raili

83,

ina

Available online 2 May 2011

Keywords:

Final pit walls stability

Waveform interference

is

l da

. It

e e

propagation of blasting induced ground vibrations and nd the feasible approaches to reduce the

harmful effects of vibrations induced by blasting on the nal pit walls stability. For this purpose,

a series of eld experiments were conducted in XinQiao Mining Co. Ltd. Sixty-six events and the

pen-pent, thd. Accl incre

as athe

enterverythe

than those of high [5]. Articial neural networks have been used

Contents lists available at ScienceDirect

journal homepage: www.els

Soil Dynamics and Ear

Soil Dynamics and Earthquake Engineering 31 (2011) 11541158sciousness. Early years, the criteria for estimating the damageE-mail address: sxzcsu@163.com (X.Z. Shi).to predict and control ground vibration in mines but its accuracydepends on the number of inputs [57].

Various countries have their own specications set on thebasis of case study of observed damages and their safety con-

0267-7261/$ - see front matter Crown Copyright & 2011 Published by Elsevier Ltd. All rights reserved.

doi:10.1016/j.soildyn.2011.04.004

n Corresponding author at: School of Resources and Safety Engineering, Central South

University, Changsha 410083, China. Tel.: 86 13974801752; fax: 86 73188879612.vibrations induced by blasting on the nal pit walls stabilityin this open-pit mine is a critical problem, which affects the

vibrations induced by blasting and the results illustrated that lowfrequency ground vibrations have more damaging capabilitiesof great height, steep, complexity rock properties and lowstability. Small landslide of the nal pit walls has occurred manytimes in Xinqiao Mining. Vibrations induced by mining blastingare considered to have the most negative effects on the nalpit walls stability. Control and reducing negative effects of the

and accurate indicator of possible damage. PPV is useddamage criterion but it could not explain its effect onfacilities, which may be situated very far away from the cpoint of blasting location and even damaged when PPV islow. So some researchers used spectral analysis to studywhen the open-pit mine will be closed. Pre-splitting blasting hasalmost not been adopted near the nal pit walls during miningin the past, as a result, the slopes surface is not smooth, andthe rock mass of the slope adjacent to surface was deterioratedto some extent. The nal pit walls have the characteristics

and Nordlund [1], Dowing and Gilbert [2], Adiguzel [3] andSiskind et al. [4]. In this investigation, many statutory measureshave been given to prevent the damaging capabilities of blastinginduced vibrations. As we all know, it is well accepted that thePeak Particle Velocity (PPV) is regarded as the most appropriate1. Introduction

Xinqiao Mining Co., Ltd has an oton Pyrites production p.a. At presabout 200 m height have occurreproject, the height of the slope wilblasting parameters of these shots were carefully recorded. During the statistical analysis of the

collected data, the predictor equation proposed by the United States Bureau of Mines (USBM) was used

to establish a relationship between the Peak Particle Velocity (PPV) and the Scaled Distance (SD) factor.

The relationship between PPV and SD was determined and proposed to be used in this open-pit mine.

Control of maximum charge amount per delay and the selection optimum interval time to reduce the

intensity of vibration by waveform interference were applied in practice. Based on the eld

experiments, we can determine the maximum charge amount per delay and 15 ms delay were

proposed to be used in this site, and a decrease in vibration of 24.5% was obtained.

Crown Copyright & 2011 Published by Elsevier Ltd. All rights reserved.

it mine with 4 millione nal pit walls withording to the miningase to 400 m or above

mining safety and the sustainable development of XinqiaoMining Co., Ltd. It is very important to measure and controlthe vibrations induced by blasting with a greater degree ofaccuracy.

There are a number of documents devoted to study theblasting induced vibrations in open-pit mines, such as MalmagrenOpen-pit mine

Blasting induced vibrationsDelay time optimization in blasting opevibration-effects on nal pit walls stab

X.Z. Shi a,b,n, SH.R Chen a

a School of Resources and Safety Engineering, Central South University, Changsha 4100b Postdoctoral Workstation of Daye Nonferrous Metals Company, Huangshi 435005, Ch

a r t i c l e i n f o

Article history:

Received 14 March 2009

Received in revised form

1 April 2011

Accepted 10 April 2011

a b s t r a c t

Blasting induced vibration

vibration can cause critica

the nal pit walls stability

the mitigation of negativtions for mitigating thety

China

one of the fundamental problems in the open-pit mines and intense

mage to structures and plants nearby the open-pit mines, especially to

is very important to study how to control vibration induced by blasting in

ffects of blasting in open-pit mines. This study aims to examine the

evier.com/locate/soildyn

thquake Engineering

xed, and also to give some feasible measures to mitigate the

the surface smooth. Before measuring, use gypsum powder and

software, these data pairs with respect to predictors, weresubjected to regression analysis.

