A Certain Open Pit Slope Blasting Vibration Law Research

Transcription

1 nd International Conference on Architectural Engineering and New Materials (ICAENM 2017) ISBN: A Certain Open Pit Slope Blasting Vibration Law Research Lihua He ABSTRACT In order to study the open-pit mine stope of high bench blasting vibration on slope stability, the influence of the blasting vibration signal test system of a certain open-pit mine stope surrounding high slope blasting vibration monitoring, obtain vibration data, according to Steve Sadove, experience formula and Hilbert Huang transform (HHT) blasting vibration signal analysis method, the attenuation law of blasting vibration on slope, slope was the main vibration frequency of vibration. According to Sadov s formula, experience formula and Hilbert Huang transform (HHT) analysis results, and on the basis of the blasting safety regulations (GB ) for minimum safety distance is 86 m, slope for mining in the aspect of reducing the influence of blasting vibration on slope take corresponding measures to provide a reference basis. 1 INTRODUCTION With the exploitation of mine brings negative effects, such as blasting vibration and flying rock, and the stability of the high and steep slope in open-pit mine is affected and other issues have been brought to the attention of the people more and more high[1-2]. Blasting operation adds momentum to the slope sliding, destroyed the slope rock mass, reduces the strength of the rock mass at the same time, the lower the slope stability. Blasting vibration on high and steep open ore-bearing rock mass slope stability influence is bigger, its directly endanger the mine's normal production and the life property safety of the workers. Therefore, research on blasting vibration monitoring, explore the propagation rules of blasting vibration, 1 Lihua He, Institute of Mining, Kunming Metallurgy College, Kunming, China,

2 can judge the stability of the slope, and timely make reasonable design scheme, ensure the safety of the construction in the process of production. PROJECT SUMMARY One with the increase of mining depth and time, in open stope mining slope around heightening, has now formed a slope of about 400 m high, the slope Angle of high slope. Need because of the open pit mining in frequent blasting construction, and the frequent blasting activities will produce larger blasting vibration, blasting vibration effect to mining area side effects and a series of states to cause major damage, makes the slope constant disturbance, thus there is the possibility of a serious instability, seriously affect the mine safety production. BLASTING VIBRATION TESTING In the actual blasting vibration monitoring of blasting vibration peak velocity and peak acceleration of monitoring is the most widespread. According to the Safety regulations for blasting (GB )[3], mainly for blasting vibration velocity and vibration frequency of the corresponding measure on the strength of the standard to judge whether the blasting vibration damage to protect object. Rock slope blasting vibration in the vibration velocity of particles into radial, tangential and vertical three directions. And in the vibration velocity of blasting vibration three directions, vertical vibration will have bigger influence on the slope rock mass. In monitoring the blasting vibration velocity, therefore, in this paper, based on the vertical direction vibration velocity and vibration wave and at the same frequency as the research object. Monitoring Instruments and Methods The blasting vibration testing instruments used in Chengdu zhongke measurement and control co., LTD. Production of TC-4850 blasting vibration and speed sensor. The blasting vibration test system is made up of speed sensor, the blasting vibration meter, computer, printer etc together. As is shown in figure 1. Arrangement of Measuring Points In the blasting vibration monitoring, measuring point position is particularly important for the layout of its great influence the reliability and accuracy of monitoring data. In the study of blasting vibration wave attenuation rule in the medium and determining the safe distance, the general adopt the method of multiple point a measuring line layout. 458

3 Through the communication with the mine, the blasting area set up four side slope blasting vibration test lines, each line layout of 5 points, arrangement of measuring points in each one instrument, instrument layout directly on the surface of the rock. Critical area and the arrangement of measuring points is shown in figure 2. Figure 1. Blasting vibration test system schematic diagram. Figure 2. Critical area and the arrangement of measuring points. 459

