Available online at ScienceDirect. Procedia Engineering 84 (2014 )

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1 Available online at ScienceDirect Procedia Engineering 84 (2014 ) ISSST, 2014 International Symposium on Safety Science and Technology Study on attenuation law of open-pit bench blasting vibration ZHANG Yuanjuan a,b, * a College of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo , Henan, China b School of Safety Engineering, Henan Institute of Engineering, Zhengzhou , China Abstract In order to analyze attenuation law of the open-pit mine blasting vibration, the FEM program LS-DYNA is used to establish model of double millisecond holes in bench blasting, through the analysis of numerical simulation results, it can be obtained that peak particle velocityppvand energy attenuation are occurred near the blasting source, which provided basic theory for protection of buildings near blasting source Published The Authors. by Elsevier Published Ltd. by This Elsevier is an Ltd. open access article under the CC BY-NC-ND license ( Peer-review under responsibility of scientific committee of Beijing Institute of Technology. Peer-review under responsibility of scientific committee of Beijing Institute of Technology Keywords: blasting vibration; bench blasting; LS-DYNA; attenuation law 1. Introduction With the widespread application of blasting technology in open bench mine, the effect of blasting vibration caused by blasting to reserved slope and near construction of buildings has become one of the urgent problems to be solved, therefore, studying on attenuation law of blasting vibration of open bench mine blasting on the protection of explosion, which has an important significance for slope and building near the blasting source. According to the small experiment and project to obtain value of K and, attenuation formula with different conditions of change law are compared and analyzed[1], a modified formula which considered some factors, such as charge volume, blast center distance, altitude effect, free surface, etc. was proposed[2]. In this paper, using FEM program LS-DYNA to establish finite element model to analyze the open-pit bench millisecond blasting, from the peak particle velocity and the attenuation of blasting vibration to analyze the simulation result. * Corresponding author. Tel.: address: zyj_whut@163.com Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license ( Peer-review under responsibility of scientific committee of Beijing Institute of Technology doi:116/j.proeng

2 Zhang Yuanjuan / Procedia Engineering 84 (2014 ) Numerical simulation analysis 2.1. The calculation equation of state The state equation JWL is used[3-11], which set to describe explosive energetic material pressure characteristics and its expression is RV 1 R2V E0 P A(1 )e B(1 )e (1) RV 1 RV 2 V where V is volume change, A, B, ω, R 1, R 2, E 0 are the material constants. Rock parameters selection of numerical simulation is showed in Table 1. Table 1. Rock mechanics parameters used in the numerical calculation. Elastic modulus/ GPa Tangent modulus /GPa Yield stress /MPa Rock density /(kg.m -3 ) Poisson ratio Constitutive model According to the actual condition of open pit mine, numerical simulation model of millisecond blasting is established, the front aperture is 140mm, the back row aperture is 90mm, the hole depth is both 13m, the distance between two rows is 4m, ultra deep is both 1m, the bench height is 12m, the model high is 26m, the slope angle is 50 0, the line of least resistance is 5m, the millisecond delay time between rows is 25ms, stemming of aperture 140mm is 4.5m, stemming of aperture 90mm is 3m, in the calculation model of the coupling charge, considering the explosive detonation energy spread in the bedrock as seismic waves, so the bottom of model is 1m, in order to reduce the calculation model, and save computing time, even improve the accuracy of the numerical results, the side and bottom of model set as nonreflecting boundary, take 10m as the step gridding, the simulation test point are chosen. The models show in Fig. 1, 2. Fig. 1. Schematic diagram of hole geometry model. Fig. 2. Chart of point selection Numerical simulation analysis In order to simulate the effects of blasting to the bench, the FEM program LS-DYNA is used, the charge parameters and explosive parameters are direct input, through the interaction of hole detonation and explosive detonation, the explosion load is determined. Intersection of hole axis plane and the vertical plane step surface is as a profile, the crossing point is as the starting point, taking 10m as step gridding, the simulation measuring points are

3 870 Zhang Yuanjuan / Procedia Engineering 84 ( 2014 ) choosed, and the three-phase of typical peak vibration velocity is shown in Fig. 3, combined with using the software MATLAB, total energy of the simulation test point and peak particle velocity are shown in Table Vx(m/s) max= Vy(m/s) max= (a) Typical curve of horizontal radial peak velocity (b) Typical curve of vertical peak velocity Vz(m/s) max= (c) Typical curve of horizontal tangential peak velocity Fig. 3. Typical curve of three direction peak velocity. Table 2. Double differential of peak velocity and total energy of blasting. center distance double hole PPVx PPVz The total PPVy(m/s) millisecond (m/s) (m/s) charge blasting (m) E E e e From Table 2, we can see the attenuation law of peak particle vibration velocity and the data of energy blasting vibration obtained with the blast center distance respectively, as shown from Fig. 4 to Fig. 7. From the above figures of the peak vibration velocity attenuation and total energy attenuation law, the peak vibration velocity of blasting vibration and total energy attenuation with the blast center distance is very fast, especially in the area near blasting source, blasting vibration and total energy in the vertical vibration between 14.06m to 34.06m, which the attenuation decay reached nearly 70%, the attenuation of vertical velocity between 34.06m to 44.06m therelatively is more slower; in the same way, in the horizontal radial, the peak vibration velocity