X.Z. Shi, SH.R Chen / Soil Dynamics and Earthquake Engineering 31 (2011) 11541158 1155water to x velocity recording instruments at the monitoringstation points.

3. Procedures of investigations for blast induced vibrations

3.1. Indicators of vibration density

It is well known that indicators of blasting induced vibrationsintensity include particle displacement, particle velocity, particleacceleration and frequency. It is not unication view, whichindicators should be the best way to evaluate the effects ofdamage caused by blasting induced vibrations, and now mostresearchers support the view that PPV is the most appropriateindicator of blasting induced vibrations. Particle velocity,frequency, particle displacement and particle acceleration areconsidered in the criterion of blasting induced vibrations damagelevel in Sweden, but in USA., Germany and Finland, particlevelocity and frequency are both considered [5]. In China, Blastingnegative effects of blasting induced vibrations on the nal pitwalls stability.

2. Geology and monitoring points

The rock type of nal pit walls includes hardness rock andsome soft rock. Hard strata include Troilite, Scapolite, Dolomiteand Quartz. These strata have great solidity. Jointing is welldeveloped. Softy strata include schermakite, Phengite, Zoisiteand these strata are greatly affected by geology structure.

To survey more blasting induced vibrations parameters, mon-itoring points should be placed from shot location center to faraway from blasting center. Selected monitoring station pointsshould be convenient to assemble instruments and the represen-tatives of points are also considered. In this site, 6 monitoringstation points were placed at benches with different elevations.Seismic YBJ-1 type of blasting induced vibrations self-recordinginstrument produced by Yangtze River Scientic Research Insti-tute and CD-1 type of velocity recording instrument supplied byBeijing Instrument Factory were adopted in this study. Thevibrations induced by blasting can be grouped into two typesbased on frequency. High frequency varied between 22 and 80 Hzwhile low frequency ranged from 6 to 12 Hz [8]. The frequencyrange of 5500 Hz measuring system is often selected accordingto the common blasting induced vibration frequency. Monitoringstation points should be located on the bedrock rather thanrecovering soil. At rst, using water to wash bedrock surface,then, using sand, cement and water to ll the surface and makelevels was based on PPV developed by various researchers such asKuzu cengiz and Ergin Hasan, 2005; Khandelwal M. and Singh TN.,2007; Singh TN., 2004 [810]. Both PPV and frequency were usedas the damage criterion in the 1980s and later years. There havebeen various research studied to eliminate or mitigate thenegative effects of blasting induced vibrations. One group triesto mitigate vibration by changing explosive type or amount, blast-hole geometry. Another group aims at decreasing the openingarticial discontinuities such as pre-splitting, barrier holes andtrenches [1113].

The intensity of blasting induced vibration often makes thenal pit wall slide. The purposes of this study are to determine thepropagation characteristics of vibrations induced by blastingbased on eld monitoring in this site after the geometric blastingparameters (sub-grade, depth, burden, spacing and collar) areSafety Regulations supports that PPV and frequency shouldPPV 812:83 SD1:12 R2 0:84 3

where, R2 is coefcient of correlation. The R2 quantity is generallyaccepted as a basic measure of the quality of the t. The highestvalue of R2 is obtained from the prediction equation. So thisprediction empirical equation can be accepted as the attenuationempirical formula of this open-pit mine and can be used in thepreparation of practical blasting charts. In order to increase thecondence of prediction, the obtained prediction model should beupdated by including new shots records in the regression analysisdata. The measuring points and the regression curve can bebe taken account into evaluating blasting induced vibrationsdamage [14]. Dynamic stress ratio was proposed to be taken asindictor to study slope stability in other research projects by ourgroup [15].

Particle vibrations induced by blasting include vertical vibra-tion velocity, radial vibration velocity and tangential velocity.A number of site measuring results showed that the peak verticalparticle vibration velocity is the biggest among the three compo-nents of vibrations induced by blasting. So the peak verticalparticle velocities of the monitoring points have been tested atthe scene.

