blast-induced air and ground vibration prediction: a particle swarm optimization-based artificial...

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ORIGINAL ARTICLE Blast-induced air and ground vibration prediction: a particle swarm optimization-based artificial neural network approach Mohsen Hajihassani 1 Danial Jahed Armaghani 2 Masoud Monjezi 3 Edy Tonnizam Mohamad 2 Aminaton Marto 2 Received: 28 January 2014 / Accepted: 1 March 2015 Ó Springer-Verlag Berlin Heidelberg 2015 Abstract Mines, quarries, and construction sites face environmental damages due to blasting environmental impacts such as ground vibration and air overpressure. These phenomena may cause damage to structures, groundwater, and ecology of the nearby area. Several empirical predictors have been proposed by various scholars to estimate ground vibration and air overpressure, but these methods are inapplicable in many conditions. However, prediction of ground vibration and air over- pressure is complicated as a consequence of the fact that a large number of influential parameters are involved. In this study, a hybrid model of an artificial neural network and a particle swarm optimization algorithm was implemented to predict ground vibration and air overpressure induced by blasting. To develop this model, 88 datasets including the parameters with the greatest influence on ground vibration and air overpressure were collected from a granite quarry site in Malaysia. The results obtained by the proposed model were compared with the measured values as well as with the results of empirical predictors. The results indicate that the proposed model is an applicable and accurate tool to predict ground vibration and air overpressure induced by blasting. Keywords Vibration blasting impacts Ground vibration Air overpressure Artificial neural network Particle swarm optimization Introduction In rock quarry blasting, only 20–30 % of the energy pro- duced by explosives is utilized to fragment and displace the rock mass. The rest of the energy is wasted and produces undesirable environmental impacts such as ground vibra- tion, air overpressure (AOp), flyrock, and back-break (Se- garra et al. 2010; Monjezi et al. 2012; Raina et al. 2014; Jahed Armaghani et al. 2014; Marto et al. 2014; Ebrahimi et al. 2015). Various empirical predictors have been established to predict ground vibration and AOp induced by blasting. However, such approaches only consider limited numbers of parameters influencing ground vibra- tion and AOp, although these phenomena are also affected by other controllable or uncontrollable parameters such as blast geometry and geological conditions (Douglas 1989; Singh and Singh 2005). As a result, in many cases, em- pirical methods are not accurate enough, while prediction of the ground vibration and AOp with a high degree of accuracy is important to estimate the blasting safety area. In addition to the empirical equations, the use of sta- tistical methods such as simple and multiple regression & Masoud Monjezi [email protected] Mohsen Hajihassani [email protected] Danial Jahed Armaghani [email protected] Edy Tonnizam Mohamad [email protected] Aminaton Marto [email protected] 1 Construction Research Alliance, Universiti Teknologi Malaysia, UTM Skudai, 81310 Johor, Malaysia 2 Department of Geotechnics and Transportation, Faculty of Civil Engineering, Universiti Teknologi Malaysia, UTM Skudai, 81310 Johor, Malaysia 3 Department of Mining, Tarbiat Modares University, 14115-143 Tehran, Iran 123 Environ Earth Sci DOI 10.1007/s12665-015-4274-1

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ORIGINAL ARTICLE

Blast-induced air and ground vibration prediction: a particleswarm optimization-based artificial neural network approach

Mohsen Hajihassani1 • Danial Jahed Armaghani2 • Masoud Monjezi3 •

Edy Tonnizam Mohamad2• Aminaton Marto2

Received: 28 January 2014 / Accepted: 1 March 2015

� Springer-Verlag Berlin Heidelberg 2015

Abstract Mines, quarries, and construction sites face

environmental damages due to blasting environmental

impacts such as ground vibration and air overpressure.

These phenomena may cause damage to structures,

groundwater, and ecology of the nearby area. Several

empirical predictors have been proposed by various

scholars to estimate ground vibration and air overpressure,

but these methods are inapplicable in many conditions.

However, prediction of ground vibration and air over-

pressure is complicated as a consequence of the fact that a

large number of influential parameters are involved. In this

study, a hybrid model of an artificial neural network and a

particle swarm optimization algorithm was implemented to

predict ground vibration and air overpressure induced by

blasting. To develop this model, 88 datasets including the

parameters with the greatest influence on ground vibration

and air overpressure were collected from a granite quarry

site in Malaysia. The results obtained by the proposed

model were compared with the measured values as well as

with the results of empirical predictors. The results indicate

that the proposed model is an applicable and accurate tool

to predict ground vibration and air overpressure induced by

blasting.

