**2.3 Wongawilli mining**

Australia has a history of successful pillar extraction over 90 years. In 1952, the first continuous miner was introduced at Wongawilli colliery and Huntley colliery. In 1955, they were also introduced in South Clifton colliery, Old Bulli colliery, Nebo colliery, and Kemira colliery, and later on, many continuous miners came into existence. The Wongawilli method was first adopted in Wongawilli colliery in 1958. Since then, this method has been gradually modified to suit both the mining conditions and the development of mining machinery [28].

This method provides a single working place and extraction of coal in stress relieving area. This system can be easily understood and followed by employees. With the Wongawilli system, an overall percentage of extraction of 80−90% can be expected,

#### **Figure 4.**

*Conceptual model of longwall top coal caving (after [23]).*

### *Underground Coal Mining Methods and Their Impact on Safety DOI: http://dx.doi.org/10.5772/intechopen.109083*

with improved worker safety, minimal development workings required, and high production rates achieved. The machinery used for panel development consists of two shuttle cars and a continuous miner. This system is straightforward, repetitive, and easily understood by the employees. The difficulties usually occur in lifting the final stooks at the end of each fender. This method maintains a straight line of extraction, which is helpful in mechanized depillaring in caving. The success of this method was working within distressed areas and can be adopted successfully to a depth of up to 600 meters. This method has been successfully practiced in Australia for over 90 years [29, 30]. The basic layout of the Wongawilli system of extraction is shown in **Figure 5***.*
