Effects of schistosity on rock fragmentation and associated energy dissipation under blasting

Abstract

Drilling and blasting in foliated rock masses widely occur in tunnel engineering and mining operations. However, the effects of schistosity on rock fragmentation and energy dissipation behavior remain insufficiently understood. This study first conducts schist blast testing to investigate the influences of schistosity characteristics on rock fragmentation pattern and fragment size distribution, utilizing image processing to analyze the variations in fragment shape and fracture energy dissipation. Finite element models of schist blasting are then developed to simulate the successive process of detonation-induced stress propagation, crack network evolution and rock fragmentation. Blast testing and following image analysis reveal that schist fragments exhibit pronounced foliated features, with many fragments displaying platy shapes, and the average aspect ratio of rock fragments is primarily concentrated in the range of 0.5–0.7. When the schistosity is perpendicular to borehole and the proportion of harder rock matrix increases, the mean fragment size increases, the uniformity of fragment size distribution reduces, and thus the rock fragmentation performs worse. The mean aspect ratio of fragments increases with rounder rock fragments. Compared to blasting with schistosity perpendicular to borehole, blasting with schistosity parallel to borehole consumes more explosive energy, with an average increase of 27.28% in blast testing. Numerical simulations demonstrate that during the propagation of stress waves in schist, cyclic reflections occur at schistosity planes, mainly resulting in fracture and breakage in the weaker rock matrix. This leads to blast-induced cracks growing parallel to schistosity planes at intervals, forming flattened rock fragments with relatively small aspect ratios. The current findings suggest that schistosity perpendicular and parallel to borehole is unfavorable and favorable for rock fragmentation, respectively. Thus, in blasting engineering practice with simple layered structures, aligning the borehole with the dominant schistosity direction is an effective strategy for optimizing rock fragmentation performance, particularly when the harder rock matrix constitutes a large proportion.

Keywords

Foliated rock blasting / Rock fragmentation / Energy dissipation / Image processing / Numerical modeling

References

[1] Li XB. Rock dynamic fundamentals and applications. Beijing: Science Press; 2014.

[2] Zhang ZX. Rock fracture and blasting: theory and applications. Oxford: B—H/Elsevier Science; 2016.

[3] Hu YG, Lu WB, Wu XX, Liu MS, Li P. Numerical and experimental investigation of blasting damage control of a high rock slope in a deep valley. Eng Geol 2018; 237:12-20.

[4] Lu Y, He BG, Li HP, Li Q, Ren C. Theoretical and numerical investigation of damage zones in deep tunnels within a layered rock mass under full—face blasting. Int J Rock Mech Min Sci 2025; 188:106053.

[5] Luo PK, Li DY, Zhou AH, Ma JY, Zhu QQ, Jiang JT. Influence of bedding plane on the tensile properties and crack propagation of soft and hard laminated rock—like under Brazilian test. Theor Appl Fract Mech 2023; 127:104087.

[6] Mei J, Zhang WZ, Xu BS, Zhu YX, Wang BK. Optimization methods of blasting parameters of large cross—section tunnel in horizontal layered rock mass. Geotech Geol Eng 2021; 39(7):5309—23.

[7] Banadaki MD. Stress—wave induced fracture in rock due to explosive action. Ph.D: University of Toronto, Canada; 2011.

[8] Yilmaz O, Unlu T. Three dimensional numerical rock damage analysis under blasting load. Tunn Undergr Space Technol 2013; 38:266-78.

[9] Zhang XT, Li ZB, Yu H, Zhou HM, Wang HL, Jiao XT, et al. Experimental and numerical studies on rock damage law in straight—hole cut blasting under biaxial confining pressure. Int J Min Sci Technol 2025; 35(9):1529-41.

[10] Guo PF, Zhang XY, Ye KK, Wang X, Huang M, Hu JZ, et al. Energy regulation mechanism and medium—filling effect of energy—focusing blast. Int J Min Sci Technol 2025; 35(5):767-81.

[11] Zhang H, Xing XY, Du YT, Li TC, Yu JX, Zhu QW. Adjustment mechanism of blasting dynamic—static action in the water decoupling charge. Int J Min Sci Technol 2024; 34(6):821—36.

[12] Ding XH, Ao ZC, Zhou W, Qin H, Yang ZA, An W, et al. Geopolymer—based modification of blasting sealing materials and optimization of blasting block size in coal seams of open pit mines. Int J Min Sci Technol 2023; 33(12):1551-62.

[13] Chi LY, Zhang ZX, Aalberg A, Li CC. Experimental investigation of blast—induced fractures in rock cylinders. Rock Mech Rock Eng 2019; 52(8):2569—84.

[14] Chi LY, Zhang ZX, Aalberg A, Yang J, Li CC. Fracture processes in granite blocks under blast loading. Rock Mech Rock Eng 2019; 52(3):853-68.

[15] Zhang ZX, Chi LY, Qiao Y, Hou DF. Fracture initiation, gas ejection, and strain waves measured on specimen surfaces in model rock blasting. Rock Mech Rock Eng 2021; 54(2):647—63.

[16] Zhang ZX, Qiao Y, Chi LY, Hou DF. Experimental study of rock fragmentation under different stemming conditions in model blasting. Int J Rock Mech Min Sci 2021; 143:104797.

