Rock fracture mechanism of buffer blasting with cushion layer at the borehole bottom

Abstract

This study primarily investigates the rock fracture mechanism of bottom cushion layer blasting and explores the effects of the bottom cushion layer on rock fragmentation. It involves analyses of the evolution patterns of blasting stress, characteristics of crack distribution, and rock fracture features in the specimens. First, blasting model experiments were carried out using the dynamic caustics principle to investigate the influence of bottom cushion layers and initiation methods on the integrity of the bottom rock mass. The experimental results indicate that the combined use of bottom cushion layers and inverse initiation effectively protects the integrity of the bottom rock mass. Subsequently, the process of stress wave propagation and dynamic crack propagation in rocks was simulated using the continuum–discontinuum element method (CDEM) and the Landau explosion source model, with varying thicknesses of bottom cushion layers. The numerical simulation results indicate that with increasing cushion thickness, the absorption of energy generated by the explosion becomes more pronounced, resulting in fewer cracks in the bottom rock mass. This illustrates the positive role of the cushion layer in protecting the integrity of the bottom rock mass.

Keywords

bottom cushion layer / blasting / crack propagation / continuum–discontinuum element method / dynamic stress intensity factor

References

[1] Zhang ZX, Sanchidrián JA, Ouchterlony F, Luukkan-en S. Reduction of fragment size from mining to mineral processing: A review. Rock Mech. Rock Eng.. 2023, 56(1): 747

[2] Xu P, Yang RS, Zuo JJ, et al. . Research progress of the fundamental theory and technology of rock blasting. Int. J. Miner. Metall. Mater.. 2022, 29(4): 705

[3] Ren FY, Sow TAM, He RX, Liu XR. Optimization and application of blasting parameters based on the “pushing-wall” mechanism. Int. J. Miner. Metall. Mater.. 2012, 19(10): 879

[4] Wu HJ, Gong M, Yang RS, Wu XD, Liu XY. Double-face intelligent hole position planning method for precision blasting in roadways using a computer-controlled drill jumbo. Int. J. Miner. Metall. Mater.. 2023, 30(6): 1025

[5] Yao ZG, Tian QF, Fang Y, Ye LB, Pu S, Fang XF. Propagation and attenuation of blast vibration waves in closely spaced tunnels: A case study. Arabian J. Sci. Eng.. 2022, 47(4): 4239

[6] N. Kumar Bhagat, A.K. Mishra, R.K. Singh, C. Sawmliana, and P.K. Singh, Application of logistic regression, CART and random forest techniques in prediction of blast-induced slope failure during reconstruction of railway rock-cut slopes, Eng. Fail. Anal., 137(2022), art. No. 106230.

[7] Wu XX, Hu YG, Liu MS, Zhao G, Yang ZW. Research progress of blasting technology in hydropower engineering. J. Changjiang River Sci.c Res. Inst.. 2021, 38(10): 112

[8] Zhao JS, Chen BR, Jiang Q, et al. . Microseismic monitoring of rock mass fracture response to blasting excavation of large underground Caverns under high geostress. Rock Mech. Rock Eng.. 2022, 55(2): 733

[9] C.X. Ding, R.S. Yang, C. Chen, X.G. Zhu, C. Feng, and Q.M. Xie, Space-time effect of blasting stress wave and blasting gas on rock fracture based on a cavity charge structure, Int. J. Rock Mech. Min. Sci., 160(2022), art. No. 105238.

[10] Wang T, Ye WW, Liu LY, Liu K, Jiang NS, Feng XH. Disturbance failure mechanism of highly stressed rock in deep excavation: Current status and prospects. Int. J. Miner. Metall. Mater.. 2024, 31(4): 611

[11] Yang RS, Ding CX, Yang LY, Lei Z, Zhang ZR, Wang YB. Visualizing the blast-induced stress wave and blasting gas action effects using digital image correlation. Int. J. Rock Mech. Min. Sci.. 2018, 112: 47

[12] X.T. Liang, C.X. Ding, X.G. Zhu, J. Zhou, C. Chen, and X. Guo, Visualization study on stress evolution and crack propagation of jointed rock mass under blasting load, Eng. Fract. Mech., 296(2024), art. No. 109833.