Keywords Vibration blasting impacts � Ground

vibration � Air overpressure � Artificial neural network �Particle swarm optimization

Introduction

In rock quarry blasting, only 20–30 % of the energy pro-

duced by explosives is utilized to fragment and displace the

rock mass. The rest of the energy is wasted and produces

undesirable environmental impacts such as ground vibra-

tion, air overpressure (AOp), flyrock, and back-break (Se-

garra et al. 2010; Monjezi et al. 2012; Raina et al. 2014;

Jahed Armaghani et al. 2014; Marto et al. 2014; Ebrahimi

et al. 2015). Various empirical predictors have been

established to predict ground vibration and AOp induced

by blasting. However, such approaches only consider

limited numbers of parameters influencing ground vibra-

tion and AOp, although these phenomena are also affected

by other controllable or uncontrollable parameters such as

blast geometry and geological conditions (Douglas 1989;

Singh and Singh 2005). As a result, in many cases, em-

pirical methods are not accurate enough, while prediction

of the ground vibration and AOp with a high degree of

accuracy is important to estimate the blasting safety area.

In addition to the empirical equations, the use of sta-

tistical methods such as simple and multiple regression

& Masoud Monjezi

[email protected]

Mohsen Hajihassani

[email protected]

Danial Jahed Armaghani

[email protected]

Edy Tonnizam Mohamad

[email protected]

Aminaton Marto

[email protected]

1 Construction Research Alliance, Universiti Teknologi

Malaysia, UTM Skudai, 81310 Johor, Malaysia

2 Department of Geotechnics and Transportation, Faculty of

Civil Engineering, Universiti Teknologi Malaysia, UTM

Skudai, 81310 Johor, Malaysia

3 Department of Mining, Tarbiat Modares University,

14115-143 Tehran, Iran

123

Environ Earth Sci

DOI 10.1007/s12665-015-4274-1

techniques for ground vibration and AOp prediction has

received attention mainly due to their ease of use (Hu-

daverdi 2012). Apart from the statistical methods, the use

of soft computing techniques for prediction of ground vi-

bration and AOp recently has been highlighted in the lit-

erature (Khandelwal and Singh 2006; Monjezi et al. 2010,

2011; Mohamed 2011).

Artificial neural networks (ANNs), known as flexible

nonlinear function approximations, have been widely used

to analyze engineering problems. Although ANNs are able

to directly map input to output patterns and utilize all in-

fluential parameters in the prediction of ground vibration

and AOp, there are still some limitations: the slow rate of

learning and the possibility of becoming trapped in local

minima (Eberhart and Shi 1998; Eberhart et al. 1996; Tsou

and MacNish 2003; Hajihassani et al. 2014). To address

these limitations, the use of powerful optimization algo-

rithms such as particle swarm optimization (PSO) is ad-

vantageous for improving ANN performance (Kennedy

and Eberhart 1995; Adhikari and Agrawal 2011; Jahed

Armaghani et al. 2014; Momeni et al. 2015). This study

presents a novel approach founded on a hybrid PSO-based

ANN model to predict ground vibration and AOp induced

by blasting.

Blast vibrations

Blasting operations may cause excessive environmental

impacts such as ground vibration, AOp, dust, and flyrock

(Bhandari 1997). High blast vibrations can cause damage

to structures and nearby residential areas (Konya and

Walter 1990; Singh and Singh 2005). In the following

parts, effective parameters and relevant previous investi-

gations of these vibrations are discussed comprehensively.

Ground vibration

Ground vibration is a wave motion which travels away

from the blast to nearby areas (Khandelwal and Singh

2009). A considerable amount of energy is applied in every

ground vibration in which this energy is supposed to be

applied to rock fracturing. The problems caused by ground

vibration include large impacts on the structures, ground-

water, and ecology of the nearby area (Khandelwal and

Singh 2009; Duvall et al. 1963; Ghasemi et al. 2013).

When an explosive is detonated in a blasthole, the

chemical reaction of the explosives produces a high-pres-

sure and high-temperature gas. This gas pressure crushes

the rock adjacent to the blasthole. The detonation pressure

decays or dissipates quickly. A wave motion is created in

the ground by the strain waves conveyed to the surrounding

rocks (Duvall and Petkof 1959). Due to various breakage

mechanisms like radial cracking, crushing, and reflection

breakage in the free face, the strain energy carried by these

strain waves fragments the rock mass. During and after the

stress wave propagation, high-pressure high-temperature

gases extend radial cracks and any discontinuity, fracture,

or joint (Dowding 1985). The strain waves propagate as

elastic waves when the stress wave intensity diminishes to

the level where no permanent deformation occurs in the

rock mass (see Fig. 1). These waves are identified as

ground vibration. The ground vibration spreads from the

blasthole in all directions (Dowding 1985) and can cause

damage to buildings and other structures (Siskind et al.

