stress Pillar Safety Factors Intra-Seam Subsidence & Strains Subsidence

52 LaModel Output Colored Square Plots Cross-Sections S History Plots Fishnet Plots

53 Colored Square Plot

54 Cross Section Plot

55 Numerical Stress Analysis Vs. Empirical Stress Analysis If your mining plan fits a scenario from ALPS, ARMPS, or AMSS then certainly use these empirical programs, and that may be all you need. However, if there is some "complication (complex geometry, variable topography, etc.), you may want to analyze your mining plan with a numerical model.

56 Questions?

57

58 Displacement Contours Distance above Seam (m) Horiz. Dist from Center of Seam Element (m) Laminated (t=15) Overburden Homogeneous Elastic Overburden Laminated (t=28) Overburden 0 M

59 Colored Square Plot SCALE

60 Cross Section Plot 3500 Total Value Plot of Stress Z Stress Z Distance along cross-section

61 Remote Displacement Displ. (m) Displ. (m) Homogeneous Elastic Overburden 50 m above seam Laminated (t=15) Overburden Horiz. Dist. from Center of Seam Element (m) Homogeneous Elastic Overburden 20 m above seam Laminated (t=15) Overburden M

62 Material Models Linear Elastic 2 Elastic Plastic 4 Strain-Hardening 6 Strain Softening Bi-Linear Hardening Linear Elastic Gob