Block Caving & Long Hole Stopping

Block Caving
This is on average the lowest cost per ton underground mining technique that exists. It does have need of extensive upfront development costs as huge excavations need to be made to undermine the block that is to cave, and big milling infrastructure needs to be set up to hold the big ore tonnages that a profitable cave will bring about. Once the ore block has been undermined, the ore block is broken over time by gravity and the pieces fall down the finger raise. The dimension of the pieces that go through to the chutes for loading is controlled by strong sieves or grizzlies on the grizzly level.

Long Hole Stopping
In paces where big blocks of ore can be identified and the adjoining rock is quite strong, then a long hole mining method is by and large the lowest cost mining technique. The result is not unlike an underground excavation. Entrance to the top and bottom of the ore block is established with drifts or tunnels. A vertical hole is produced inside of the ore from the top of the block to the bottom. Long holes are drilled to blast vertical slabs off the ore block. On average a loader takes care of picking up the broken ore from the lower tunnel and takes it away to an ore pass. Due to precautionary motives the loader is operated distantly by a radio control when it is in the large open stope. As soon as the ore block has been blasted and extracted, the stope will usually be filled with waste rock so as to even out the empty space and make way for the extraction of adjoining ore blocks. This mining technique is very well known of, and is nearly the underground analogy to the advances accomplished in automating a great open pit. Where big blocks of ore can be recognized in moderately hard rock this technique is prolific and the cost is low.