4 Zhang Yuanjuan / Procedia Engineering 84 (2014 ) from 14.06m to 44.06m, almost 80% subsequently decayed rate slowin the horizontal tangential velocity, attenuation from 14.06m to 44.06m reached near 70% subsequently decay rate slow; energy attenuation in the front two measuring points less than 10m attenuation reached 66%, between the 34.06m to 44.06m 10m decayed slowly gradually. The attenuation law of blasting vibration peak velocity is agreement with three-phase attenuation law, the near zone occurs in the blasting vibration, from the numerical results, we can see that between 35m to 45m blast center distance range, the 70% 80% energy of blasting vibration is decayed, it is can be conclused that the attenuation law related to the draw and scholars are also consistent. PPVy (m/s) PPVx m/s blast center distance (m) blast center distancem Fig. 4. Decay curve of vertical vibration velocity with blast center distance. Fig. 5. Decay curve of horizontal radial velocity with blast center distance PPVz (m/s) the total energy blast center distance(m) 0 blast center distancem Fig. 6. Decay curve of horizontal tangential velocity with blasting distance. Fig. 7. Decay curve of the total energy with blasting distance 3. Conclusions In this paper, through peak particle velocity and total energy, the attenuation law of open-pit bench blasting is analysed, it is obtained that the blasting vibration peak velocity and energy attenuation occurred in the area near blasting source, 80% of blasting vibration peak velocity and total energy of the double hole millisecond blasting is decayed in the 35m to 45m from blast center distance, the subsequent slow decay until 0,it provide a theoretical basis for the open-pit slope maintenance and construction of protective structures. Reference [1] DU Hanqing. Experimentally Study on the Attenuation Law ofblasting Vibration[J]. BLASTING(Chinese), chinese,2007,24(3),pp, [2] ZHANG Hua, GAO Fuqiang, YANG Jun, etal. Experimental Studies on Blasting Vibration Velocity Attenuation Law in Deep Open-pitM ining[j]. CTA ARMAMENTARII(Chinese),2010,31(supp1),pp,

5 872 Zhang Yuanjuan / Procedia Engineering 84 ( 2014 ) [3] Livermore Software Technology CorporationLS-DYNA Keyword User's Manual(970v)[M]Livermore, 2003 [4] DING Xi ping, WANG Zhong qian, FENG Shu-yu. Simulation on effect of stemming length to deep hole bench blasting[j]. JOURNAL OF CHINA COAL SOCIETY(Chinese),2001,26(4),pp, [5] ZHANG Yuan juan,huang Jin-xiang,YUAN Hong. STUDY OF SHOCK ABSORPTION EFFECT OF BUFFER BLASTING[J]. Chinese Journal of Rock Mechanics and Engineering(Chinese),2011,30(5),pp, [6] ZHONG Dong wang, LI Shou-gui. An application studyon numerical simulation in presplitting blasting[j]. blasting(chinese), 2001,18(3), pp, [7] ZHANG yuan juan, WANG gong zhong, WANG xing rong, etc. Numerical Simulation Analysis of Blasting Damage Range[J]. Industrial Minerals & Processing, 2013(4),pp: [8] CHEN Xing ming, XIAO Zheng xue, PU Chuan jin. Experimental Study on Influence Blasting EarthquakeStrength to Free Faces[J]. blasting, (Chinese),2009,26(4),pp, [9] ZHEN Yu cai, ZHU Chuan yun. Analysis on InfluentialFactors ofvibration Superposition in Middle and Far Field of Millisecond Blasting, [J]. BLASTING(Chinese), 2005,22(2),pp, [10] JANG Li li, LIN Cong mou, CHEN Ze guan, etc. Wavelet Packet Analysis of Vibration Caused by High Rock Slope Blasting[J]. Nonferrous Metals(Mining Section) (Chinese), 2009, 61(2), pp, [11] Tang C A, Kaiser P K. Numerical simulation cumulative damage and seismicity energy release in unstable failure of brittle rock-partñ. Fundamentals [J] Int J Rock Meeh & Min Sci, 1998, 35 (2),pp,