1980).

Many parameters are involved in ground vibration such

as the blasting design, the distance between the free face

and the monitoring point, and geological conditions (Wiss

and Linehan 1978; Khandelwal and Singh 2006; Ghoraba

et al. 2015). It is essential to optimize the blasting design

parameters to decrease ground vibration based on the

properties of the rock mass, which include rock strength,

density, wave velocity, and discontinuity conditions (Singh

and Sastry 1986). The ground vibration can be measured in

terms of the peak particle velocity (PPV) and frequency. In

the Indian Standard Institute (Bureau of Indian Standard

1973) and German DIN Standard 4150 (New 1986), the

PPV is considered as a vibration index, which is a sig-

nificant indicator for controlling structural damage. PPV

due to ground vibration in surface blasting is a significant

parameter for the prediction of ground vibration. PPV

principally depends on two parameters: the maximum

charge used per delay and the distance from the free face

(Ozer et al. 2011; Basu and Sen 2005).

Soft computing techniques have been widely used by

several researchers to predict PPV. Singh and Singh (2005)

employed ANN and regression analysis to predict PPV. In

their study, the hole diameter, number of holes, hole depth,

burden, spacing, and the distances from the free face were

considered as input parameters. They demonstrated that

Fig. 1 Ground vibration due to blasting (Bhandari 1997)

Environ Earth Sci

123

ANN is a more accurate approach compared to regression

analysis for predicting ground vibration. Khandelwal and

Singh (2006) investigated four widely used empirical pre-

dictors to estimate the PPV for 150 blast datasets and

compared the computed results with actual field data.

Subsequently, they developed an ANN with two inputs

(maximum charge per delay and distance from free face)

and one output (PPV). They found that ANN results are

more accurate compared to empirical predictors. Iphar

et al. (2008) utilized two different methods including

simple regression and the adaptive neuro-fuzzy inference

system (ANFIS) to predict PPV induced by blasting. They

used 44 PPV values obtained from blasting operations in

Turkey. Their results showed that the ANFIS model

yielded better results in comparison to regression analysis.

Khandelwal and Singh (2009) used ANN and multivariate

regression analysis (MVRA) techniques to predict PPV and

frequency by incorporating rock properties, blast design,

and explosive parameters. A total of 174 vibration records

were used to predict PPV and frequency with ten input

parameters. The ANN results indicated closer agreement

with the field datasets as compared to MVRA prediction.

An ANN model with four input parameters—maximum

charge per delay, distance from the free face to the

monitoring point, stemming length, and hole depth—was

developed by Monjezi et al. (2011) to predict PPV. A

database consisting of 182 datasets was collected at dif-

ferent strategic and vulnerable locations around the Kan-

dovan tunnel in Iran. They demonstrated that ANNs are

applicable tools to predict blast-induced ground vibration.

In addition, from the sensitivity analysis they found that the

distance from the free face has the most influence on PPV,

while stemming has the least. Fisne et al. (2011) utilized a

fuzzy logic approach and classical regression analysis to

predict PPV using 33 datasets obtained from the Akdaglar

quarry in Turkey. In their research, the charge weight and

distance from the free face were considered as input pa-

rameters to predict PPV. They concluded that the predicted

PPVs obtained from the fuzzy model were much closer to

the measured values in comparison to those predicted by

the statistical model. Monjezi et al. (2013) predicted PPV

using different empirical equations and the ANN tech-

nique. They compared the computed results with the actual

field data obtained from Shur River Dam in Iran. Total

charge, maximum charge per delay, and distance between

the shot point and the monitoring station were considered

as input parameters for the prediction of PPV. They found

that the ANN model was more accurate in comparison to

the empirical equations. In another study on PPV predic-

tion, Hajihassani et al. (2014) used a combination of an

imperialism competitive algorithm (ICA)-ANN to predict

PPV values obtained from Harapan Ramai granite quarry.

In their study, the burden-to-spacing ratio, stemming

length, maximum charge per delay, Young’s modulus,

p-wave velocity, and distance from the free face were

utilized as model inputs. They concluded that the ICA-

ANN approach can predict PPV with higher accuracy

compared to empirical equations.

