Loss of stability of exposed rock in underground workings
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The stability of exposed rock in the reduced pressure zone is lost because of loss of frictional force in the rocks due to opening of cracks on the surface owing to the formation of tensile stresses around the surface.
Depending on the state of the rocks, their pressure in the side of the working (for example, from the roof) and consequently the required support reaction may vary over a wide range; for elastic deformations it varies from γH to 0; for nonelastic deformations and action of frictional forces it varies from P to 0 (P<γH); and if friction is lost it varies from 0 to the weight of the rocks in the core of an arch of height h (this weight may vary because h=f(kγH) where k is the coefficient of stress concentration).
To retain frictional forces in the rocks we need huge support resistance in a prop-type support in a preparatory working; if the support resistance is small, the frictional force on the contour of exposed rock may be lost, and this lets down the pressure of the deloaded rocks. This type of support is wasteful of material in comparison with bar supports and artificial strengthening (cementing, etc.).
KeywordsFrictional Force Rock Pressure Underground Working Roof Rock Abutment Pressure
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- 1.A. K. Sidorenko, “The coefficients of friction of rocks,” in: Improvement of the Technique and Technology of Mining [in Russian], No. 22, “Nedra,” Moscow (1964).Google Scholar
- 2.G. A. Katkov, “Stress distribution in supports of underground workings and the surrounding rocks,” in: Problems of Rock Pressure [in Russian], No. 13, Izd. SO AN SSSR, Novosibirsk (1962).Google Scholar
- 3.A. N. Stavrogin, “On the limiting states and deformations of rocks,” in: Rock Pressure [in Russian], No. 59, izd. VNIMI, Leningrad (1965).Google Scholar
- 4.B. V. Matveev, “Research on the rheological properties of rocks,” in: Rock Pressure [in Russian], No. 59, izd. VNIMI, Leningrad (1965).Google Scholar