Block shrinkage

 The scheme for the shrinkage of the ore, which is being broken from the retreating stopes: 1 - the massif of the ore; 2 - the blasting boreholes; 3 - the raise; 4 - the ceiling; 5 - the virgin rock pillar; 6 - the walking drift; 7 - the ventilation drift; 8 - the haulage drift.

BLOCK SHRINKAGE (EN: block shrinkage, block shrinkage stoping; DE: Magazinblockbau, Blockspeicher; FR: exploitation par chambresmagasins; ES: almace namienro del mineral en blogue; RU: блоковое магазинирование) is the accumulation of the broken ore within the goaf space of the retreating mine working for the entire height of the block (level).

It is used during the development of the depositions of the strong ores, which are not prone to caking and oxidation, within the stable country rocks. In case of the block shrinkage, the height of the block is usually 40-50 metres, the length is 50-70 metres, the distance between the output holes through the bottom is 4-7 metres. They place the blocks along or across the line of the strike of the deposition. The breaking of the ore is performed from the retreating stopes and preparatory mine workings. In the first case, they perform it using the small blasting borehole method (see the Figure); the line of the stope is continuous (mainly) or with the ledges at the ceiling; they partially output the ore from the storage after the breaking of this ore throughout the entire stope; there is possible the sorting of the ore.

During the breaking of the ore from the preparatory mine workings, which have been headed for the height of the block (level), the shrinkage and output of the ore are performed continuously. The block shrinkage, in comparison with the other types of the shrinkage, distinguishes itself with the relatively high technical-economical indicators: during the development of the strong ores within the depositions with the thickness of 0.2-1.5, 2-5, and 7-10 metres, the productivity of the labour of the worker within the stope is, respectively, up to 15, 30, and 40 tonnes per shift. The losses and dilution of the ore during the block shrinkage decrease with the increasing of the thickness of the depositions, which are being developed.The shrinkage of the ore, which is being broken from the retreating stopes

The scheme for the shrinkage of the ore, which is being broken from the retreating stopes:

  1. - the massif of the ore; 
  2. - the blasting boreholes;
  3. - the raise;
  4. - the ceiling;
  5. - the virgin rock pillar;
  6. - the walking drift;
  7. - the ventilation drift;
  8. - the haulage drift.