Air overpressure

The explosion (blast) is produced by the shock wave of a

chemical reaction where the pressure of reactive gases

reaches sonic velocity (Baker et al. 1983). The gas pressure

velocity increases rapidly in the blasthole. Consequently,

the pressure in the blasthole suddenly loads the surrounding

rocks, which move away from the borehole. The pressure

in terms of blasting is mainly considered using shock and

gas mechanisms (Roy 2005).

AOp is created by a large wave from the explosion point

to the free surface. Hence, the AOp is a wave which is

refracted horizontally by density variations in the atmo-

sphere. AOp atmospheric pressure waves comprise an

audible high-frequency and a sub-audible low-frequency

sound. Generally, four important sources can cause AOp

waves in blasting operations: the air pressure pulse, which

results from displacement of the rock at the bench face as

the blast progresses; the rock pressure pulse, which is in-

duced by ground vibration; the gas release pulse, which

results from the escape of gases through rock fractures; and

the stemming release pulse, which results from the escape

of gases from the blasthole when the stemming is ejected

(Siskind et al. 1980; Wiss and Linehan 1978; Morhard

1987).

According to Kuzu et al. (2009), AOp is identified in

terms of sound and measured in decibels (dB) or pascals

(Pa), where 20 Hz is the lowest sound detectable by the

human ear. Hence, it is undeniable that there is a possibility

of concussion in the human ear with sound at more than

20 Hz. In addition, structural damage may occur at an AOp

level of 180 dB, general window breakage occurs at

171 dB, and occasional window breakage occurs at

151 dB (Kuzu et al. 2009). According to Siskind et al.

(1980), as reported by the United States Bureau of Mines

(USBM), a value of 134 dB is recommended for AOp

limitation. Therefore, many attempts have been made to

control AOp values (Kuzu et al. 2009; Rodriguez et al.

2010).

Several parameters affect AOp in blasting operations.

According to Khandelwal and Kankar (2011), blast ge-

ometry, explosive charge weight per delay, distance be-

tween the free face and the monitoring point, geological

discontinuities, blasting direction, surface topography, and

vegetation are the foremost parameters influencing AOp.

Konya and Walter (1990) found that AOp can be controlled

by the type and length of stemming materials. Their

Environ Earth Sci

123

findings reveal that a stemming particle size of about 0.05

times the blasthole diameter provides the best confinement

and the materials have to be angular to function properly.

Moreover, other parameters affect AOp, such as over-

charging, weak strata, atmospheric conditions, and sec-

ondary blasting (Siskind et al. 1980; Griffiths et al. 1978;

Dowding 2000). However, AOp induced by blasting is not

easy to predict as the same blast design can produce dif-

ferent results in different cases.

Based on the parameters that influence AOp, many at-

tempts have been made to establish correlations for the

prediction of AOp induced by blasting. Rodrıguez et al.

(2007) developed a semi-empirical model for the predic-

tion of the air wave pressure outside a tunnel due to

blasting. This method was tested in several cases and it was

proven that it can be used under different conditions. Kuzu

et al. (2009) established a new empirical relationship be-

tween AOp and two other parameters (distance between

free face and monitoring point and maximum charge per

delay), which are the most important variables for AOp.

They used 98 AOp records from quarry blasting operations

under different conditions and demonstrated that the pro-

posed equation predicted AOp with reasonable accuracy.

Segarra et al. (2010) provided a new AOp prediction

equation based on monitoring data obtained from two

quarries. Blasting data and AOp measurements were ob-

tained from 122 records of 40 blasting operations in rocks

with low to very low strength. They concluded that the

accuracy of AOp prediction was 32 %. In addition, the

proposed model was validated using five new blasting data

with 22.6 % accuracy.

Apart from empirical equations, some soft computing

methods have been developed to predict AOp. Khandelwal

and Singh (2005) presented an ANN model to predict AOp

from two variables including distance (between free face

and monitoring point) and sound pressure level. They

compared the ANN results with the USBM predictor and

multivariate regression analysis (MVRA) results. The

comparison showed that ANN yielded better estimates

compared to USBM and MVRA predictors. Mohamed

(2011) predicted the AOp using a fuzzy inference system

and ANN using two parameters: maximum charge per

delay and distance from the free face to the monitoring

point. He compared the results with the values obtained by

regression analysis and observed field data, and concluded

that the ANN and fuzzy models gave more accurate pre-

diction compared to regression analysis. Khandelwal and

Kankar (2011) predicted AOp due to blasting using 75

datasets obtained from three mines by the support vector

machine (SVM) method. They compared the AOp values

predicted by SVM with the results of a generalized pre-

dictor equation. Using the maximum charge per delay and

distance from the free face to the monitoring station as

input parameters, they showed that the values of AOp

predicted by SVM were much closer to the actual values as

compared to the values predicted by the generalized pre-

dictor equation. Tonnizam Mohamad et al. (2012) used

ANN to predict AOp using 38 datasets obtained from

blasting operations. In their study, the hole diameter, hole

depth, spacing, burden, stemming, powder factor, and

number of rows were used as input parameters. Their re-

sults show the applicability of the proposed model to the

prediction of AOp.

