BIT SELECTION AND DRILLING

To select the correct drill bit diameter for meeting the recommended initial anchorage of 6 to 9 tons, drill several holes with bit diameters ranging from 1-518 to 1-314 inch (41 to 45 mm).

  • Drill each hole at least 2 inches (5 cm) longer than the bolt length.
  • Number each hole and record the bit size.

In soft ground, a bit may drill a hole larger than its diameter. In hard abrasive ground, the hole may be the same diameter as the bit.

Drive into each hole an SS-46 Split Set stabiliser fitted with a pull collar as shown.

  • Record the driving time for each stabiliser. After insertion, observe the amount of slot closure inside each stabiliser.

To determine anchorage, perform a pull test.

  • Align the pull tester with the stabiliser, and pressurize it until the stabiliser slips in the hole.
  • Watch to be sure that it is actually the stabiliser that has slipped. (When building up the pull load on the stabiliser, various adjustments may occur such   as   realignment   of   the   tester housing, bearing plate settling, or localized rock crushing. These must not be mistaken for tube slippage.)

Once the bolt has slipped in the hole, pressurize the tester pump until the bolt slips again. The same pull load should cause subsequent slippage.

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INTERPRETING TEST DATA

After the above pull tests are completed, draw two graphs:

  • Spacer (a) Anchorage versus bit diameter.
  • Pull collar (b) Anchorage versus driving time.

Use the first graph to determine the correct bit size for your particular ground condition. As the bit wears, the hole will become smaller and friction will increase until the bit is replaced or the drill can’t drive the bolt completely.

Use the second graph to establish correct driving time required for this ground and bolt length. With a given bit, drill, bolt length, rock characteristic and constant pressure, insertion time will be proportional to initial anchorage.

It’s important to establish this data for use in later spot checks, to assure that proper installation techniques are still being used.

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ORDER INFORMATION

SS-46 Weight kg CPN
pull collar galv 0.2 89717508

STABILISER INSTALLATIONS FOR HAND MACHINE INSTALLATIONS

  • Drill a hole slightly smaller in diameter than the Split Set stabiliser. The recommended bit diameter for SS46 Split Set bolts is around 41 to 45
  • Ensure that the hole is drilled slightly deeper than the complete length of the bolt. This will allow the unit to be driven in again in areas where the collar may spall
  • Attach the appropriate driver tool. Check the condition of the driver tool, excessively worn driver tools can damage the unit during
  • Align the unit with the drilled hole and drive it
  • Check the time that it takes to completely drive the unit into the hole. The time taken to drive the unit in will be a guide as to the load that the fixture will be
  • A driving time of more than 15 – 18 seconds will generally result in a fixture holding around 10
  • In soft ground it could be necessary to reduce the bit diameter to increase the driving time thus increasing the load the bolt will
  • Drive times of less than 15 seconds will usually result in a fixture that will hold less than the recommended load.
Townsville – North Queensland

Phone: (07) 4774 6464 (Option 3)
Fax: (07) 4774 6939

Perth - Western Australia

Phone: (08) 9458 1188
Fax: (08) 9458 1182

Sydney - New South Wales

Phone: (02) 9832 3377
Fax: (02) 9832 0733

Brisbane - SE Queensland

Phone: (07) 4774 6464 (option 3)
Fax: (07) 4774 6939

Townsville – North Queensland

Phone: (07) 4774 6464 (Option 3)
Fax: (07) 4774 6939

Perth - Western Australia

Phone: (08) 9458 1188
Fax: (08) 9458 1182

Sydney - New South Wales

Phone: (02) 9832 3377
Fax: (02) 9832 0733

Brisbane - SE Queensland

Phone: (07) 4774 6464 (option 3)
Fax: (07) 4774 6939