Long-period delay loosening blasting in open pit mines

The article discusses enhancement of loosening blasting with longer periods of delay between blasts in hard rocks. In recent decades scientists and practitioners in blasting have agreed on two-stage mechanism of rock fracture under blast load. At the first stage of volumetric pre-fracture, stress waves from blasts subject rocks to compression and tension, and microand macro-cracks and other defects appear, accumulate and concentrate in rocks. At the second stage of post-fracture, cracks coalesce into larger fractures of dominant destructive nature, the local growth of some cracks results in jointing. The mechanical action of blasting consists both in near-field shattering and in far-field weakening of rocks. Rocks in the far field alter their strength and fracture characteristics and drop into a new pre-fractured state. It is found that cracks grow in length by 10 mm in one compression–tension cycle, which is phenomenologically interpreted as pre-fracture of rocks. Longer periods of delay between blasts enable more frequent effect of the compression–tension cycles, with accumulation of cracks, which is favorable for coalescence of cracks and gradually reduces the size of blocks.

Shevkun E. B., Leshchinskiy A. V., Lysak Yu.A., Plotnikov A. Yu. Long-period delay loosening blasting in open pit mines. MIAB. Mining Inf. Anal. Bull. 2020;(10):29-41. [In Russ]. DOI: 10.25018/0236-1493-2020-10-0-29-41.

E.B. Shevkun¹, Dr. Sci. (Eng.), Professor,
A.V. Leshchinskiy¹, Dr. Sci. (Eng.), Assistant Professor, Professor, e-mail: 000399@pnu.edu.ru,
Yu.A. Lysak², General Director,
A.Yu. Plotnikov², Deputy Chief Engineer,
¹ Pacific National University, 680035, Khabarovsk, Russia,
² AVT-Amur LLC, Blagoveshchensk, Russia.

A.V. Leshchinskiy, e-mail: 000399@pnu.edu.ru.

1. Kutuzov B. N. etc. Spravochnik vzryvnika [The reference book of the detonator], Moscow, Nedra, 1988, 511 p.

2. Karkashadze G. G., Larionov P. V., Mishin P. N. Modeling crack growth under the action of cyclic loading. MIAB. Mining Inf. Anal. Bull. 2011, no 3, pp. 258—262.

3. Kryukov G. M., Glazkov Yu. V. Theoretical assessment of the degree of explosive crushing of rocks in quarries with different methods of initiating charges. MIAB. Mining Inf. Anal. Bull. 2003. Special edition 8, 26 p.

4. Drukovanyy M. F. Metody upravleniya vzryvom na kar'erakh [Explosion control methods in quarries], Moscow, Nedra, 1973, 416 p.

5. Shevkun E. B., Leshchinsky A. V., Dobrovolsky A. I., Galimyanov A.A. Patent RU 2593285, MPK F42D 1/08. 10.08.2016.

6. Lapshov A.A. Optimizatsiya intervalov zamedleniy pri massovykh vzryvakh na kar'erakh [Optimization of the intervals of decelerations during mass explosions in open pits], Candidate’s thesis, Ekaterinburg, 2011, 16 p.

7. Lupiy S. M. Prefracture zones during the blasting method of mine workings and their influence on the parameters of anchor fastening. Vzryvnoe delo. 2016, no 115/72, pp. 226— 232.

8. Skryabin R. M., Fedorov L. N. New approaches to the organization of resource-saving processes of rock destruction. MIAB. Mining Inf. Anal. Bull. 1995, no 5, pp. 59—62.

9. Adushkin V. V., Oparin V. N. From the phenomenon of alternating rock reaction to dynamic effects — to the waves of the pendulum type in tense geomedia. Part I. Fiziko-tekhnicheskiye problemy razrabotki poleznykh iskopayemykh. 2012, no 2, pp. 3—27.

10. Kurlenya M. V., Oparin V. N., Revuzhenko A. F., Shemyakin E. I. About some features of the reaction of rocks to explosive effects in the near zone. Doklady Akademii nauk SSSR. 1987. vol. 293, no 1.