PPV and AOp prediction methods

Estimating a safe zone for blasting operations is an im-

portant subject in the field of geotechnical engineering, and

prediction of blasting environmental impacts such as PPV

and AOp before blasting operations is always necessary.

Many attempts have been made to predict PPV and AOp

using empirical methods. In the following sections, a brief

review of these empirical methods is presented.

PPV prediction methods

Many researchers established empirical vibration equations

to predict PPV (Duvall and Petkof 1959; Bureau of Indian

Standard 1973; Langefors and Kihlstrom 1963; Davies

et al. 1964; Ghosh and Daemen 1983; Roy 1993). In most

of these equations, the maximum charge per delay and

distance from the free face are considered as the main in-

fluential parameters for PPV prediction. It is well known

that PPV is influenced by other factors such as blast ge-

ometry, rock strength, and discontinuity conditions which

have not been incorporated explicitly in any of the em-

pirical equations. So, different equations give different

PPV values for the same blasting operation and there is no

uniformity among the results predicted by different equa-

tions. Table 1 illustrates the PPV equations proposed by

different researchers.

AOp prediction methods

Some empirical equations have been suggested to predict

AOp. According to the National Association of Australian

State Road Authorities 1983, AOp from confined blasthole

charges can be estimated from the following empirical

formula:

P ¼140

ffiffiffiffiffiffi

E200

3

q

d; ð1Þ

where P is the AOp (kPa), E the mass of charge per delay

(kg), and d the distance from the free face (m). McKenzine

Environ Earth Sci

123

(1990) recommended an equation to describe the decay of

AOp as follows:

dB ¼ 165� 24logðD=W1=3Þ; ð2Þ

where dB is the decibel reading with a linear of flat

weighting, D the distance between the free face and the

monitoring point (m), and W the explosive charge weight

per delay (kg).

Applying the cube root scaled distance factor (SD), in

the absence of monitoring equipment, is another method of

estimating the blast-induced AOp. The correlation between

explosive charge weight per delay, distance, and SD is

given as follows:

SD ¼ DW�0:33; ð3Þ

where D denotes the distance (m or ft), W the explosive

charge weight (kg or lb), and SD the scaled distance

(m kg-0.33 or ft lb-0.33).

Through the availability of sufficient data, establishment

of the relationship between the values of SD and AOp is

possible. A site-specific AOp attenuation formula can be

developed when statistical analysis techniques can practi-

cally represent AOp data (White and Farnfield 1993;

Rosenthal and Morlock 1987; Cengiz 2008). The predic-

tion equation is shown as follows:

AOp ¼ HðSDÞ�b; ð4Þ

where AOp is measured in pascals or decibels, H and b are

the site factors, and SD is the scaled distance factor as

given in Eq. (3). The scaled distance factor is widely used

in surface blasting to predict AOp (Kuzu et al. 2009;

Hustrulid 1999). The site factor values, H and b, for dif-

ferent blasting conditions are tabulated in Table 2.

Hybrid PSO-based ANN

Many researches have been conducted to improve the

performance and generalization capabilities of ANNs. Or-

dinary ANNs employ the backpropagation (BP) algorithm

in the learning process, which is a local search learning

algorithm; therefore, the learning process of ANNs might

cause the convergence of the solution to fail (Liou et al.

2009). Since PSO is a robust global search algorithm, it can

be used to adjust the weights and biases of an ANN to

increase the performance and accuracy. The following

sections describe the procedure of ANN and PSO in

minimization problems and the implementation of hybrid

PSO-based ANN models.

