Vol 64 Iss. 1

The Department of Construction of Mining Enterprises (CME) at the Leningrad Mining Institute was organized in 1947. Its head from the moment of its organization to the present day is Professor B.V.Bokii. At first he was the only teacher at the department and read all special disciplines of mining profile for the specialty Construction of Mining Enterprises and the course “Conducting and fixing of mine workings” for the specialty Development of reservoir deposits.

The activity of the St. Petersburg Mining Institute from the first years of its existence was characterized by a close connection with production. A natural consequence of this was the participation of its students and professors in the creation of the coal industry in Donbass, developing and deepening as the development of this industry.

To determine the place of rational location of field preparatory workings, the choice of type of fasteners, establishing technical conditions for its design and other practical issues must assess the stress state of the rock mass near these workings.

The stability of the mine workings is mainly determined by the size of the area of inelastic deformations formed in its vicinity. This region can be found computationally.

Rock emissions sharply reduce the rate and significantly increase the cost of excavation, create unfavorable conditions for mining operations at mines under construction.

Sedimentary rocks usually have a layered structure, and the strength characteristics at the contacts of layers (cohesion s_k and angle of internal friction φ_k ) can vary from zero to their values in the material of the layer (c_m and φ_m ).

At present, the development of minerals is carried out and designed at great depths. Practice shows that at depths of about 800 m the stability of mine workings significantly deteriorates. To predict their stability, it is necessary to comprehensively investigate the physical and mechanical properties of rocks, especially rheological properties, such as stress relaxation.

At present, considerable experience of experimental and theoretical studies on stress distribution around excavations of different cross-sectional shape has been accumulated. Most of these studies have been carried out in relation to workings with a smooth contour, however, it is known that the drilling and blasting method of sinking produces an uneven contour of the excavation. Technological irregularities formed in this process, and also occurring in some cases rock dumps, cause redistribution of stresses with the formation of zones of increased concentration. In full-scale conditions it is difficult to determine the value of stress concentration in these zones. Therefore, studies are usually carried out on models.

Practice shows that in ore mines, where for stripping of useful minerals are used mass explosions, the maintenance of mine workings causes significant difficulties, which with increasing depth of development increases.

Structural weakening of rocks is currently studied in different aspects. The diversity of the tasks involved determines a large number of research methods. Most of them provide only an indirect assessment of the weakening of the massif and do not give quantitative dependencies of the influence of weakening of rocks on their strength and deformation characteristics in the conditions of natural occurrence.

The reliability level of a support or its component is determined by the numerical value of one or more reliability criteria, for example, the duration of the average time of failure-free operation, or the probability of failure-free operation for a certain period of time.

Ring and arch supports subjected to loads may fail either from insufficient strength or from insufficient stability, which is verified by determining the critical load causing loss of stability of the structure.

The stability of mine workings depends to a large extent on the shape of their cross-section and the corresponding outline of the support. However, this well-known position is often not taken into account, as a result of which the load-bearing capacity of the support is not fully utilized.

A four-hinged brace is a statically defined geometrically variable system with one degree of freedom. In ground structures, geometrically variable systems are almost never used due to their instability. Therefore, the construction mechanics does not provide a specific methodology for their calculation.

For the efficiency of metal locking rods, they are given an initial tension of about 3-4 tons. Reinforced concrete solid rods are usually installed without initial tension; and they work no less effectively than metal locking rods. Steel-polymer rods with locking plugs are installed with or without tension.

From flooded mine workings the regulated descent of water with a large hydrostatic head can be ensured at reliable determination of the size of the target left between the flooded mine workings and the face of the slipway, through which the water is planned to be discharged. To calculate the size of the pillar it is necessary to know the compressive strength of rocks, which is usually determined by samples at natural moisture.

It is known that the rocks in the sides of horizontal excavations are destroyed either by shearing on one or another sliding surface or by tearing off the near-contour zones of the massif on vertical surfaces. Fracture by shear is well explained from the position of the theory of limit equilibrium of a cohesive bulk medium. The second possible type of fracture - detachment of contour zones has no clear explanation.