Vol 36 Iss. 1

In 1957, the Institute lost an outstanding teacher and researcher, a major specialist in the development of ore deposits, associate professor, candidate of technical sciences Nikolai N. Polyakov.

In 1957, Alexander M. Alamsky, a prominent specialist in the field of mining, an indefatigable researcher and a talented teacher, associate professor of the Drilling and Blasting Department of the Leningrad Mining Institute, candidate of technical sciences, passed away. He was born in 1900 in the town of Atkarsk, Saratov province. He was educated in a real school, Saratov University (two courses), Saratov Polytechnic Institute and, finally, in 1928 Alexander Mikhailovich graduated from the Leningrad Mining Institute, specializing in the development of ore deposits.

Rock fracturing is a general property of a rock massif characterized by ubiquitous distribution and irregularity of development, as well as a pronounced average orientation of fracture systems within geological structures. The intensity of fracturing is determined, as observations show, by the composition of rocks and conditions of their occurrence. The aggregate of fracturing of individual layers, strata and stratigraphic horizons gives the fracturing of the rock massif. Being an important structural element of the rock massif, rock fracturing, especially in the conditions of folded coal deposits, is a constantly acting factor on affecting the development conditions.

Modern systems of development of thin and medium thickness steeply dipping coal seams, despite continuous improvement, have major drawbacks. They do not guarantee complete safety of labor, a continuous flow of coal excavation is not achieved, labor productivity continues to be insufficient. This is due to the fact that when working along the strike and with the applied methods of roof management, significant exposures of the host rocks are required, and therefore conditions are created that lead to face blockages and high labor intensity of the main production processes.

One of the most important places in the complex of production processes of coal mining are occupied by support and roof control in longwall faces. The work on support and roof control are associated with high labor and timber costs. The main means of reducing the cost of support and roof control is the wide introduction of mechanized support and metal organ walls. As industrial tests have shown, the best technical and economic indicators are obtained with organ walls OK and OKU‑150. This kind of support became the most widespread. As of July 1956, 182 faces in the Ukrainian Donbass and about 50 faces in the Rostovugol Combine were secured with the OK and OKU‑150 organ walls. By the end of 1957 it is planned to introduce this support in 600 faces in a number of basins of the Soviet Union.

At the end of 1955, the Leningrad Mining Institute was involved in the work of the Unipromed Institute to improve the development systems at copper mines in the Urals. The proposed article deals with one of the issues studied by the Institute. The work was carried out by Associate Professor N. N. Polyakov. N. N. Polyakov, Associate Professor E. Y. Makhno and the author of the article under the guidance of Prof. P. I. Gorodetsky. The design of the mobile support and flexible covering was developed jointly by Associate Professor E. Y. Makhno and the author, all laboratory experiments, observations at the mines and calculations were performed by the author of the article.

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, support of working faces. Therefore, it is very tempting and promising to study the possibility of layer mining with the use of only one flexible covering. In this case, the working space of the face will be between the sagging part of the flexible covering ab and the face wall av. A 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.

The economic significance of qualitative and quantitative mineral losses during mining is well known, and therefore the importance of their regulation is obvious. Although mineral losses and dilution during mining are inevitable, their size can be different, and the possibility (and the degree of technical complexity) of reduction depends, on the one hand, on natural conditions, and on the other hand - on the development system, the quality of mining operations and the quality of their control and accounting.

The increase in coal production by open-pit mining envisaged by the Five‑Year Plan (122 million tonnes in 1960 against 66 million tonnes in 1955) in rate far exceeds the general growth of coal production in the Soviet Union, and especially from underground work: open‑pit coal production increases by 88%, total production by 52%, underground production by about 40%. Such an increased rate of development of open‑pit works is connected with their well‑known advantages, consisting, besides increase of labor productivity and reduction of production costs, in considerable improvement of labor conditions, increase of safety of works and sharp reduction of losses in the subsoil, especially at the development of powerful steeply dipping seams and veins. Injuries at coal pits are about five times less than in underground mines (reduction of severe and fatal cases is even greater).

Establishing the cost of drift repair has always been and continues to be given much attention in mining engineering literature, as the maintenance of drifts is one of the main expenditure items of coal mines both in terms of cost and labor intensity. Some establish a mathematical dependence of the cost of drift repair for drifts driven (or closed) parallel to stoping operations as a function of their length, and others – as a function of maintenance conditions: the cross‑section of the working, rock characteristics, proximity to stoping operations, etc.

The importance of preparatory workings in increasing labor productivity in the coal industry is great. Being ahead of cleaning works, preparatory workings create coal reserves, ready for excavation, than provide normal and uninterrupted operation of the field, rational use of mechanisms and high labor productivity in cleaning works.

In order to provide stoping and preparation faces with sufficient amount of air it is necessary to correctly determine air losses both at operating mines and at their design. In many mines of Donbass, as well as in other coal basins of the country, a significant proprotion (often reaching 50-70%) in the general mine underground leakages falls on air losses in parallel workings.

