Research on Blasting Mechanism of “Pin”-Shaped Slotting Without Raise in Sublevel Stope

doi:10.12068/j.issn.1005-3026.2024.11.012

Abstract

Abstract:

To response to high difficulty and cost in the blasting operation for cutting vertical slots in sublevel stope， a mine in Shandong as the engineering background is used to conduct research on the blasting mechanism of the “pin”?shaped slotting without raise in sublevel stope. The LS-DYNA numerical simulation method is employed to analyze the differences between the “pin”?shaped without raise cutting blasting and the VCR method cutting blasting. The study reveals the multi?free?surface effect of the “pin”?shaped blasting for slot cutting. The numerical results show that under the combined action of lateral and bottom free surfaces， the blasting stress distribution of the cylindrical blastholes in the “pin”?shaped without raise cutting blasting method is more uniform along their length， enhancing the rock?breaking capability at the free surfaces， reducing damage to the unexploded area， and improving the utilization of blasting energy. Through comprehensive comparison， the overbreak rate of the “pin”?shaped without raise cutting blasting method is reduced by 23.2%， the effective rock?breaking stress is increased by 12 MPa， and the vibration values of the surrounding rock in the unexploded area are reduced by 16.7%， significantly improving the blasting effect of slot cutting in sublevel stope.

Key words: sublevel stope, slot blasting, free face, equivalent stress, blasting vibration

CLC Number:

TD 235

Long AN, Lin HAN, Zhi WANG, Xing SUN. Research on Blasting Mechanism of “Pin”-Shaped Slotting Without Raise in Sublevel Stope[J]. Journal of Northeastern University(Natural Science), 2024, 45(11): 1612-1620.

Figures/Tables 23

Fig.1 Method of cutting and slotting without raise

Fig.2 Cutting and slotting method of “pin” shaped without raise

Fig.3 Layout of the holes for the “pin”?shaped blasting slotting method

Fig.4 Blasting sequence of “pin”?shaped blasting slotting

Fig.5 Blasting sequence for method of cutting and slotting without raise

Fig.6 Schematic diagram of the LS-DYNA numerical model

Table 1 Parameters of HJC model

ρ₀/(kg·m^-3)	G/MPa	σ_c/MPa	A	B	C	N	T/MPa	P_C	μ_c	p₁/MPa	μ₁	K₁/GPa	K₂/GPa	K₃/GPa
2 700	24 929.7	126.67	0.55	1.77	0.009 7	0.77	4.25	17	0.002 53	2 500	0.38	3.1	6	8.4

Table 2 Parameters of explosive material

ρ_e/(kg·m^-3)	v/（m·s^-1）	P_cj/GPa	A/GPa	B/GPa	R₁	R₂	E₀/(MJ·m^-3)	V₀	ω
1 150	5 122	9.53	276.2	8.44	5.199	2.099	3 870	1.0	0.5

Table 3 Parameters of air

ρ_a/(kg·m^-3)	C₀	C₁	C₂	C₃	C₄	C₅	C₆	V₀
1.29	0	0	0	0	0.4	0.4	0	1.0

Fig.7 Failure zone of numerical simulation

Fig.8 Equivalent depth of over excavation

Fig.9 Superposition nephogram of blasting stress

Fig.10 Blasting stress nephogram of cutting and slotting without raise

Fig.11 Blasting stress nephogram of “pin” shaped

Fig.12 Layout of the supervision points

Fig.13 Comparison of equivalent stress peaks on bottom free surface

Fig.14 Comparison of stress peaks on free surface

Fig.15 Comparison of peak stress of expected blasting boundary

Fig.16 Velocity distribution of particle on bottom free surface

Fig.17 Velocity distribution of particle on lateral free surface

Fig.18 Vibration velocity of supervision point on free surface

Fig.19 Blasting vibration velocity of design blasting boundary

Fig.20 Field slotting blasting effect

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