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.

During the last decade flexible shields have become widespread in the development of steeply dipping coal seams in Kuzbass, where they successfully compete with other methods of development. Shield mining in the ore industry in many cases can replace low-productive and expensive mining by layer caving.

Layer caving is in many cases the only acceptable mining system, so the issues of improving its efficiency are of great practical importance for the ore industry. However, this system is characterized by low productivity of the faces and high labor intensity of works, in particular, fixing of cleaning faces. Therefore, it is very tempting and promising to study the possibility of layer mining with the use of only one flexible slab. In this case, the working space of the face will be between the sagging part of the flexible slab ab and the face wall av. Successful solution of the problem would make it possible to work the layers in a very simple and cheap way and thus significantly increase the efficiency of the layer caving system.

Improving the systems and methods for developing thick flat dipping seams is one of the most difficult and at the same time urgent tasks facing the coal mining industry at the present time. The most rational system for developing such seams is usually considered to be inclined layer mining with roof caving, which has become widespread in the industry. Engineering analysis shows that this system has a number of shortcomings. The issue of creating a rational system for developing thick flat dipping seams cannot be considered resolved. A rational system for developing thick flat dipping seams should provide for the exclusion of manually erected support in the working face, as well as the use of a large seam thickness. Among the possible solutions to this problem, the system for developing thick flat dipping seams with forced coal caving is particularly simple.

The greatest difficulties in the coal industry are presented by the development of thick steeply dipping seams. Development of thick seams usually involves high labor costs, significant timber consumption and entails greater coal losses than when developing seams of average thickness. Cases of self-heating of coal and underground fires occur more often when developing thick seams. Therefore, significant material costs are incurred for carrying out preventive measures and extinguishing fires, which increases the cost of coal and often leads to very significant losses of minerals. A major achievement of Soviet mining technology is the shield system of Professor N. A. Chinakala. It has found wide application in the mines of Kuzbass. The decisive factor that determined the high degree of reliability of the shield of Professor N. A. Chinakala, the rapid and wide introduction of this shield in the mining industry, is the direction of its movement down the dip of the seam. The proposed work is an attempt to shed light on issues related to the improvement of the design of shields and the possibility of their use in the development steeply dipping, very powerful strata.

The urgent task is to create and implement reliable and highly productive methods of mechanized fastening of working faces. The article presents various types of shield support for the development of thin and medium-thickness steeply dipping seams in strips down the dip: 1) sectional shield support; 2) U-shaped shield; 3) L-shaped flexible shield; 4) self-braking shield. The horizontal arrangement of the working face and the development of the seam in strips down the dip significantly facilitate the creation of a simple and efficient shield support. In order to reduce the load on the shield elements, reduce metal consumption and ensure the most reliable operation, it is necessary to prefer flexible shields consisting of support frames or short sections (0.5-1.0 m) connected by a flexible connection. With a seam thickness from 0.6-0.8 to 3.0-4.0 m, the use of L-shaped shields is most appropriate. U-shaped shields are less rational due to their excessive bulkiness and difficulty in controlling them when lowering. The proposed shield support can be used in the development of steeply dipping seams with a thickness of 0.6-0.8 to 3.0-4.0 m, with an angle of incidence greater than 50-55° and with medium-hard and strong wall rocks.

In the coal mining industry, the development of thick seams presents the greatest difficulties. In the matter of improving the methods of developing thick steeply dipping seams, the most promising direction should be considered the improvement of known and the creation of new systems that provide for the development of the seam without dividing it into layers with maximum use of natural conditions: high seam thickness, steep dip, etc. Systems for developing thick steeply dipping seams without dividing them into layers, in turn, can be divided into three groups: 1) systems that provide for the development of the seam with chambers (systems of engineers I. N. Koznin, G. A. Lomov, and others); 2) systems that provide for the development of the seam in strips along the dip or rise (the system of Professor Chinakal, the VUGI system); 3) systems that provide for the development of the seam with long columns along the strike (the system of engineer P. I. Kokorin, and others). The proposed article is devoted to the third group of systems that provide for the development of thick steeply dipping strata with long columns along the strike without division into layers. These systems are distinguished by their greatest simplicity, versatility and high efficiency.

The main disadvantage of the existing methods of developing thin and medium-thick steep coal seams is the use of wooden supports in the working faces. Support of the working faces is carried out exclusively by hand and is the most dangerous, difficult and labor-intensive operation. Thus, labor costs for support, timber delivery and control of rock pressure usually make up 50 to 80% of the total labor costs in the working face (see article). A miner spends about two thirds of the net working time on support. If we also take into account timber delivery and work on managing rock pressure (installation of organ support, etc.), then the total time spent on these operations, including support, will amount to approximately 80% of the total labor costs in the working face for coal mining. In the Donbass, chipping hammers are predominantly used, which determines a significantly higher labor intensity of coal mining work. Therefore, work related to support and rock pressure control here makes up approximately 50-60% of the total labor costs in the working face. But in the future, in connection with the introduction of combines, the specific weight of these works will increase significantly and will also reach 80-85%.