(Pr) 3. Mining Method
Princess Colliery operated for 100 years before its closure in 1974. As a short term replacement, Prince Colliery was opened in 1975. It is located at Point Aconi, about 30 km West of the city of Sydney. During the last 25 years, over 19 million tonnes coal has been extracted from 24 retreat longwall panels. Prince Colliery is an undersea mining operation and is currently working at a depth of 350 m (1148.3 feet) below mean sea level. Mining has been planned historically to avoid areas where the Sandstone scouring is present.
Current workings are about 7 km (4.4 miles) from the sea-coast (Figure Pr5). Mining is presently taking place on #1 North panel. An exploratory drilling program is ongoing to define the northern limit of the Hub River Sandstone. The wall length may be increased from 2743.2 m (9000 feet) to 3657.6 m (12000 feet). After mining #1 North wall, mining will proceed westward in an up-dip direction towards the ocean floor. It is then planned to extract the additional poorer quality coal reserves to the East of the Hub River Sandstone channel.
Initial mining at Prince, was conducted using the mechanized Room and pillar method. Later, the longwall mining method proved successful in the relatively flat (gradient < 5°), fault-free, easily cavable roof of the Hub Seam.
In the fall of 1978, an experimental retreat longwall panel, 60 m (196.9 feet) wide, proved successful. By August 1980, retreat longwall mining was planned with an annual target production of 1 million tonnes of coal. To accommodate the additional ventilation requirement, a 5.2 m (17.1 feet) wide concrete lined air shaft was sunk at the coastline in 1980. Longwal panels were developed on both sides of the main access slopes. As mining progressed towards the MacKenzie Syncline, strata control became more troublesome. Consequently, orientation of later longwall panels was changed to a direction subparallel to the in situ horizontal stress, i.e. North-South.
Early Room and pillar mining employed:
(i) Lee-Norse Continuous Miners
(ii) Wagner Shuttle Cars
(iii) Lee-Norse Roof Bolters.
Current Retreat longwall mining uses:
(i) Eickhoff double drum ranging arm shearer
(ii) Joy Mining Machinery 2 leg 510 tonne capacity powered supports
(iii) Joy Mining Machinery Armoured Face Conveyor with 2-300 HP drives
(iv) Joy Mining Machinery Stage Loaders and Crusher
(v) 2 Huwood 400 HP Bett Conveyor drives with loop take ups on the maingate
(Pr)3.3 Development Method & Equipment
Current Longwall panels (#1 North, #2 North etc.) are being developed towards the North (Figure Pr5). Typical development equipment consists of Dosco Dint Headers with bridge conveyors attached to the belt. The 4.6 m (15.1 feet) wide roadways are driven in 3 passes with 0.9 ~ 1.8 m (3 ~ 6 feet) advance per cycle. (W6 x 25) Flat steel beams are simultaneously installed on steel legs (W6 x 15).