[13] Yang RS, Zuo JJ, Ma LW, Zhao Y, Liu Z, Xie QM. Analysis of explosion wave interactions and rock breaking effects during dual initiation. Int. J. Miner. Metall. Mater.. 2024, 31(8): 1788

[14] Ding CX, Yang RS, Guo X, Sui Z, Xiao CL, Yang LY. Effects of the initiation position on the damage and fracture characteristics of linear-charge blasting in rock. Int. J. Miner. Metall. Mater.. 2024, 31(3): 443

[15] X.D. Li, K.W. Liu, Y.Y. Sha, J.C. Yang, and R.T. Song, Numerical investigation on rock fragmentation under decoupled charge blasting, Comput. Geotech., 157(2023), art. No. 105312.

[16] X.M. Lou, P. Zhou, J. Yu, and M.W. Sun, Analysis on the impact pressure on blast hole wall with radial air-decked charge based on shock tube theory, Soil Dyn. Earthquake Eng., 128(2020), art. No. 105905.

[17] Wu XD, Gong M, Wu HJ, Hu GF, Wang SJ. Vibration reduction technology and the mechanisms of surrounding rock damage from blasting in neighborhood tunnels with small clearance. Int. J. Min. Sci. Technol.. 2023, 33(5): 625

[18] Liu GX, Lu WB, Niu XQ, Wang GH, Chen M, Yan P. Excavation shaping and damage control technique for the breccia lava dam foundation at the Bai-he-tan hydropower station: A case study. Rock Mech. Rock Eng.. 2020, 53(4): 1889

[19] Huang L. Study on the Pliability Cushion Explosion Method and Effectively of the Protected Level of Dam Foundation Rock’ Excavating. 2002, Wuhan, Wuhan University of Technology

[20] Zhang YZ, Lu WB, Chen M, Yan P, Hu YG. Dam foundation excavation techniques in China: A review. J. Rock Mech. Geotech. Eng.. 2013, 5(6): 460

[21] Wu XX, Zhao G, Zhang ZY, et al. . A study of the theory of duplicate cushion and its optimized design by comupter. Explos. Mater.. 2000, 4(4): 8

[22] H.R. Hu, W.B. Lu, P. Yan, M. Chen, and Q. Gao, A vibration-isolating blast technique with shock-reflection device for dam foundation excavation in complicated geological conditions, Shock Vib., 2018(2018), No. 1, art. No. 8029513.

[23] Hu HR, Lu WB, Yan P, Chen M, Gao QD, Yang ZW. A new horizontal rock dam foundation blasting technique with a shock-reflection device arranged at the bottom of vertical borehole. Eur. J. Environ. Civ. Eng.. 2020, 24(4): 481

[24] Lu WB, Hu HR, Yan P, Chen Y, Rong YJ, Wang ZL. Vertical borehole shock-reflection blasting technique and its application in foundation excavation. Chin. J. Rock Mech. Eng.. 2018, 37(S1): 3143

[25] Kutter HK, Fairhurst C. On the fracture process in blasting. Int. J. Rock Mech. Min. Sci. Geomech. Abstr.. 1971, 8(3): 181

[26] Rossmanith HP. Mechanics of Jointed and Faulted Rock. 1998, London, Routledge

[27] C.X. Ding, R.S. Yang, and L.Y. Yang, Experimental results of blast-induced cracking fractal characteristics and propagation behavior in deep rock mass, Int. J. Rock Mech. Min. Sci., 142(2021), art. No. 104772.

[28] Yang RS, Ding CX, Yang LY, Chen C. Model experiment on dynamic behavior of jointed rock mass under blasting at high-stress conditions. Tunnelling Underground Space Technol.. 2018, 74: 145

[29] Li SH, Zhao MH, Wang YN, Rao Y. A new numerical method for Dem–Block and particle model. Int. J. Rock Mech. Min. Sci.. 2004, 41(S1): 414

[30] Feng C, Li SH, Liu XY, Zhang YN. A semi-spring and semi-edge combined contact model in CDEM and its application to analysis of Jiweishan landslide. J. Rock Mech. Geotech. Eng.. 2014, 6(1): 26

RIGHTS & PERMISSIONS

University of Science and Technology Beijing