11. Kurlenya M. V. The alternating reaction of rocks to a dynamic effect. Doklady Akademii nauk SSSR. 1992, vol. 323, no 2.

12. Sadovsky M.A., Adushkin V. V., Spivak A.A. About the size of zones of irreversible deformation during an explosion in a block medium. Izvestiya Akademii nauk SSSR. Fizika Zemli. 1989, no 9, pp. 109—115.

13. Kurlenya M. V., Oparin V. N. Skvazhinnye geofizicheskie metody diagnostiki i kontrolya napryazhenno-deformirovannogo sostoyaniya massivov gornykh porod [Well logging methods for the diagnosis and control of the stress-strain state of rock masses], Novosibirsk, Nauka, 1999, 335 p.

14. Rodionov V. N. Mekhanicheskiy effekt podzemnogo vzryva [The mechanical effect of an underground explosion], Moscow, Nedra, 1971, 222 p.

15. Nikiforovskiy V. S., Shemyakin E. I. Dinamicheskoe razrushenie tverdykh tel [Dynamic destruction of solids], Novosibirsk, Nauka, 1979, 272 p.

16. Mityushkin Yu.A. Optimization of the parameters of blasting operations by increasing the intervals of deceleration. MIAB. Mining Inf. Anal. Bull. 2015, no 4, pp. 341—348.

17. Shevkun E. B., Leshchinsky A. V., Lysak Yu. A., Plotnikov A. Yu. Features of explosive loosening at prolonged intervals of deceleration. MIAB. Mining Inf. Anal. Bull. 2017, no 4, pp. 272—282.

18. Yurovskikh A. V. Razrabotka modeli razrusheniya gornykh porod na kvazistaticheskoy stadii deystviya vzryva [Development of a model of rock destruction at the quasistatic stage of the explosion], Candidate’s thesis, Saint-Petersburg, 2003, 119 p.

19. Kochanov A. N., Odintsev V. N. Theoretical estimation of the radius of the region of prefracture of rocks in a camouflage explosion. Vzryvnoe delo. 2015, no 113/70, pp. 41—54.

20. Baron V. L., Kantor V. Kh. Tekhnika i tekhnologiya vzryvnykh rabot v SShA [Technique and technology of blasting in the USA], Moscow, Nedra, 1989, 376 p.

21. Khopunov E.A. Selektivnoe razrushenie mineral'nogo i tekhnogennogo syr'ya (v obogashchenii i metallurgii) [Selective destruction of mineral and technogenic raw materials (in enrichment and metallurgy)], Ekaterinburg, OOO «UIPTS», 2013, 429 p.

22. Khalkachev R. K., Khalkachev K. V. Fracture selectivity control during crushing and grinding of rocks based on similarity and dimension methods in crack dynamics. Gornyi Zhurnal. 2016, no 6, pp. 64—66.

23. Momeni A., Karakus M., Khanlari G. R., Heidari M. Effects of cyclic loading on the mechanical properties of a granite. International Journal of Rock Mechanics and Mining Sciences. 2015. Vol. 77, Pp. 89—96.

24. Xiaodong Fu, Qian Sheng, Yonghui Zhang, Jian Chen Application of the discontinuous deformation analysis method to stress wave propagation through a one-dimensional rock mass. International Journal of Rock Mechanics and Mining Sciences. 2015. Vol. 80. Pp. 155—170.

25. Аkаndе J. М., Lawal А. I. Optimization of blasting parameters using regression models in ratcon and NSCE granite quarries. Ibadan, Оуо State, Nigeria. Geomaterials. 2013. Vol. 3. No 1. Рp. 28—37. DOI: 10.4236/gm.2013.31004.

26. Haeri H., Shahriar K., Fatehi Marji M., Moarefvand P. Experimental and numerical study of crack propagation and coalescence in precracked rock-like discs. International Journal of Rock Mechanics and Mining Sciences. 2014. Vol. 67. Pp. 20—28.

27. Liu T., Cao P., Lin H. Damage and fracture evolution of hydraulic in compression-shear rock cracks. Theoretical and Applied Fracture Mechanics. 2014. Vol. 74. Pp. 55—63. [In Russ].