Assessment of near-field blast effect toward optimized drilling-and-blasting in pit wall rock mass

The article presents the scientific research findings on the effect of a borehole charge blast in the near field. The detailed analysis of pit wall damages under massive blasting is performed depending on the rock fracture mechanism. It is found that basic factors to contribute to initiation and opening of fractures in the near field are the high peak particle velocities and post-limiting pressure of gaseous products of explosive detonation. The experimental blasts are described in detail and implemented. The aim of the experimental blasting was to measure PPV directly in rock mass, in the near field of a blasthole charge, and to determine the permeability factor of a separatory slot. The measurement results were processed and analyzed using the Sweden model Holmberg & Persson which allows interpreting and estimating PPV at any point of rock masses. Alongside with PPV, the permeability factor of a separatory slot was determined, which ranged as 52 to 61 % depending on the distance to the slot and on the explosive charge design. The obtained value is reflective of the good quality of cut-back in the pit. The fracture modeling has shown that H & P model is conservative and overestimates the actual level of vibrations. Despite the shortcomings, the model is applicable in drilling-and-blasting pattern design though it needs some calibration using the real-life criteria of rock fracture under the dynamic impact of borehole charge blasting.

Alenichev I.A., Rakhmanov R.A., Shubin I. L. Assessment of near-field blast effect toward optimized drilling-and-blasting in pit wall rock mass. MIAB. Mining Inf. Anal. Bull. 2020;(4):85-95. [In Russ]. DOI: 10.25018/0236-1493-2020-4-0-85-95.

I.A. Alenichev, Cand. Sci. (Eng.), Leading Engineer for Drilling and Blasting, LLC «Polyus Project», 660028, Krasnoyarsk, Russia, e-mail: AlenichevIA@polyusgold.com,
R.A. Rakhmanov, Cand. Sci. (Eng.), Senior Drill and Blast Manager, UK Polyus LLC, 123056, Moscow, Russia, e-mail: RakhmanovRA@polyusgold.com,
I.L. Shubin, Technical Manager (Europe/CIS/N-W Africa), JSC «Davey Bickford Enaex», Russia, e-mail: igor.shubin@daveybickfordenaex.com.

I.A. Alenichev, e-mail: AlenichevIA@polyusgold.com.

1. Fokin V.A. Proektirovanie i proizvodstve burovzryvnykh rabot pri postanovke ustupov v konechnoe polozhenie na predel'nom konture glubokikh kar'erov [Designing and implementation of drilling and blasting operations during final sloping of benches in deep pits], Apatity, KNTS RAN, 2004, 133 p.

2. Alenichev I.A. Rock mass response to dynamic effect of blasting in the area of open pit mine. Gornyy informatsionno-analiticheskiy byulleten’. 2018, no 7, pp. 189–195. [In Russ]. DOI: 10.25018/0236-1493-2018-7-0-189-195.

3. Rorke A. J. Limiting blast-induced damage on final pit walls, available at: https://www. agg-net.com/resources/articles/drilling-blasting/limiting-blast-induced-damage-on-final-pitwalls, 2011.

4. Fokin V.A. Metodicheskie aspekty analiza tekhnologicheskoy informatsii pri proizvodstve burovzryvnykh rabot v usloviyakh kar'erov [Methodic aspects of analyzing technological information during drilling-and-blasting operations in open-pits], Apatity, KNTS RAN, 2015, 133 p.

5. Belin V.A., Kholodilov A. N., Gospodarikov A. P. Procedural framework for prediction of seismic effect of massive blasting. Gornyy zhurnal. 2017, no 2, pp. 66—68. [In Russ].

6. Goswami T., Jeric S., Brent G. Holistic scientific approach to address wall damage and berm loss from blasting in large open cut metal mines. International Society of Explosives Engineers, 2011.

7. Kozyrev S.A., Alenichev I.A., Kamyanskiy V. N., Sokolov A. V. Features of seismic presplitting blasting action on the out-contour rock and methods of its reduction under the conditions of «Iron» open pit mining on the Kovdorsky Processing Plant. Vzryvnoe delo. 2017, no 118/75, pp. 212—226. [In Russ].

8. Bersenev G. P., Krapivina I. S., Strovskiy V. E. Effective measures reduce the influence of seismology of explosion during constructive excavation in constrained environment. Izvestiya vysshikh uchebnykh zavedeniy. Gornyy zhurnal. 2014, no 1, pp. 114—117. [In Russ].

9. Dindarloo S. R. Design of controlled blasting (pre-splitting) in Golegohar iron ore mine, Iran. Transactions of the Institution of Mining and Metallurgy, Section A: Mining Technology, 2015, Vol. 124, No 1, Pp. 64—68. DOI: 10.1179/1743286314Y.0000000077.

10. Holmberg R., Persson P-A. The Swedish approach to contour blasting. Proceedings of the 4th Conference on Explosives and Blasting Technique, Society of Explosives Engineers, New Orleans, Louisiana, 10—15 February, 1978, pp. 113—127.

11. Tannant D. D., Peterson J. Evolution of blasting practices at the EkatiTM diamond mine.

17th International Mining Congress and Exhibition of Turkey (IMCET2001), 2001, pp. 297—304.

12. Hustrulid W. А. Blasting principles for open pit mining. Vol. 1, 1999, 382 p.

13. Shrey A., Kaushik D. Estimation of near-field peak particle velocity. A mathematical model. Journal of Geology and Mining Research, 2010, Vol. 2, No 4, Pp. 68–73.

14. Shuyfer M. I., Azarkovich A. E. Calculation of fracturing zone size under blasting of borehole charges in strong rock masses. Vzryvnoe delo. 1980, no 82/39, pp. 191—209. [In Russ].

15. McKenzie C. K. Blasting near open pit walls. APSSIM, 2016, pp. 83—94.

16. Battison R., Esen S., Duggan R. et al. Reducing crest loss at Barrick Cowal gold mine. Proceedings of the 11th International Symposium on Rock Fragmentation by Blasting, Sydney, NSW, 24–26 August 2015, pp. 1—14.

17. Borovikov V.A., Vanyagin I. F. Tekhnika i tekhnologiya vzryvnykh rabot. Uchebnoe posobie [Blasting technology and equipment. Educational aid], Leningrad, Izd-vo LGI, 1985, 89 p.

18. Blair D. P., Minchinton A. Near-field blast vibration models. Fragblast, 2006, No 8, pp. 152—159.

19. Müller B., Hausmann J., Niedzwiedz H. Prediction and minimisation of vibrations during production blasts. Fragblast, 2009, No 9, pp. 47—55.

20. Silva J., Worsey T., Lusk B. Practical assessment of rock damage due to blasting. International Journal of Mining Science and Technology, 2018. Vol. 29, No 3. Pp. 379—385. DOI: 10.1016/j.ijmst.2018.11.003. [In Russ].