The Gosowong Gold Project is owned and operated by PT Nusa Halmahera Minerals (PT NHM), an Indonesian company 75 per cent owned by Newcrest. It is located on Halmahera Island, in the North Maluku Province of the Republic of Indonesia, approximately 2450 km north-east of the national capital, Jakarta (Newcrest, 2017).
Kencana is one of two underground gold and silver mines at the Gosowong Operation where ground conditions vary from competent to very poor. Development headings occurring in poor rock mass conditions require high capacity ground support including long tendon cable bolts. Manual installation of cable bolts in these development headings has been a time consuming process due to borehole collapse, blockages requiring subsequent re-drilling and a minimum eight hour grout curing time interval. The installation of cable bolts including the setting, plating and tensioning can impact the critical path for development heading advance resulting in development cycle delays.
A review was conducted by PT NHM on current industry practices for alternatives to manual cable bolting. PT NHM subsequently approached Minova to assist with the development and trialling of self drilling anchors (SDAs) installed using jumbos with a rapid setting pumpable resin, CARBOTHIXTM. A series of system development trials were conducted and a reliable bolting system was developed utilising the existing jumbo drilling fleet with minimal required modifications.
The system developed was a ‘one pass’ bolting process to
install and grout SDAs using a two component resin with a remote, mechanised
system. Improvements achieved from the system include:
- eliminating hole closure issues and more immediate support in poor rock
- effectively reducing personnel exposure to poor ground conditions by
removing the requirement to access the drive backs
- reducing grout set time with full installation times for 6 m SDAs
averaging 25 min.
The resin grouting system has now been successfully implemented to effectively manage areas of poor ground conditions and to accelerate advance rates in high priority headings.
Pateman, D and Sprague, T, 2017.
Development and implementation of a long tendon bolting system utilising resin
grouting technology, in Proceedings 13th AusIMM Underground Operators’
Conference 2017, pp 79–84 (The Australasian Institute of Mining and Metallurgy: