Strong gentle strata in the USSR and abroad are developed mainly by inclined layers with roof collapse. In this system of development rack fasteners in cleaning faces allows to lay in each upper layer of wooden planking or metal mesh, which eliminates coal losses in the thickness of the seam and provides high completeness of excavation. But the use of rack support requires significant costs, heavy manual labor and reduces the production capabilities of the system, which in this form can not meet the requirements of the current period. ...

The problem of development of thick steep seams with backfilling has become especially acute in Kuzbass, where due to a number of circumstances of technical nature it is required to significantly expand its use, while coal mining with backfilling is developing here very slowly. The unpopularity of backfilling in Kuzbass is explained, first of all, by the low efficiency of the mining systems used there. Thus, excavation of thick steep seams with backfilling is still carried out by the old systems, with division into layers.

Bulk rock is characterized by the following: 1) loose rock massif consists of separate, not connected with each other pieces of hard rock; 2) pieces of rock are small enough in comparison with the width of excavation, which practically excludes the possibility of vaulting; 3) the shape of pieces and their location determine the possibility of lateral spreading forces by mutual wedging under the action of load. Often it is necessary to support excavations under the collapsed rock or stockpile, the properties of which are often close to loose rock.