Rock Blasting Crack Propagation and Dynamic Response of Adjacent Roadway Structure under Active Confining Pressure

doi:10.12382/bgxb.2023.1089

Abstract

Abstract:

In order to study the failure process of rock blasting and adjacent roadway under confining pressure, the rock rectangular plate specimen with blast hole and roadway structure is tested, and the dynamic damage process of rock is obtained by using dynamic testing technology and high-speed camera method. A rock model containing roadway and single blasting hole is established based on Holmquist-Johnson-Cook (HJC) constitutive model. The simulated results without confining pressure are compared with the test results, and the feasibility of the numerical simulation method is verified. The stress initialization method is introduced into a finite element simulation platform to simulate the rock failure process under confining pressure, and the influences of different confining pressure environments on the rock blasting crack growth and the influence of partial confining pressure coefficient (k) on the failure process of roadway structure are analyzed. The results show that, under the condition of bidirectional constant confining pressure, the inhibition effect on crack is more significant and the protection effect on roadway is better with the increase in confining pressure level. Under the condition of unidirectional confining pressure, the roadway is damaged more seriously with the increase in horizontal confining pressure, and the roadway is less prone to failure with the increase in vertical confining pressure. Under the condition of partial confining pressure, the confining pressure has obvious guiding effect on the propagation of explosive crack, and the crack will expand in the direction of the principal stress. With the increase in confining pressure, the conductivity of crack is more significant. For partial confining pressure coefficient k<1, the cracks mainly spread in the vertical direction, and the roadway does not fail. For k>1, the greater the damage degree of the left spandrel of blasting face of roadway is with the increase in k, the worse the stability of the roadway is.

Key words: rock blasting, confining pressure, engineering blasting, roadway protection

CLC Number:

O382.2

MAO Xiang, HE Chenglong, CHEN Dayong, YANG Kexu, HUO Ziyi. Rock Blasting Crack Propagation and Dynamic Response of Adjacent Roadway Structure under Active Confining Pressure[J]. Acta Armamentarii, 2024, 45(12): 4323-4338.

Figures/Tables 31

Fig.1 Schematic diagram of specimen and borehole location

Fig.2 Arrangement of high-speed camera

Fig.3 Schematic diagram of experiment

Fig.4 Structure of 5# detonating cord

Fig.5 Schematic diagram of the trigger signal from the 8# military detonater

Fig.6 Propagation path of reflected stress wave in the model

Fig.7 Geometric diagram

Fig.8 Finite element model

Table 1 HJC model parameters[20-21]

参数	数值	参数	数值
ρ/(kg·m^-3)	3020	D₁	0.04
f_c/MPa	120	D₂	1.0
A	0.28	p_crush/MPa	40
B	2.5	p_lock/GPa	1.2
C	0.00186	μ_lock	0.002
N	0.79	EF_min	0.01
S_max	5	FS	0.035
G/GPa	28.7	K₁/GPa	12
T/MPa	8	K₂/GPa	25
μ_crush	0.0075	K₃/GPa	42

Table 2 Material parameters of explosive

参数	数值	参数	数值
ρ/(kg·m^-3)	1000	R₁	4.15
D/m·s^-1	6000	R₂	0.95
p_cj/GPa	21	ω	0.3
A/GPa	371	E₀/GPa	7
B/GPa	3.23	V₀	1.0

Table 3 Material parameters of air

参数	数值	参数	数值
ρ/(kg·m^-3)	1.29	C₄	0.4
C₀/MPa	0	C₅	0.4
C₁	0	C₆	0
C₂	0	E₀/(MJ·m^-3)	0.25
C₃	0	V_a	1.0

Table 4 Different partial confining pressure loading conditions

工况	p_h/MPa	p_v/MPa	k
1	0	0
2	5	5	1
3	10	10	1
4	15	15	1
5	5	0
6	10	0
7	15	0
8	0	5	0
9	0	10	0
10	0	15	0
11	15	2.5	6
12	15	5	3
13	15	7.5	2
14	7.5	15	0.5

Fig.9 Dynamic failure process of rock

Fig.10 Experimental result

Fig.11 Comparison of simulated and experimental results

Fig.12 Crack propagation without confining pressure

Fig.13 von Mises stress distribution about rock for k=1 and pv=5MPa

Table 5 Stress nephogram of rock under bidirectional constant confining pressure

Fig.14 Variation of crack length with time under different isotropic confining pressures

Fig.15 Crack growth under isotropic confining pressure(t=100μs)

Fig.16 Stress distribution of rock for pv=5MPa, 10MPa and 15MPa

Fig.17 Crack growth under vertical confining pressure loading

Fig.18 Stress distribution of rock for ph=5MPa, 10MPa and 15MPa

Fig.19 Crack growth under horizontal confining pressure loading

Fig.20 Stress distribution of rock for k=2, 3 and 6

Table 6 Rock stress nephogram under different partial confining pressure coefficients

Fig.21 Crack growth under different partial confining pressures

Fig.22 The ratio of long axis to short axis of elloptic crack distribution changing with k

Fig.23 Layout of detection point

Fig.24 Circumferential stresses at detection point for different k

Fig.25 Circumferential stress at point F under different k

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