Abstract
As the excavation depth of underground engineering increases, the influence of in situ stress on the blasting effect cannot be ignored. The large number of fractures in the natural rock mass, coupled with the in situ stress, significantly impacts the propagation of stress waves. In this research, a synthetic rock mass approach based on the UDEC grain-based model was employed to investigate crack propagation and coalescence during double-borehole blasting with a variety of fracture networks and in situ stress conditions. The effects of the buried depth, fracture geometric parameters (i.e., the length and intensity), blast parameters (i.e., the explosive charge and borehole spacing), and borehole layouts on blasting-induced rock fracturing were examined. The simulation results showed that for a low-density fracture network dominated by short fractures, the pre-existing fractures have little effect on the propagation of blasting-induced cracks. However, as the length or density of fractures increases, pre-existing fractures could restrain the blasting-induced radial crack propagation and enhance the rock fragmentation between the borehole and the pre-existing fracture. This effect gradually disappeared as the in situ stress increased. In addition, the mismatch between the centreline of double boreholes and the direction of high in situ stress could also affect the coalescence of cracks, especially in high-density fracture networks. Finally, the applicability of empty holes to improve the crack coalescence between boreholes in fractured rock was discussed. This study should be beneficial in understanding the blasting behaviour of deep fractured rocks.
Article Highlights
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1.
The synthetic rock mass method was used to examine the crack coalescence process of double-borehole blasting.
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2.
The effects of the buried depth, fracture geometric parameters, blast parameters, and borehole layouts on blasting-induced rock fractures were investigated.
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3.
The applicability of empty holes to improve the crack coalescence between boreholes in fractured rock was discussed.
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- \(k_{n}\) :
-
Normal stiffness
- \(k_{s}\) :
-
Shear stiffness
- \(\Delta u_{n}\) :
-
Normal displacement increment
- \(\Delta u_{s}^{e}\) :
-
Elastic shear displacement increment
- \(\Delta \sigma_{n}\) :
-
Effective normal stress increment
- \(\Delta \tau_{s}\) :
-
Effective shear stress increment
- \(\tau_{s}\) :
-
Shear stress
- \(\tau_{\max }\) :
-
Peak shear strength
- \(\tau_{r}\) :
-
Residual shear strength
- c :
-
Cohesion
- \(c_{r}\) :
-
Residual cohesion
- \(\phi\) :
-
Friction angle
- \(\phi_{r}\) :
-
Residual friction angle
- α :
-
Proportionality coefficient
- a :
-
Fracture length exponent.
- P 21 :
-
Areal fracture intensity
- \(\sigma_{v}\) :
-
Vertical stress
- \(\sigma_{h}\) :
-
Horizontal stress
- \(\sigma_{h\max }\) :
-
Maximum horizontal principal stress
- \(\sigma_{h\min }\) :
-
Minimum horizontal principal stress
- \(\gamma\) :
-
Bulk density of the rock mass
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Acknowledgements
This work is financially supported by the National Natural Science Foundation of China (Grant No. 11802058, 41831281) and the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences (Grant No. Z018010). The valuable discussions with Prof. Jianchun Li at Southeast University throughout this study are gratefully acknowledged.
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Li, X., Pan, C., Li, X. et al. Application of a synthetic rock mass approach to the simulation of blasting-induced crack propagation and coalescence in deep fractured rock. Geomech. Geophys. Geo-energ. Geo-resour. 8, 57 (2022). https://doi.org/10.1007/s40948-022-00376-4
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DOI: https://doi.org/10.1007/s40948-022-00376-4