4 MONITORING DATA PROCESSING AND ANALYSIS Monitoring Results After completion of measuring-point arrangement, after many tests, get different results under the charge of blasting vibration velocity and vibration frequency, as shown in table 1: P: the arrangement of measuring points, A: altitude, N: Instrument serial number, G: maximum tolerant explosive quantity of single shot, L: distance from the explosion center, V: Peak vibration velocity, f: Peak vibration velocity. 460

5 Regression Analysis of Blasting Vibration Signals Based on Sadov Formula In engineering applications, the empirical formula of Sadov is used to analyze the propagation and attenuation of blasting vibration[4-5]. It expresses the relation between the particle vibration velocity and the charge quantity and the distance of the core: 1/3 V = K ( Q / R) α (1) Where: V is the maximum speed of particle vibration (cm/s); Q is the amount of explosives (kg); R is the burst distance (m); K and α are the coefficient and attenuation index related to topography and geological conditions between the blasting point and the measuring point. According to the blasting vibration test results, respectively, selected 1, 2, 3, 4 vibration measurement points on the measured vibration data on the line (Table 1), The regression formula of Sadov is given by Matlab software, to arrive at four vibration measurement line K, α value, the regression results shown in Table 2 and Figure 3. TABLE II. B LASTING VIBRATION PROPAGATION LAW STATISTICS REGRESSION RESULTS. Line K α Fitting vibration formula R-Square number No Q v = R Root mean square error No No No Q v = R 3 Q v = R 3 Q v = R

6 No. 1 line No. 2 line No. 3 line No. 4 line Figure 3. Steve Sadove each line, the formula of linear regression. Analysis of Blasting Vibration Propagation Based on HHT Method In order to adequately analyze the measured vibration wave signal, this time selected Hilbert Huang (HHT) algorithm for waveform time-frequency analysis[6-11]. HHT method is one of the methods of time-frequency localization analysis which is widely recognized at home and abroad. The program consists of two parts, EMD method and Hilbert transform. EMD method is the key to HHT method, which can remove the interference wave and make the waveform more symmetrical. The Hilbert spectrum can be obtained by combining the instantaneous spectrum with the Hilbert transform of the IMF signal combination obtained by EMD method. Hilbert transform mainly reflects the localized characteristics of the signal. The instantaneous spectrum mainly measures the distribution of energy in frequency. HHT method is more suitable for dealing with time-frequency localized analysis of non-stationary signals. It can distinguish singular signals from low-frequency 462

7 signals, which can represent the main characteristics of signal changes. It is suitable for analyzing the blasting vibration signals with rapid mutation and decay. Figure 4. The original waveform figure. Figure 5. Marginal spectrum. Figure 6. The energy distribution. Figure 7. The instantaneous energy spectrum. Figure 8. The three dimensional spectrum. At the same time, due to the limitation of space, this paper only selects a set of blasting vibration signals measured on the slope of mine, and uses HHT method to 463