3.2. Empirical attenuation equation

For PPV predictions, a lot of predictors were proposed inliteratures by different researchers [9]. Empirical Eq. (1) has beenselected to be used in this study [16]:

PPV K RQ

p !a

K SDa 1

where Q is the maximum charge amount per delay in kg, R is thedistance between the monitoring station points and the center ofshot location in meters, SD is scaled distance in m/kg1/2. K and aare site factors that vary with foundation conditions, blastinggeometry and type of explosives, which can be determined byregression analysis.

The vibrations induced by blasting data pairs were trans-formed into loglog space, we can get

lgPPV lgKa lgSD 2

Field tests were located at the south side of the open-pit mine.The elevation of shot location center is 294.00 m. The parametersof charge amount per delay and the distance between the shotlocation center and the station were recorded carefully. Thedistances between shot points and monitor stations were deter-mined by GPS. Sixty-six station points were selected on the spot.The diameter of hole is 250 mm, the burden is 5 m, the borespacing is 6 m, the row spacing is 5 m, the depth of bore is 14 mand ANFO are used at this open-pit mine. Basic parametersrelated to blasting induced vibrations and eld test results aregiven in Table 1.

Sixty-six records of blasting induced vibrations are to beanalyzed. When statistical analysis techniques are applied toanalysis blasting induced vibrations data pairs, peak particlevelocity and scaled distance factor give a site-specic velocityempirical attenuation equation (see formula (3)). By using Mat labshown graphically in Fig. 1.

Control of maximum charge per delay, pre-splitting blasting,adjusting the direction of the burden, decoupling charge struc-ture, etc., measures are commonly used to reduce blastinginduced vibrations intensity. Adjusting the direction of theburden tends to be limited by geology and production scale. Inthis site, in addition to using the pre-splitting blasting method tomaintain the nal pit walls stability, control of maximum charge

X.Z. Shi, SH.R Chen / Soil Dynamics and Earthquake Engineering 31 (2011) 115411581156Table 1Vibration measurements taken in the site.

SD (m/kg1/2) PPV (mm) Frequency

(Hz)

SD (m/kg1/2) PPV (mm) Frequency

(Hz)

6.07 122.8 64.3 6.28 146.7 49.8

12.03 57.0 32.6 12.33 67.1 42.3

30.43 25.5 26.4 21.94 52.1 38.44. Field tests

4.1. Determination of maximum charge amount per delay

In order to suppress the blasting induced vibrations effects andmitigate the possible hazard on nal pit walls stability, the valueof PPV induced by blasting should be controlled within thethreshold damage limits of the Blasting Safety Regulations.

per delay and waveform interference caused by delay blastingwere used to mitigate the possible hazard on nal pit walls.

Empirical attenuation Eq. (3) reects the propagation charac-

33.55 14.5 18.3 39.26 5.6 5.3

39.61 9.0 10.7 67.33 7.1 10.2

9.74 40.2 36.9 74.66 6.2 12.7

8.01 54.0 48.1 78.05 5.8 11.2

10.96 116.3 62.9 87.55 4.9 7.9

20.18 55.8 40.3 103.76 3.9 6.8

23.04 47.7 45.2 5.10 173.1 102.4

35.49 8.8 10.5 9.21 150.2 87.2

41.77 8.1 9.3 16.89 90.6 42.1

4.82 72.1 48.9 29.35 38.6 21.0

3.92 85.9 39.1 32.61 26.3 14.3

5.20 163.6 90.4 35.27 14.7 10.8

9.55 61.4 32.3 38.35 13.2 11.7

10.93 50.5 29.8 45.59 10.6 12.5

11.38 36.0 16.2 51.97 8.9 9.8

13.49 30.1 12.8 23.45 24.0 14.7

16.92 23.5 18.3 26.72 18.1 12.5

19.94 19.7 16.7 18.92 27.9 17.0

4.75 143.0 78.2 33.45 14.9 14.9

8.91 71.6 43.2 43.21 13.2 10.2

13.35 45.9 32.0 24.52 21.0 13.8

25.71 22.3 12.7 56.21 9.4 10.6

46.02 11.7 13.9 31.41 17.0 14.2

34.67 16.0 11.6 42.58 10.4 11.9

13.58 45.0 21.0 5.87 105.0 62.8

26.91 23.2 13.4 7.62 74.8 32.8

34.90 14.9 12.8 13.45 41.6 26.7

45.89 16.8 11.2 24.74 22.8 16.1

57.24 12.2 10.8 25.62 19.2 15.3

6.94 84.2 43.7 28.71 17.3 12.7

0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.40

0.5

1

1.5

2

2.5

LogSD

LogP

PV

lgPPV = - 1.12lgSD + 2.91

Data PointsBest Linear Fit

Fig. 1. LogSDLogPPV graphs for records.teristics of blasting induced vibrations in this open-pit mine andthe formula can be changed to the following formula:

Q PPV R1:12

812:83

1:7864

According to the above formula, as long as determining thethreshold damage limits of the nal pit walls stability is con-cerned, maximum charge amount per delay in this site permittedin order to maintain the nal pit walls stability can be deter-mined by formula (4). The threshold damage limit of PPV can bedetermined by industry norms, and it can also be determinedbased on the conditions of the site including geological structuresdistributions and the nature of the rock. After a series of surveysand studies, PPV values of 180 mm/s was denoted as the criterionto prevent the nal pit walls from damage under the action ofblasting induced vibrations [17]. In practice, we can determinethe maximum charge amount per delay by the empirical Eq. (4).According to the production scale, the total charge amount of ashot can be determined. So we can determine the number ofdelays based on total charge amount of a shot and maximumcharge amount per delay. The most signicant aspect ion mitigat-ing the damage is the increased number of delays, which canminimize the amount of explosive detonated at any instant,reducing negative effects of vibrations induced by blasting,especially in areas of sensitive slope stability.

Chinese Standards of slopes stability permitting peak particlevelocity advised by national safety regulation of blasting is listedin Table 2.

4.2. Practical blasting charts

The frequencies of recorded peak particle velocities are givenin Fig. 2. This graph shows that a major part of the recordedfrequencies varies from 10 to 50 Hz. The ratio of vibrations withfrequencies between 10 and 50 Hz dominates 82% and the ratio ofvibrations with frequencies of higher than 50 Hz is 10%. The ratioof vibrations with frequencies of lower than 10 Hz is 8%. So it canbe said that the open-pit mine can be classied as a lowfrequency site.

Based on the empirical attenuation equation, PPV and max-imum charge amount per delay for this open-pit mine can beestimated by chart given in Figs. 3 and 4.

Peak particle velocity depending on maximum charge amountper delay and the distance from shot location center to

Table 2Blasting induced vibration permitted according to Chinese standard.

Protective structure Permitted PPV /cm/s/

o10 Hz 1050 Hz 50100 Hz

House built of soil 0.51.0 1.11.5 1.11.5

House built of brick 2.02.5 2.32.8 2.73.0

Reinforced concrete structure 3.04.0 3.54.5 4.25.0

Ancient relic 0.10.3 0.20.4 0.30.5

Roadway in mine 1530

X.Z. Shi, SH.R Chen / Soil Dynamics and Earthquake Engineering 31 (2011) 11541158 1157>50Hz 11%

intensity of blasting induced vibrations by waveform interference

blasting induced vibrations, and preservation of inherent rock

Mining Co., Ltd. The authors are grateful to the School ofResources and Safety Engineering of Center South Universityand Xinqiao Mining Co. Ltd for their supports. The authors arealso very grateful to the staff of the open-pit mine of XinqiaoMining Co., Ltd for their hospitality and invaluable support duringthe eld investigation.

References

[1] Malmagren L, Nordlund E. Behavior of shotcrete supported rock wedgessubjected to blast-induced vibrations. International Journal of RockMechanics and Mining Sciences 2006;43:593615.

[2] Dowing CH, Gilbert C. Dynamic stability of rock slopes and high frequency

Table 3Results of vibration reduction experiments.

Delay time (ms) Reduction ratio (%) Success ratio (%)

15 24.5 77.6

25 23.7 49.030 34.3 50.035 12.1 70.5

40 21.4 74.6

X.Z. Shi, SH.R Chen / Soil Dynamics and Earthquake Engineering 31 (2011) 115411581158strength and maximization of nal pit walls stability.

Acknowledgments

This work was supported by the School of Resources andSafety Engineering of Central South University and Xinqiaoin this open-pit mine is effective.

5. Conclusions

After eld measuring the vibrations induced by blasting andcarrying out statistical analysis, the regulation of vibration pro-pagation in this site has been obtained.

