1. A simple guide to BESOL_MS Including a review of the shaft pillar modelling done at Frank 1 shaft June 2005 Written an presented by GS Potgieter

2. This presentation is to assist people who have never modelled with BESOL or have not used the package in a long time. This is a walk trough the features used in the review of the shaft pillar

3. The program consists of three parts

4. MSPREP Parameters Digitization Griddling Sequencing mining steps Positioning windows

5. The program consists of three parts MSPREP Parameters Digitization Griddling Sequencing mining steps Positioning windows MSCALC Running the model

6. The program consists of three parts MSPREP Parameters Digitization Griddling Sequencing mining steps Positioning windows MSCALC Running the model MSPOST Viewing the results

7. Before you start 1.Have a very good idea of what you want to get from the model 2.Understand this is a purely elastic model and the limits that imposes. 3.Prepare your plans you will need 6 points 3 X/Y, and 3 Z (on reef) with coordinate values for each reef horizon you will be including in you model. 4.Obtain poisons ratio for the rock you will be modelling. 5.Young's modulus of the rock you will be modelling. 6.The average density of the over burden. 7.The virgin stress regime of the area you want to model. 8.Your Codes of Practice should contain most of this information.

10. Digitization If your PC is not connected to a digitizer you will stop here

13. Digitizing golden rules

14. Save often

15. Digitizing golden rules Save often Close your lines

16. Digitizing golden rules Save often Close your lines 1-0-2-0-0

17. Gridding

20. You have 450 rows to divide amongst your seams

21. Select your seam and position your grid

22. MAP

23. Fill in the mining steps

24. Windows

26. Drag on reef window to position

27. Drag off reef window to position

28. Window can be rotated to vertical for shaft simulation

29. Parameters

37. Write input data files

40. EXIT AND RUN MSCALC If your PC is not connected to a BESOL Dongle you will stop here

41. Run A, then B, then C, then D, as required.

42. EXIT AND RUN MSPOST

45. White background is good for printed results

46. Example The author was requested by Management to investigate the possibility of mining two blocks of ground west of the Merensky Shaft Pillar. The blocks indicated in the 1 st and 2 nd figures below were identified as easily accessible, mine able ground positioned close to the shaft infrastructure. The current condition of the shaft was confirmed by the Author by accompanying of Engineering personnel during a weekly shaft inspection. The mining of the identified blocks of ground was then simulated in a single mining step to give a before and after comparison. This was done to investigate what effect such mining would have on the Main Shaft.

47. Young’s modulus-50 GPa Shear modulus-29 GPa Poison’s ratio -0.2 K - ratio-1.5 Stoping width-1.1 m for the Merensky reef -1.8 m for the UG2 reef Grid size-180 columns and 255 rows Element width-5.0 m Merensky – UG2 middling-133.5 m Mining steps used-2 (as is and with planned pillars totally extracted) ρ -2950 kg/m3 is used throughout

48. Blocks of ground selected due to ease of access Shaft

49. Simulated removal of blocks Shaft

50. Merensky seam grid 225 x 180 x 5

51. UG2 seam grid 225 x 180 x 5

52. Vertical window placed in shaft position

53. On reef windows placed at shaft position

54. SHAFT NOT MINED

66. ASPECTTOLERABLE LIMITSMODELLING RESULTS Absolute value of induced vertical strain.Less than 0.4 millistrains for the host rock and steelwork. The highest modelled values were 0.1 milli- strains for the Main shaft, in the vicinity of the Merensky reef intersection at mining step 2. This value is within the required parameters. Induced vertical stress in the shaft host rock.Equal to or below 18 MPa.The modelled stresses next to the shaft through the reefs are: 26.05 MPa at the Merensky reef 28.87 MPa at the UG2 reef. Virgin stresses at these points are 16.71 MPa and 20.57 MPa respectively. The induced stresses next to the shaft therefore are 9.34 MPa for Merensky and 8.3 MPa for UG2 reef at mining step 2. These values are below the required parameter. Strain in shaft lining.Equal to or below 2 millistrains.A maximum value of 0.1 milli-strains was modelled at mining step 2, which is within the required parameter. Total vertical stress in areas where service excavations are to be sited. Should not exceed half the Uniaxial Compressive Strength of the rock. UCS Merensky - 63.5 MPa UCS UG2 - 63 MPa The total vertical stresses modelled at mining step 2 are 26.05 MPa and 28.87 MPa for Merensky and UG2 reef horizons respectively and are within the required envelope.

67. AQPBGSP Thank you. Questions?