At present, there is an urgent need to create roadheaders for driving mine workings in medium‑hard and hard rocks. One of the possible solutions to this issue is the creation of a roadheader that destroys rock by percussive action. The development of the design of the working element of such a machine is complicated by insufficient study of rock destruction under impact loading and the lack of parameters necessary for design. For this reason there are still no satisfactory designs of impact mining machines, despite the fact that the first inventions in this field appeared more than a hundred years ago (for example, the Penrice tunneling machine of 1856).

Further realization of the grandiose tasks of the peaceful development of the national economy of the USSR requires an even wider use of explosives energy in the development of mineral deposits in the field of industrial, railway and hydraulic engineering construction and in other sectors of the economy. Meanwhile, the issue of determining the size of explosive charges is still far from being sufficiently developed, and existing methods of calculation often give incorrect results.

Of all the currently known methods of sinking mine shafts, only the drilling method mechanizes all the main links of the driving cycle and allows automation of production. Drilling method, as well as other special methods of excavation, is applicable in difficult mining‑geological conditions (for example, large inflows of water into the excavation). However, in comparison with the methods of freezing and cementation, it has a number of advantages. By this method, rock destruction, its removal and temporary support are carried out in parallel and with the help of mechanisms controlled from the ground surface, i.e. the most labor‑intensive and dangerous profession of a shaft sinker is eliminated.

Cleaning the bottom hole of drilled rock and bringing it to the surface when drilling shafts and boreholes is one of the main functions performed by the flushing fluid. In the process of drilling, the flushing fluid is contaminated with drilled rock and its percentage in the fluid increases. The high content of drilled rock in the flushing fluid deteriorates its quality, causes collapse of the borehole walls (due to deterioration of the clay coating on its walls) and poses a risk of seizing the drilling tool when flushing is stopped. Besides, the increase in the percentage of rock content in the flushing solution requires more energy for flushing, increases the wear of drilling equipment parts, and significantly reduces the drilling speed.

In 1955, the VNIMI team, in the work of which the author was directly involved, surveyed 70 of the most disturbed mine shafts in Donbass. For the remaining shafts, questionnaires on the condition of the shafts were collected with the corresponding graphic materials attached. The survey covered almost all natural conditions in which there are mine shafts of Donbass with the depth of more than 300 m.

In the practice of mine shaft equipment design up to the present time, the calculation of equipment elements is made according to the norms based on the “Prussian rules for lifting and lowering people” from 6/IV 1925. For example, in 1934 S. L. Lazovsky drew attention to the fact that due to the elasticity of conductors the load is distributed unevenly between the buntons and gave a solution to the problem of load distribution between the buntons taking into account the elasticity of conductors.

Core drilling has found wide application in geological exploration and the mining industry. The fleet of core drilling machines is replenished with new models. There are units for drilling in the most varied geological conditions and at the most varied depths of wells (from 50‑100 to 1000‑1500 m and higher). However, despite the large volume of drilling operations and their long application, very little attention has been paid to the issues of drilling rig drives. The proposed paper addresses part of the general issue of the power required for the well drilling process.

The present work is based on time study materials conducted by the staff of the All‑Union Research Institute of Methods and Techniques of Exploration (VITR) in the Karaganda coal basin and the Kustanay iron ore deposit. The structure of the deposit of the Dolinsk section of the Karaganda basin involves Quaternary, Tertiary and Paleozoic sediments. Quaternary sediments are represented by modern continental facies – mainly alluvium, deluvium and proluvium. The upper part of the Quaternary sediments consists of sandy loam, loam and variably grained sands with inclusion of pebbles. The thickness of sediments is from 7 to 15 m.

So far, the main means of drilling holes for blasting operations at open‑pit mines are percussion drilling machines. More than 1,500 machines operate at mines and quarries, with a total drilling volume exceeding 3 million linear meters of wells per year. Increasing the productivity of the machines and improving drilling operations have been given much attention in recent years, but drilling productivity still grows very slowly. At mines with good organization of drilling operations, where machine downtime is minimized, drilling productivity has practically not increased in recent years, i.e., the reserves for increasing productivity through organizational measures have been largely used up. To further increase productivity, it is necessary to modernize the machines.

The solution to the problem of transportation of large volumes of rock mass at open‑pit mining operations depends to a great extent on increasing productivity and reducing the cost of rail transport. An important role should be given to the improvement of wagon designs, which account for 65% of metal consumption and up to 40% of maintenance, repair and depreciation costs in relation to the total costs of rolling stock. As the analysis of transportation equipment operation at open pits shows, the current situation with the equipment of open‑pit mining operations with dump cars cannot be considered satisfactory: a) the range of manufactured dump cars is small; b) the strength of the main components of the wagon is low in general, and especially when excavators with large bucket capacity are used for loading; c) the tare coefficient and the length of the wagon are high; d) the operating costs of the wagon fleet are significant. Therefore, it is necessary to design and manufacture new types of dump cars for open‑pit mining operations.