Artificial neural network

An artificial neural network (ANN) can be identified as a

simplified mathematical model of reasoning based on the

human brain. ANN is able to determine the complex re-

lationship among variables for the simulation of one (or

more) output(s) (Specht 1991). A specific ANN model can

be defined using three important components: the transfer

Table 1 Empirical PPV

predictor presented by different

researchers

References Equation Site constant for granite

USBM by Duvall and Petkof (1959) v = K[R/HQMax]-B K: 179.31, B: 1.09

Langefors and Kihlstrom (1963) v = K[H(QMax/R2/3)]B K: 44.43, B: -1.18

General predictor by Davies et al. (1964) v = KR-B(QMax)A K: 212.27, B: 1.09, A: 0.52

Bureau of Indian Standard (1973) v = K[(QMax/R2/3)]B K: 6.33, B: 0.22

Ghosh–Daemen predictor (1983) v = K[R/HQMax]-Be-aR K: 780.36, B: 1.26, a: 0.0004

CMRI by Roy (1993) v = n ? K[R/HQMax]-1 K: 168.91, n: 1.57

v peak particle velocity (mm/s), Qmax maximum charge per delay (kg), R distance between blast face and

vibration monitoring point (m), (K, B, A, a, n) site constants

Table 2 Site factors H and bfor different blasting conditions

References Description H b

Siskind et al. (1980) Quarry blasts, behind face 622 0.515

Quarry blasts, direction of initiation 19,010 1.12

Quarry blasts, front of face 22,182 0.966

Hopler (1998) Confined blasts for AOp suppression 1906 1.1

Blasts with average burial of the charge 19,062 1.1

Hustrulid (1999) Detonations in air 185,000 1.2

Kuzu et al. (2009) Quarry blasts in competent rocks 261.54 0.706

Quarry blasts in weak rocks 1833.8 0.981

Overburden removal 21,014 1.404

Environ Earth Sci

123

function, network architecture, and learning rule (Simpson

1990). Based on the type of problem, these components

need to be defined as an initial set of weights and display

how weights should be modified during training to increase

the performance (Monjezi and Dehghani 2008). The mul-

tilayer perceptron (MLP) is one of the most well-known

feedforward neural network models and typically contains

an input layer of source neurons, at least one hidden layer

of computational neurons, and one output layer. Each of

these layers has its own specific function. The input layer

accepts inputs from the outside world and distributes them

to the subsequent layers. Features hidden in the input

patterns are detected by the neurons in the hidden layer.

The output layer exploits these features to determine the

output pattern (Bounds et al. 1998).

Several algorithms have been recommended for the

training of neural networks. The BP is the most popular

learning method among a vast number of MLP learning

algorithms (Basheer and Hajmeer 2000). In the BP method,

the input data are presented to the input layer to be

propagated through the network until an output is gener-

ated. Each neuron determines its net weighted input using

the following equation:

X ¼X

n

i¼1

xi wi�h; ð5Þ

where n is the number of inputs, and xi and wi denote the

values of the ith input and weight, respectively. The

threshold applied to the neurons is denoted by h. This input

value passes through one of the activation functions such as

a sigmoid, step, or linear function. Such a procedure is

technically known as a learning or training procedure. The

network computes its actual outputs, its weights, and a

mathematical function model threshold. Afterward, the

actual output is compared to the historical outputs to cal-

culate the output error (Rafiai and Jafari 2011). The ob-

tained error is propagated back through the network and

updates the individual weights. This process is called the

backward pass. This procedure is repeated until the error

reaches a defined level such as the mean square error

(MSE) (Simpson 1990; Kosko 1994). However, for train-

ing an ANN model, an experimental database requires an

appropriate number of datasets (Dreyfus 2005).

Particle swarm optimization

The particle swarm optimization (PSO) algorithm

originated from the social behavior of organisms (indi-

viduals) in swarms like flocks of birds (Kennedy and

Eberhart 1995). PSO is an evolutionary population-based

optimization technique that can be used to solve global

optimization problems within a nonlinear procedure. In

PSO algorithm, each particle denotes candidates’ solution

to the optimization problem. In this algorithm, particles

flow throughout the multidimensional search space to find

the best solution. Therefore, in each optimization problem,

several particles should be produced and scattered in the

search space. The particles change their positions in the

search space based on their experiences and those of

neighboring particles, and therefore the particles make use

of their own experience and those of their neighbors (En-

gelbrecht 2007). These particles form a population which is

technically known as a swarm.

Finding the best solution using PSO starts with initial-

ization of random particles (solutions) which are assigned

random positions and velocities. Subsequently, the algo-

rithm searches for the best solution through an iterative

procedure (Eberhart and Shi 2001). In the process each

particle keeps track of its best position, known as its per-

sonal best (pbest), as well as the overall best value accom-

plished by other particles in the swarm, known as the

global best (gbest).

Through the learning process, a particle’s journey to-

ward both the pbest and the gbest position is speeded up by

calculating a new velocity. The new velocity is calculated

in terms of the particle’s distance from the pbest and gbest

positions, which will affect the particle’s next position in

the next iteration.

