CASE STUDY

Development of a One Pass Bolting System PT Nusa Halmahera Minerals – Kencana Mine, Indonesia

Page 1 | Document reference: 200375

Site Profile Kencana Mine is an underground mine situated on the

Island of Halmahera which is part of Maluku Province,

Indonesia. The Kencana Mine is owned and operated

by PT Nusa Halmahera Minerals (PTNHM). PTNHM is

a joint venture company between Newcrest Singapore

Holdings Pte Ltd (a wholly owned subsidiary of

Newcrest Mining Limited) 82.5% and PT Aneka

Tambang Tbk 17.5%. Production at the Kencana Mine

commenced in 2009 and its primary products are Gold

and Silver.

Conditions in the Kencana Mine vary significantly

throughout the underground workings. Roadways in

some areas are subject to excessive wall “squeeze”.

The roadways in these areas need enlargement to the

original profile in order to maintain vehicular access to

the mine workings. Installation of ground support can

also be difficult in these areas, particularly maintaining

an open hole between drilling and insertion of the

ground support. This causes delays in the installation

of ground support due to hole collapse which in turn

affects production. Where cement grout is used, there

is a standard wait time between grouting and

continuation of Operations of 8hrs to allow for curing.

Figure 1: Shank adaptor on a jumbo

The Situation Orica were approached by the Geotechnical

Department at the Mine to help with developing a

support system utilising Self Drilling Anchors (SDA’s)

and Carbothix™ Resin to achieve the following:

Installation of SDA’s from 3m to 9m in length

Reduce installation time

Reduce wait time for grout curing to zero

All operations to be carried out by the drilling jumbo

with minimal manual handling

Eliminate use of ancillary equipment (IT, EWP and

Solo longhole drill)

Technical Solutions Following initial trials at Kencana Mine in October

2013, Orica undertook to perform several actions in

order to improve the system.

Action 1: Modify the T38 to R32 shank adaptor to,

Prevent unwinding from the R32 SDA

Pass through jumbo stabiliser

Ensure maximum penetration of SDA into the rock

Action 2: Design an injection adaptor that:

Can be fitted to the SDA by fitting it to the T38 to

R32 shank adaptor

Does not require “screwing” onto the SDA

Can withstand pressure of pump up to 120 bar

pressure without leakage

The main aims of these trials were to:

Allow all operations to be carried out from the

ground using Jumbo only

Prove design of shank adaptor by allowing quick

detachment from SDA

Prove design of Injection adaptor by fast fitting

removal to/from the SDA

Prove design of injection adaptor by pumping

Carbothix™ resin to 120 bar without leakage

Speed up process of installation, grouting and

tensioning of SDA’s

Make ongoing modifications to improve system

CASE STUDY

Development of a One Pass Bolting System PT Nusa Halmahera Minerals – Kencana Mine, Indonesia

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Page 2 | Document reference: 200375

The Result

SDA’s ranging from 6m to 9m were installed at various

locations in the mine with the following results:

All the key aims of the trials were met

T38 to R32 adaptor worked well, even without

retaining pins, disconnection was reliable and quick

Type 1 injection adaptor worked well, was quickly

fitted and removed from shank adaptor easily and

could be easily guided onto the SDA by the Jumbo

operator unaided

Carbothix™ 1:2 worked well even in extremely hot

environmental conditions

Ground support installation times decreased

significantly throughout trials due to:

One pass system

Rapid set time of Carbothix™

All steps in the process were carried out by the

jumbo and jumbo operator.

Average time to fully install and plate a 6m SDA

was 25mins including setup time.

Testimonial Orica ground support have impressed me every step

of the way since I initially made contact with them.

Their technical team listened to our needs, considered

the options, and then set out in full partnership with us

to develop a practical solution. This bolting and resin

system has allowed us to improve production, safety

and geotechnical stability - it is a big success story for

Kencana and the PT. NHM team. Given our

remoteness on an island in Eastern Indonesia, it was

crucial to get the full support and commitment that

Orica provided us with.

Tony Sprague – Principal Geotechnical

Superintendent, PT. NHM

Acknowledgements Orica wish to thank PT Nusa Halmahera Minerals for

their support and permission to publish this case study.

Figure 2 : Grouting adapter connected to shank adapter

Figure 3: Shank adaptor, grouting adaptor and static mixer