Self Drilling Rock Bolt Technology Development - Stage 1

Underground » Roadway Development

Published: June 02Project Number: C11004

Get ReportAuthor: Peter Gray | Ground Support Services

The results from this project are the culmination of four years of research by Ground Support Services Pty Ltd (GSS) into the Hot-Roll Forging process (HRF) for the production of hollow steel bars for use as Self Drilling Rock Bolts (SDRBs). This pioneering research shows for the first time how a thick-walled, hollow-bar, strong enough for use as a SDRB, can be manufactured economically.

The high cost of steel hollow-bars currently prevents the use of SDRB technology in the Australian coal industry.

In order to reduce the cost of producing hollow bolts, this research focused on the current lowest-cost production method for the manufacture of solid steel rock bolts; namely, the steel hot-rolling production method.

This research has successfully shown how hot-rolling and hot-forging can be combined to produce economic hollow-bars suitable for self-drilling rock bolts. It has obtained and resolved specific hot-rolling design parameters.

A hot-roll research program was drawn up. Steel manufacturers provided consultation and advice. The program comprised simulating the last two hot-rolling stands in a steel mill, using the single rolling stand at the CRC for Welded Structures at the University of Wollongong. Custom-made steel rolls were machined up to form hollow-bars. A series of trials were undertaken. Bars were heated in a furnace and hot-rolled through the machined passes in the rolling stand.

This research proves that a hollow-bar can be hot-rolled:

  • without the central hole collapsing;
  • with ribs formed on the outside of the bar;
  • not have flash on the inside of the hole or on the outside of the bar;
  • maintain a reasonably-consistent bar section and hole size along the bar; and,
  • produce a hollow-bar that will withstand at least 350Nm of torque.

These successful results are outlined in detail in this report.

This project was designed to be a small, short-term project lasting 6 months. It was an essential first step - Stage 1 - in the development of Self-Drilling Rock Bolt Technology. This project was completed in 6 months and has achieved successful results.

The total funding provided by ACARP for this project was $41,600. This funding was based, in part, on a costing provided by the CRC for Welded Structures and on a start date given by the Department of Mechanical Engineering at the University of Wollongong.




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