A relatively simple procedure is required to obtain the

optimized solution using PSO as compared to the other

optimization algorithms (Van den Bergh and Engelbrecht

2000). In fact, PSO operates based on two simple equations

(Eqs. 6 and 7) for updating the particles’ velocities and

positions. To increase the convergence rate of the algo-

rithm, an inertia weight can be used in the original equa-

tions (Shi and Eberhart 1998), as in Eq. (6). The inertia

weight determines the rate of contribution of a particle’s

previous velocity to its current velocity:

vnew��! ¼ w � v~þ r1C1 � pbest

��!� p~� �

þ r2C2 � gbest��!� p~� �

;

ð6Þ

pnew��! ¼ p~þ vnew

��! ð7Þ

where vnew��! is the new velocity and w is the inertia weight.

v~, pnew��!, and p~ are the current velocity, new position, and

current position of particles, respectively, C1 and C2 are

acceleration constants, pbest��! is the personal best position of

the particle, gbest��! is the globally best position among all

particles, and r1 and r2 are random values in the range (0,

1) sampled from a uniform distribution.

PSO-based ANN algorithm

Many attempts have been made to improve the ANN per-

formance by means of optimization algorithms, due to the

Environ Earth Sci

123

fact that an optimum search process of conventional ANNs

might fail and return an unsatisfactory solution (Liou et al.

2009; Engelbrecht 2007). Several studies have been con-

ducted to investigate the ability of PSO as a training al-

gorithm for a number of different ANN architectures.

Eberhart and Kennedy (1995) presented the first results of

utilizing the basic PSO to train ANNs, whereas several

scholars have further demonstrated the capability of PSO in

training ANNs and showed that the PSO is an effective

alternative for training ANNs (Mendes et al. 2002; Settles

and Rylander 2002; Gudise and Venayagamoorthy 2003).

It should be noted that further attempts have been made to

employ other optimization techniques in training ANNs,

for example, genetic algorithm and ant colony optimization

techniques (Montana and Davis 1989; Socha and Blum

2007). Nevertheless, it has been proven that ANNs trained

by PSO provide more accurate results compared to other

learning algorithms (Engelbrecht 2007).

In ANN training, a set of weights and biases are deter-

mined which minimize an objective function such as MSE.

So, MSE can be used as the fitness function in training an

ANN using PSO, due to the fact that a fitness function is

required to generate a PSO-based ANN model.

In a minimization problem, there is one global minimum

and a number of local minima. ANN searches for a solution

in the local region due to its inherent property and therefore

usually gets trapped in a local minimum. PSO has a com-

petent capability to search the entire search space to find the

global minimum and continues searching around it. Hence,

a hybrid PSO-based ANN model has the search properties

of both PSO and ANN, where PSO looks for the global

minimum in the search space and ANN uses the global

minimum to find the best results (Gordan et al. 2015).

The learning process in a PSO-based ANN model is

initialized by generating a group of random particles in

which each particle represents a set of weights and biases

in the model. The PSO-based ANN model is trained using

the initial weights and biases (i.e., initial position of par-

ticles), the particle’s velocity and position are updated

using the PSO equations, and subsequently, in each it-

eration, the weights and biases of the model are adjusted. In

each iteration, the MSEs between the actual and predicted

values are calculated and the errors are reduced by

changing the positions of the particles. This process is

continued to find the best weights and biases for an ANN to

minimize the error function.

Case study and data collection

This study was conducted at Hulu Langat quarry site in

Selangor State, Malaysia. Geographically, the quarry lies at

a latitude of 3�70000N and a longitude of 101�490100E and is

located in the south of Selangor. An overall view of the

Hulu Langat quarry site is shown in Fig. 2. This quarry is

composed of granitic rocks with the capacity to produce

large amounts (between 280,000 and 360,000 tons per

month) of aggregate. Blasting is carried out 10–12 times

per month, depending on the weather conditions. All

blasting operations are conducted using blastholes 89 mm

in diameter. Ammonium nitrate and fuel oil (ANFO) and

dynamite were used as the main explosive material and for

initiation, respectively. The blastholes were stemmed using

fine gravels.