8 analyze the time-frequency characteristics. Analysis results are shown in Figure 4 to figure 8: Figure 4 is the original waveform. Figure 5 is the marginal spectrum of blasting vibration signals. It expresses the magnitude of each frequency at the global scale, representing the full cumulative amplitude in the statistical sense. Figure 6 shows the energy distribution, which mainly expresses the energy accumulated by each frequency in the whole time. It can be seen from Figure 6 that the signal frequency of the vibration signal is quite full, and the dominant frequency distribution is mainly about 10Hz. Figure 7 shows the instantaneous energy spectrum, and the signal is the result of multiple detonators, which is caused by the superposition of the adjacent blasting holes in the process of hole blasting. As can be seen from the diagram, the instantaneous energy spectrum of the vibration wave collected in the range of 0~0.6s is relatively concentrated. Figure 8 is the three dimensional spectrum of blasting vibration signal. The color map said energy, colour more bright color, on behalf of the higher the energy, on the other hand, the lower energy. As the result of the blasting vibration signal analysis of HHT can be found after the blasting vibration wave from the explosion area spread to the slope of high frequency gradually decay, mainly in the low frequency signal frequency, mainly distributed in the range of 0 ~ 50Hz, and the dominant frequency band energy is mainly concentrated in the range of 0 ~ 10Hz, which indicates that the blasting vibration wave on the slope the main influence for low frequency wave, so the study of blasting vibration on the slope stability of low frequency waves to be considered 0~10Hz. Slope Safety Distance The length of blasting area directly affects the stability of blasting vibration. With the exploitation of the stope slope near the slope more when the particle vibration velocity increases, when the particle vibration velocity can lead to slope instability began, and the blasting area to the side slope distance called slope safety distance. According to the standard of blasting vibration safety in Safety regulations for blasting (GB ), it can be seen that when the vibration frequency is in the range of 10Hz, the safety vibration velocity of the particle should be 5~9cm/s. Because the mine slope is mainly in the range of 0-10Hz low frequency vibration wave effect, in order to ensure the slope safety and stability, can select the maximum mine slope safety allows the particle vibration velocity is 5cm/s, according to the Sadov s formula design of blasting parameters of single hole charge and each measured line of slope to obtain the minimum safety distance. As follows: The minimum safety distance of the slope of No.1 survey line is 81m. The minimum safety distance of the slope of No.2 survey line is 86m. The minimum safety distance of the slope of No.3 survey line is 73m. The minimum safety distance of the slope of No.4 survey line is 63m. 464

9 Based on the comparative analysis of the minimum safety distance of four slope, it can be seen that the minimum safety distance between the mining area and the boundary slope is 86m. When the distance between the blasting area and the final slope is less than the minimum safe distance, the stability of the slope will be hidden. CONCLUSION (1) According to the blasting vibration data, the use of Sadov s formula of the fitting coefficients for K topographic and geological conditions of 4 lines and the attenuation index values and the corresponding propagation of blasting vibration formula. (2) A set of measured blasting vibration data is selected, and the HHT analysis is carried out. The slope is mainly affected by the low frequency wave, and the frequency of the vibration wave is about 0~10Hz. (3) Through the analysis of the slope vibration signal, on the basis of Safety regulations for blasting (GB ) in the blasting vibration safety standard, select the maximum allowable safety vibration velocity of slope 5cm/s, and according to the Sadov s formula, the blasting parameters and the single hole charge line to obtain the slope minimum safety distance of 86m, to provide reference basis for the mine to take corresponding measures to reduce the influence of blasting vibration on the slope. REFERENCES 1. Laishan Chang, Yujiang Yang. Stability analysis and control of open-pit slope[m]. Beijing: Metallurgical industry press, Zhixin Yan, Yonghe Wang, Ping Jiang, et al. Study on measurement of blast-induced seism and building safety criteria[j]. Chinese Journal of Rock Mechanics and Engineering, 2003, 22(11): Standards of the people's Republic of China. GB Safety regulations for blasting[s]. Beijing: China Standard Press, Chengyu Xie, Zhouquan Luo, Nan Jia, et al. Dynamic effects of open blasting vibration on adjacent buildings and measures for vibration reduction [J]. Journal of Vibration and Shock, 2013, 32(13): Zhiyi Zhang, Nianhua Yang, Wenbo Lu, et al. Progress of Blasting Vibration Control Technology in China[J]. Blasting, 2013, 30(2): Derong Bao, Yongtao Gao, Shu Xiao, et al. Monitoring of Blasting Vibration and Numerical Simulation of a Foreign Open-pit Mine Slope[J].Modern mining, 2015(12): Xinpu Zhao. Research of attenuation law of blasting vibration and effects caused by accumulated damage[d]. Liaoning: Liaoning Technical University, Wenbo Lu, W. Hustrulid. An improvement to the equation for the attenuation of the peak particle velocity[j]. Engineering Blasting, 2002, 8(3): Xibing Li, Yiping Zhang, Zhixiang Liu, et al. Wavelet analysis and Hilbert-Huang transform of blasting vibration signal[j].explosion and Shock Waves, 2005, 25(6):

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