Under the stability of mine workings is understood the preservation within a given period of time the required size and shape of its cross-section in accordance with the requirements of the rules of technical operation and safety. ...

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 ).

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.

Wooden rods, which usually have a wedge-slot construction and possess low weight, low cost, ease of manufacture, non-deficiency of material, are rarely used. The reasons for this are the low bearing capacity of the deep lock of such rods, not exceeding 1 -1,5 tons, short life and low resistance to shear forces...

According to the current temporary instruction, it is recommended to use the rod fastening only in rocks of strength not lower than 3 (on the scale of M. M. Protodyakonov).According to preliminary calculations, the use of rod fastening in the drifts through thick coal seams, in particular, at the Kuzbass hydro-mines, should give a significant technical and economic effect. Since the coal strength factor of thick coal seams often does not exceed 0.3-0.5, and the coal mass is characterized by significant fracturing, it was necessary to justify the possibility of using the rod support in difficult conditions. In this connection it was necessary to reveal the character of deformation of weak fractured coal near the mine workings, secured with rod fasteners at different dip angles of seams ...

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 application of rod support to combat rock heave in mine workings in Donbass mines has shown that conventional rod locks do not provide reliable anchoring in clayey rocks. Their pull-out forces during tests did not exceed 1–1.5 tons, which is completely insufficient for metal rods. Therefore, to combat clay heave in workings of mines in the Moscow Basin, the authors have proposed a metal tubular rod support.

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).