According to blasting induced vibrations characteristics, com-bined with the actual situation of the open-pit, comprehensivemeasures are developed to suppress the vibration effects andmitigate the possible hazard on the nal pit walls. Control ofmaximum charge weight per delay and interference method havebeen used in this site to solve the contradiction between the scaleof production and suppress the vibration induced by blasting,control of maximum charge weight per delay and interferencemethod have been used in this site. The formula used todetermine the maximum charge weight per delay is given.15 ms of the appropriate delay time in this open-pit mine isdetermined by eld experiments, and the results illustrated thatthe average decline rate of 24.5% was reached. The ultimate goalsof this research work are optimization of delay time and controlmaximum charge amount per delay, elimination of unacceptabledetonators with 15, 30, 45, 60, 75, 90, 105 and 135 ms delay timeshave been used in this open-pit mine. The intensity of vibrationsinduced by blasting was reduced by 24.5% on the new intervalring. The blasting induced vibrations have been measured in thissite for a long period, and the results illustrate that mitigating the[3] Adiguzel D. The investigation of ground vibrations induced by bench blastingat Akyol quarry at Catalca region in Turkey. MSc Thesis in Turkish, IstanbulUniversity, Istanbul; 2006, p. 28.

[4] Siskind DE, Stagg MS, Kopp JW, et al. Structure response and damageproduced by ground vibration from surface mine blasting. USBM RI 8507;1980, p. 74.

[5] Singh TN, Singh Virendra. An intelligent approach to prediction and controlground vibration in mines. Geotechnical and Geological Engineering2005;223:24962.

[6] Shimshoni Y. Classication of Seismic signals by integration ensembles ofneural network. IEEE Transactions on Signal Processing 1998;46(5):1094101.

[7] Wei Shen, Quan jun XU, Mao rong JI. Using BP articial neural network topredict bench blast vibration parameters. Explosion and Shock Waves2002;24(2):3537. (in Chinese).

[8] kuzu Cengiz, Ergin Hasan. An assessment of environmental impacts ofquarry-blasting operation. A case study in Istanbul, Turkey. EnvironmentalGeology 2005;48(5):2117.

[9] Khandelwal M, Singh TN. Evaluation of blast induced ground vibrationpredictors. Soil Dynamics and Earthquake Engineering 2007;27(2):11625.

[10] Singh TN. Articial neural network approach for prediction and control ofground vibrations in mines. Mining Technology (Transactions of the Institu-tion of Mining and Metallurgy Section A) 2004;113:2517.

[11] Yang YB, Huang HH. A parametric study of wave barriers for reduction oftrain-induced vibrations. International Journal for Numerical Methods inEngineering 1997;40(20):372947.

[12] Dowing CH, Gilbert C. Dynamic stability of rock slopes and high frequencytraveling waves. Journal of Geotechnical Engineering. 1988;114(10):106988.

[13] Dowing CH. Monitoring and control of blasting effects. In: Mining engineer-ing handbook. Prentice Hall; 1985, p. 6689.

[14] Zhixing YAN, Delun WU, Yi WANG. The study of blast vibration effect andsafety. Rock and Soil Mechanics 2002;23(2):2013. in Chinese.

[15] Guangming SONG, Xiuzhi SHI, Shouru CHEN. New method for determiningblasting vibration damage criterion on open-pit slope and its application.Journal of Central South University of Technology (Natural Science)2006;36(6):4858. (in Chinese).

[16] Zhen-zhi WU, Guo-xiang HU, Zong-wei DENG. Discussion on the safetycriteria for blasting vibration. Safety and Environmental Engineering 2003;10(4):646. (in Chinese).

[17] Zhi yuan MAO, Quanjun XU. An engineering practice on safety criterion ofblasting vibration considering the effect of frequency. Engineering Blasting2001;7(3):1922. (in Chinese).

[18] Shouru CHEN, Yanling LI, Shengquan XIE. Experimental study of blastingvibration reduction by waveform interference in an open slope. Journal ofHunan University of Science and Technology (Natural Science Edition)2004;19(2):103. (in Chinese).vibrations of different intervals are magnied. In practice, delay traveling waves. Journal of Geotechnical Engineering 1998;114(10):106988.be seen from the test results that, when delay time is 15 ms, thesuccess ratio of vibrations reduce and the decrease degree ofvibrations are high, but when delay time is 25 or 30 ms, the

Delay time optimization in blasting operations for mitigating the vibration-effects on final pit walls' stabilityIntroductionGeology and monitoring pointsProcedures of investigations for blast induced vibrationsIndicators of vibration densityEmpirical attenuation equation

Field testsDetermination of maximum charge amount per delayPractical blasting chartsWaveform interference

ConclusionsAcknowledgmentsReferences