Vol 48 Iss. 1

When developing powerful steeply falling formations with the division of the floor into sub-floors (for example, at hydro-mines), effective means of supporting the sub-floor drifts are required. The support should provide reliable stability of drifts and ease of its installation - conditions for high rates of drifting by shearers or hydro-monitors. The type of such support depends primarily on the amount of rock pressure, which is the result of the distribution of stresses in the rock mass around the excavation.

One of the main obstacles to the introduction of mechanized fasteners in weak host rocks is the lack of data on the relationship between the magnitude of rock pressure taken up by the fastener and the area of the fastener. The present article is devoted to the determination of soil resistance to indentation depending on the diameter and material of a round die (metal or wood).

In clayey rocks under the action of a certain shear stress τ creep deformations develop in time. At values of shear resistance t, less than some value creep deformations have a damping character. When exceeded, creep deformations are not damped, and in plastic or frozen clay rocks their development in time leads to rock failure. The greater the magnitude of the shear stress, the earlier the clay rock fractures.

General characteristics of clayey rocks. Lignite deposits of the Moscow region are located in complex engineering and geological conditions, without taking into account which mining and cleaning works are extremely complicated. Among the phenomena causing difficulties in the development of the fields is the swelling of clayey rocks exposed by mine workings. Plastic clays are the most widespread among the clayey rocks of the coal-bearing horizon of the Moscow Region. They are the main host rocks for coal deposits, composing their soil and roof, or forming intercoal interlayers.

In the development of coal seams with the use of flexible slabs and various kinds of shields is often necessary to correctly determine the lateral pressure of the tab on the vertical or inclined walls. Methods of determining the value of vertical pressure are mainly covered in the technical literature. Much less investigated is the lateral pressure, which can be considered as a consequence of spacing between pieces of rock under vertical load.Studies show that the state of the bulk material has a great influence on the magnitude of the lateral pressure. When the bulk material transitions from a stationary to a mobile state, the degree of its loosening increases and the value of lateral pressure increases significantly. Meanwhile, the known calculation formulas are built on the basis of schemes that provide a stationary equilibrium state of the bulk solids, so their use does not provide the correct solution in all cases.

Determination of mechanical properties of rock massif in full-scale conditions is a complicated and still unsolved problem. Therefore, when solving practical problems as a characteristic of the strength of rocks are used indices of time resistance to uniaxial compression and tension, obtained by testing samples of these rocks, taken from the most characteristic places of the massif. However, this raises the question of the legitimacy of extrapolation of the results of laboratory tests of samples on rock massifs.

Among the development systems used in Kuzbass on thick steep formations, the shield system is especially widespread. In this system, more than 40% of all preparatory workings are made up of coal-fired and traveling furnaces. Furnace maintenance conditions are one of the most important tasks.

In the current seven-year Tenteksky and Churubay-Nurinsky coal districts are the main areas of construction of new mines in the Karaganda basin. Conditions of maintenance of horizontal and inclined mine workings at the mines under construction are as diverse as physical and mechanical properties of rocks in which these workings are sinking. Maintenance of rolling mine workings of Tenteksky district does not present great difficulties, as sinking is carried out mainly in strong stable rocks. The most difficult conditions for maintenance of mine workings of Karadzharo-Shakhansky section of Churubai-Nura district, especially at ventilation horizons. Fasteners installed here (solid wooden, metal, prefabricated reinforced concrete, etc.) due to high all-round pressure are deformed and must be replaced. Most of the mine workings were reinforced several times during the construction period. Reinforcement works require large expenditures of labor, time and money.

The combined chamber-lava system combines elements of the pillar and chamber systems. The system has the following characteristic features: the main roof is supported for a long time by specially left supporting pillars; to increase the bearing capacity of the immediate roof and to control the condition of the roof in the excavated space, a light wooden support is installed, designed to support only the lower layer of the immediate roof with a thickness of no more than 4 m, the face of the chamber-lava with a total length of up to 215 m is moved in the same way as the longwall face excavation - by parallel drifts in one direction; the bottom-hole space is not fixed at all, and its width is 3.4-3.8 m.

One of the urgent problems of further development of the Churubai-Nurinsk region is the development of rational types of supports. Data on the manifestation of rock pressure in preparatory workings can be obtained by an approximate calculation method. It is necessary to determine the amount of load on the support of horizontal workings (in the conditions under consideration) depending on the physical and mechanical properties of rocks surrounding the workings, the size of the workings and the depth of its embedment from the surface, as well as the design of the support, i.e. the main factors that can be easily determined in production conditions. To solve this problem, the results of mine and laboratory studies, as well as the previously stated data are involved. In addition, the existing analytical calculation methods were used. The results of determining the value of vertical load according to these methods, as well as the results of direct measurements of the value of load P on the support with the help of dynamometers in the conditions of the ventilation horizon of mine No. 14 “Churubai-Nurinskaya” are given in the table.

Mining of steep seams in strips along the dip by shield complexes is a fundamentally new direction of mechanization of coal mining. The interaction of shielding with side rocks is poorly studied and is decisive in the design and selection of basic parameters of shielding.

The chamber-shield system with the use of mobile shields was proposed for the clearance excavation of thick gentle strata. Production tests of such a system (1959) with the shield LGNK-1 confirmed the high efficiency and serviceability of the mobile shield type.

To reduce coal losses at hydraulic development of powerful steeply falling seams by the system of sub-stage hydraulic stripping flexible metal overlaps are used, separating coal from the collapsed rock and, along with the completeness of extraction, allowing to carry out coal excavation in the absence of fasteners in the clearing space.

It is known that the strength of rod locks fixing is one of the most important conditions for the performance of the rod support. Soviet and foreign researchers differently define the parameters of metal wedge-slot boom locks. The use of such rods is considered expedient mainly in rocks of medium strength (with a coefficient of strength f according to M. M. Protodyakonov from 5 to 8) and to a lesser extent - in strong rocks (f from 8 to 12). However, to date there is no published methodology, simple and convenient for practical calculations.

The correct choice of the direction of the clearance excavation largely determines the amount of bearing pressure on the pillars and the ore massif adjacent to the excavated space, and the manifestations of bearing pressure determine the safety of excavation and the amount of ore losses. This factor becomes especially important in the development of fractured unstable ores. The Norilsk copper-nickel deposit develops mainly disseminated ores, which are mineralized gabbro-diabases. Some sections of the lower part of the ore body contain continuous sulfide ores.

During the open-pit mining of the Tikhvin bauxite deposits, where production is expected to increase significantly in the near future, breaches of the sides and outer dumps occur at a number of open-pit mines. At some mines (9, and to a lesser extent 6, 13 and 3) landslides and slumps significantly complicate the organization of work at the open pits and increase the cost of bauxite.