retreating longwall method

The retreating longwall method is a technique used in underground coal mining where large blocks of coal are extracted in slices. This method involves developing a block of coal to its boundary and then mining it back towards the main haulage tunnel.1

In mechanized operations, continuous miners called shearers or plows cut and load the coal onto a face conveyor. The roof is supported by self-advancing shields that create a protective canopy. This system allows for high production rates.1

Longwall mining was introduced in the 17th century and became more productive with the development of plows and shearers in the mid-20th century. The retreating method is common in the United States, while the advancing method is more prevalent in Europe. This method typically causes surface subsidence due to the caving of overlying strata.21