ABSTRACT
Large areas of roof rock with very few joints have been exposed in the Muchengjian colliery (China) where non-entry mining faces are employed. Machinery in these non-entry faces is operated from roadways and there is no support. The hard roof rock has been exposed over an area of approximately 5000 m2, which produces high stress zones on coal body and roadways ahead of the mining face. Sudden movement of the hard and thick roof rock would cause significant damage to the mining face and roadways (Vervoort 1991, Kaiser & Chunan 1998). If the movement of the hard roof can be predicted as a function of mined area, a plan can be made to bring the roof down artificially, minimizing the risk of an unexpected collapse. After the first major fall, the roof falls become periodic, a condition which is beneficial and increases the safety of production. 3DEC can be used to study the roof movements numerically. The rock units at the non-entry mining face are listed in Table 1.
