Stress in the solid rock during firing of charges with oval cross section
When oval-sectioned charges are fired, the stresses produced in the solid rock are distributed nonuniformly, the nonuniformity increasing markedly with increasing ratio of the semiaxes of the ellipse.
The maximum tensile stresses produced by firing oval charges are greater than for circular charges, both near the powder chamber and at a considerable distance.
Near the powder chamber, the maximum tensile stresses appear at points on the major axis projected (with θ=0°); with increasing distance from the chamber these points are displaced, somewhat towards points on the minor axis projected.
Near the powder chamber the maximum tangential stresses also appear at points on the major axis projected (with θ=0°), but with increasing distance from the chamber the maximum is rapidly displaced towards points on the minor semiaxis projected (θ=90°)
Since nonuniformity of stress distribution is a very important factor in the fracture of rocks under dynamic loads, and since the maximum tensile stresses appear at the same distance from the powder chamber, we should expect a greater volume of fracturing from oval charges than from circular charges of equal weight. Experiments by the authors of [1, 2] have shown that the volume of rock fractured by oval charges increases with the ratio of the length of the charge to its cross-sectional width.
KeywordsElasticity Theory Hard Rock Maximum Tensile Stress Solid Rock Maximum Tangential Stress
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- 1.G. I. Tolkushev, G. S. Shcherbak, and A. A. Ansanbaev, The effect produced by using flat charges [in Russian], Izd. AN KazSSR, seriya gorn, dela, No. 2 (15) (1961).Google Scholar
- 2.G. I. Tolkushev, G. S. Shcherbak, and A. A. Ansanbaev, Influence of the powderchambershape on the shotfiring effect. Symposium: The Mining Industry of Kazakhstan [in Russian], Alma-Ata, Izd. AN KazSSR, No. 6 (1960).Google Scholar
- 3.Sh. G. Gamsakhurdiya, Method of breaking minerals by flat charges. Symposium: Shotfiring [in Russian], Moscow, Gosgortekhizdat, No. 50/7 (1962).Google Scholar
- 4.J. S. Reinhardt and J. Pearson, The Behavior of Metals under Impulse Loads [Russian translation], Moscow, Izd. inostr. lit. (1958).Google Scholar
- 5.V. N. Rodionov, Improving Shotfiring Performance in a Solid Medium [in Russian], Izd., IGD im. A. A. Skochinskogo (1961).Google Scholar
- 6.Strip Mining Technique Abroad [in Russian], Moscow, Gosgortekhizdat (1962).Google Scholar
- 7.F. A. Belaenko, Study of stress fields and fissure formation during firing of column charges in hard rocks. Symposium: Problems of Rock Fracturing Theory [in Russian], Moscow, Ugletekhizdat (1958).Google Scholar
- 8.G. I. Pokrovskii and I. S. Fedorov, The Effect of Impact and Explosion in Deformable Media [in Russian], Moscow, Promizdat (1957).Google Scholar
- 9.V. K. Filippov, Fracturing of brittle materials at different load application velocities. Proc. Inst. of Mining of the Kazakh Academy of Sciences,8 (1961).Google Scholar
- 10.A. V. Brezhnev, Applicability of elasticity theory for determining stresses produced in rocks by a drill. Collection: Papers of the Kazan' Mining-Metallurgical Inst. [in Russian], Moscow, Metallurgizdat, No. 20 (1959).Google Scholar
- 11.L. A. Shreiner, Physical Bases of Rock Mechanics [in Russian], Moscow, Gostoptekhizdat (1950).Google Scholar
- 12.A. Nadai, Plasticity and Fracturing of Solids [Russian translation], Moscow, Izd. inostr. lit. (1954).Google Scholar
- 13.D. W. Philips, Tectonics of mining, Colliery Engng. (August, 1948).Google Scholar
- 14.G. M. Lyakhov, Fundamentals of the Dynamics of an Explosion in the Ground and in Liquid Media [in Russian], Moscow, Izd. “Nedra” (1964).Google Scholar
- 15.V. K. Filippov, Experimental study of fracture of hard rocks by elongated charges parallel to the exposed surface. Symposium: Problems of Rock Crushing by an Explosion [in Russian], Moscow, Ugletekhizdat (1959).Google Scholar
- 16.N. L. Muskhelishvilli, Some Basic Problems in the Mathematical Theory of Elasticity [in Russian], Moscow, Izd. AN SSSR (1949).Google Scholar