Bradley DarlingtonGround Support Engineer

Sandvik

Sandvik MD Bolt and In-situ Dynamic Testing of Ground Support

Sandvik MD Bolt and In-situ dynamic testing of ground support1

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• The Sandvik Mechanical Dynamic (MD) Bolt• History – design & development

• Bolt description, Installation and static performance

Sandvik MD Bolt and In-situ dynamic testing of ground support4

Outline

• In-Situ Dynamic testing• History

• Requirements of an in-situ test rig

• 1st trial concept and testing

• Alterations required to design

• Final rig design and testing

• Future plans

• Design• Single pass Mechanical bolt

• Suitable for seismic conditions

• Comprises of Friction shell and point anchor at toe end

• Development• Developed for ground conditions where standard friction bolts are not sufficient and resin/grouted

bolts are difficult to install.

• Developed in partnership with Fosterville gold mine in Bendigo, Victoria, Australia

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HistoryThe Sandvik MD Bolt

• Installation• Installed with Jumbo in Australian mines.

• Installed with same procedure as a traditional friction bolt, with additional rotation process.

• Usage• Major usage at 6 sites across Australia.

• 10 additional site in trial phase.

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Installation/UsageThe Sandvik MD Bolt

• Testing• Standard QC testing involves in-situ quasi-static pull testing.

• Non-destructive testing to 15t.

• Typically 1% of installed bolts.

• Site feedback• Simple 1 pass bolt.

• Operator acceptance.

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The Sandvik MD Bolt

• Lab testing• Test laboratories include WASM (Australia), CANMET (Canada)

• Performed under laboratory conditions.

• Difficult to correlate to underground rock conditions.

• Loading is purely axial.

• Current “in-situ” testing (underground)• Installation QC test has been used at 1 site in Australia, but did not allow

measuring of load, and was very basic.

• Proved effective for QC testing.

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HistoryIn-Situ Dynamic testing

• Development• Initial concept developed in partnership with Mt Charlotte mine

(KCGM)

• Hybrid of existing test rig and Sandvik design

• All design completed, and verified through the use of Finite Element Analysis (FEA).

• KCGM (Kalgoorlie Consolidated gold mine) testing• 3 bolt tested, with total of 6 drops

• Input energy estimated at 15kJ.

Sandvik MD Bolt and In-situ dynamic testing of ground support9

1st trial concept and testingIn-Situ Dynamic testing

Plate to transfer load to bolt

Chain assembly (2.15m drop height)

890kg Mass (mill balls and shot-crete)

Sandvik claws to couple load plate to bolt

Hybrid test rig

• Modifications from the trial design• Release mechanism requires review.

• Load transfer element should not be chains.

• Energy application method needs to be adjustable, up to 30kJ.

• Load/energy applied to bolt must be measured.

• Displacement can be measured more effectively.

• Time to assemble (both on new bolt or on same bolt) must be reduced.

• Method to remotely release and to record load and displacement.

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Final rig designIn-Situ Dynamic testing

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Testing and resultsIn-Situ Dynamic testing

•First site trial of final rig • Conducted at Mine A in Tasmania, Australia.

• 5 Bolts tested with a total of 6 drops

• The impact energy was varied between 17-33kJ, resulting in a range of displacements.

• Test method still requires development in regard to testing regime.

•Second site trial of final rig• Conducted at Mine B in Western Australia.

• 7 bolts tested with a total of 12 drops.

• The impact energy ranged between 12-26kJ, resulting in a range of displacements.

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Test results summaryIn-Situ Dynamic testing

0

5

10

15

20

25

30

35

0 100 200 300 400 500 600 700

Ener

gy (k

J)

Displacement (mm)

Energy Displacement Performance

Trial rig site

MD Bolt Mine A (Oct 2013)

MD Bolt Mine B (Dec 2013)

Inflatable bolt (WASM data)

Split tube (WASM data)

Target results (25kJ, 300mm)

Sandvik MD Bolt and In-situ dynamic testing of ground support13

Sandvik MD Bolt and In-situ dynamic testing of ground support14

Future plansIn-Situ Dynamic testing

• Continue to test at new sites with different rock conditions.

• Continue to develop the test rig and process.

• Expand testing outside of Australia.

• Extend the tests to other dynamic bolts.

• Increase the awareness of the advantage of testing ground support elements in-situ.

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Questions