[17] Zhang ZX, Chi LY, Zhang QB. Effect of specimen placement on model rock blasting. Rock Mech Rock Eng 2021; 54(8):3945—60.

[18] Li XD, Liu KW, Sha YY, Yang JC, Hong ZX. Numerical investigation on blast—induced rock fragmentation with different stemming structures. Geomech Geophys Geo Energy Geo Resour 2023; 9(1):112.

[19] Li XD, Liu KW, Sha YY, Yang JC, Song RT. Numerical investigation on rock fragmentation under decoupled charge blasting. Comput Geotech 2023; 157:105312.

[20] Yi CP, Johansson D, Greberg J. Effects of in—situ stresses on the fracturing of rock by blasting. Comput Geotech 2018; 104:321—30.

[21] Tao J, Yang XG, Li HT, Zhou JW, Fan G, Lu GD. Effects of in—situ stresses on dynamic rock responses under blast loading. Mech Mater 2020; 145:103374.

[22] Li XD, Liu KW, Yang JC, Song RT. Numerical study on blast—induced fragmentation in deep rock mass. Int J Impact Eng 2022; 170:104367.

[23] Yi CP, Sjöberg J, Johansson D. Numerical modelling for blast—induced fragmentation in sublevel caving mines. Tunn Undergr Space Technol 2017; 68:167-73.

[24] Tao J, Yang XG, Li HT, Zhou JW, Qi SC, Lu GD. Numerical investigation of blast—induced rock fragmentation. Comput Geotech 2020; 128:103846.

[25] Liu DQ, Wei D, Chen M, Zhang H, Lu WB. Prediction of the median fragmentation of bench blasting in layered rock mass based on discrete fracture network. Rock Mech Rock Eng 2024; 57(3):1653—68.

[26] Wang ZL, Konietzky H. Modelling of blast—induced fractures in jointed rock masses. Eng Fract Mech 2009; 76(12):1945—55.

[27] Dotto MS, Apel D, Pourrahimian Y. Investigating the influence of discontinuity parameters on blast—induced fragmentation. Int J Min Reclam Environ 2024; 38(9):745-69.

[28] Lin MJ, Li JL, Zhou JQ, Xiao DJ, Wu JM, Xue B. Study on welding parameters and interface of aluminum/steel composite pipe using underwater explosive welding. Weld World 2024; 68(11):3019-32.

[29] Hustrulid W. Underground mining methods: society for mining, metallurgy, and exploration, 2001.

[30] Hogan JD, Rogers RJ, Spray JG, Boonsue S. Dynamic fragmentation of granite for impact energies of 6—28J. Eng Fract Mech 2012; 79:103-25.

[31] Ouchterlony F. The Swebrec© function: linking fragmentation by blasting and crushing. Min Technol 2005; 114(1):29-44.

[32] Yang S, Ning JG, Xu XZ. Fragment theoretical model of concrete blocks subjected to blast loads. Int J Impact Eng 2023; 176:104562.

[33] China North Industries Group Corporation. WJ 2470—1997 Safety code for design of dangerous buildings with small amount of propellants, explosives and their products. 1998.

[34] Livermore Software Technology Corporation. LS—DYNA Keyword User’s Manual, Version R 8.0 2015.

[35] Zuo JJ, Yang RS, Gong M, Ma XM, Wang YB. Fracture characteristics of iron ore under uncoupled blast loading. Int J Min Sci Technol 2022; 32(4):657—67.

[36] Kucewicz M, Baranowski P, Mazurkiewicz Ł, Małachowski J. Comparison of selected blasting constitutive models for reproducing the dynamic fragmentation of rock. Int J Impact Eng 2023; 173:104484.

[37] Xie LX, Lu WB, Zhang QB, Jiang QH, Chen M, Zhao J. Analysis of damage mechanisms and optimization of cut blasting design under high in—situ stresses. Tunn Undergr Space Technol 2017; 66:19-33.

[38] Borrvall T, Riedel W. The RHT concrete model in LS—DYNA. In: Proceedings of the 8th European LS—DYNA user conference. p. 23-34.

[39] Liu KW, Li XD, Hao H, Li XB, Sha YY, Wang WH, et al. Study on the raising technique using one blast based on the combination of long—hole presplitting and vertical crater retreat multiple—deck shots. Int J Rock Mech Min Sci 2019; 113:41-58.

[40] Xiong YB, Wang CM, Zhao K. Experimental tests on constitutive relation of fine sand under high stress and quasi one—dimensional strain. Rock Soil Mech 2010;31:216-31.

[41] Wang WG, Chen YM, Liu HL, Zhang ZC. Numerical simulation of explosion in soil based on a coupled SPH—FEM algorithm. Rock Soil Mech 2013; 34(7):2104—10. in Chinese.

[42] Li HC. The study of the rock RHT model and to determine the values of main parameters. Beijing: China University of Mining and Technology; 2014.

[43] Li XD, Liu KW, Yang JC, Sha YY, Song RT. Numerical study on the effect of in—situ stress on smoothwall blasting in deep tunnelling. Undergr Space 2023; 11:96-115.