Block caving is a mining method in which ore is allowed to collapse due to its own weight in a controlled fashion into chutes or drawpoints. Block caving is usually used to mine large orebodies that have consistent, disseminated grade throughout. The rock mass must contain natural fracturing in sufficient density such that it will naturally cave when undercut. The caved pieces of rock cannot be too large or they will be difficult to extract from the drawpoints. Successful block caving is dependant upon the joint frequency, joint , and joint characteristics of the ore. The most favourable conditions are a rock mass with two sub-vertical joint sets and a flatter joint set having a dip less than about 30 degrees. Block caving occurs sequentially in segments or blocks 60 to 150 m on a side in all three directions. A series of haulage tunnels are constructed under the ore to be mined. At approximately 30-m intervals along each tunnel in a checkerboard pattern, 3- to 6-m diameter raises connect the haulage tunnels with another series of crosscuts. In the crosscuts, scrapers or LHD's transport the ore back to the main haulage level. The ore falls down finger raises intersecting the cross drifts below. These raises are driven in many directions into the ore above, usually with four or more intersecting at one point in the cross drift. These raises act first as a place to blast the entire underside of the ore block, then later as a funnel to draw the blasted ore. The ore continues to fall under gravity from the bottom of the block as it is pulled from the raises. No further entry can be made in the finger raises once the block begins to cave in. As broken ore is removed, the capping or non-mineral bearing rock above the ore will gradually descend until broken fragments of it start coming from the drawpoints, indicating all of the ore has been withdrawn. There is typically large scale subsidence on surface as a result of block caving. The area of subsidence is usually greater than the caved block but not as deep since it is usually partly filled with collapsed rock from above the cave block. References Hamrin, H. 1982 Hartman (1987) Brady, B.H.G, and Brown, E.T. (1985) Boshkov, S.H.; Wright, F.D. (1973) Lucas, J.R.; Haycocks, C. (eds.) 1973 Morrison, R.G.; Russell, P.L. 1973 Thomas, L.J. 1978 Tobie, R.L.; Julin, D.E. 1982 Weiss, P.F. et al. 1981 | 