During 9 months from August 2012 to April 2013, 88

datasets were collected. During data collection, blasting

parameters including hole depth, maximum charge per

delay, burden, spacing, stemming length, sub-drilling,

powder factor, and number of holes were obtained. In each

blast, PPV and AOp values were recorded using a Vi-

braZEB seismograph. In the case of AOp, the values were

monitored during each blasting operation using linear L

type microphones connected to the AOp channels. A range

of AOp values from 88 dB (7.25 9 10-5 psi or 0.5 Pa) to

148 dB (0.0725 psi or 500 Pa) can be recorded by Vi-

braZEB. The microphones have an operating frequency

response from 2 to 250 Hz, which is adequate for mea-

suring AOp accurately in the frequency range critical for

structures and human hearing. All AOp and PPV values

were recorded in front of the quarry bench and ap-

proximately perpendicular to it.

The crushing plant and workshops are located about

400 m to the southwest of the quarry face, while the

nearest residential area is about 800 m to the west of the

quarry face. Therefore, the distance between the monitor-

ing point and free face was set as 300, 600, and 700 m.

Figure 3 shows the location of the quarry site and nearest

residential area.

The use of the SD is a common technique to predict PPV

and AOp values resulting from blasting. The relationships

between the SD and the two parameters of distance and

explosive charge weight per delay are formulated as fol-

lows for PPV prediction (Duvall and Petkof 1959):

SD ¼ DW�0:5; ð8Þ

where W is the maximum charge per delay (kg) and D

represents the distance between the monitoring point and

free face (m). The correlation of maximum charge weight

per delay, distance, and SD is given in Eq. (3) for AOp

prediction. Afterward, PPV and AOp values can be deter-

mined using the USBM-suggested equation as follows:

PPV=AOp ¼ KðSDÞB; ð9Þ

where B and K are site constants. The graphs of the mea-

sured PPV and AOp values against their SDs are shown in

Figs. 4 and 5, respectively. In addition, two empirical

Environ Earth Sci

123

equations were proposed for the prediction of PPV and

AOp values as indicated in these figures. Coefficient of

determination R2 values equal to 0.581 and 0.410 for PPV

and AOp prediction suggest that the proposed equations

can predict them with good accuracy level.

Development of PSO-based ANN model for PPVand AOp prediction

A MatLab code was developed to predict PPV and AOp

using a hybrid PSO-based ANN model. ANNs work based

on given data and do not have previous knowledge about

the subject of prediction. Therefore, to predict the PPV and

AOp induced by blasting, all relevant parameters should be

determined. The following sections describe the develop-

ment procedure of a PSO-based ANN model to predict the

PPV and AOp induced by blasting.

Input and output parameters

Determining the input parameters is the first step of de-

veloping a prediction model for PPV and AOp. To develop

a comprehensive and accurate model, the parameters with

the greatest influence on PPV and AOp should be deter-

mined. In determining the influential parameters, it should

be considered that the selected parameters must represent

the site conditions as well as the blast design parameters,

Fig. 2 A view of the Hulu

Langat granite quarry site

Fig. 3 Location of the quarry site and the nearest residential areas

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123

must be measurable, and must be easy to obtain

concurrently.

A direct relationship exists between the blast design

parameters and the PPV and AOp values in blasting op-

erations. Therefore, the blast design parameters including

hole depth, maximum charge per delay, burden-to-spacing

ratio, stemming length, sub-drilling, powder factor, and

number of holes were taken into account in modeling. The

values of PPV and AOp may increase if the design of these

parameters is carried out improperly.

Geological discontinuities, in addition to the aforemen-

tioned parameters, have a significant impact on PPV and

AOp in blasting operations. In the presence of geological

discontinuities, explosive gases escape intensely from the

discontinuities, leading to high vibration magnitudes.

Therefore, as a degree of jointing or fracturing in a rock

mass, the rock-quality designation (RQD) was used in

modeling to represent the geological discontinuities.

It is obvious that the PPV and AOp values decrease as

the distance between the free face and the monitoring point

increases. Therefore, as an influential parameter, this pa-

rameter was used in modeling. Table 3 shows the input and

output parameters and their ranges. The modeling proce-

dure was started by normalization of the input and output

data. It is recommended that the input and output data be

normalized before they are presented to the network. Ac-

cording to Rafig et al. (2001), normalization helps to im-

prove the learning speed of the network. By using the

following equation, the data were normalized into a range

of -1 to 1.

xN ¼ x�Min x

Max x�Min x

� �

�2� 1; ð10Þ

where xN is the normalized value of the variable x, and Min

x and Max x are the minimum and maximum values, re-

spectively, for the variable x.

Fig. 4 Relationship between

scaled distance and PPV values

Fig. 5 Relationship between

scaled distance and AOp values

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123

Network design

A PSO-based ANN model performs best when its pa-

rameters are selected properly. The PSO parameters (in-

cluding number of particles, acceleration constants for

gbest (C1) and pbest (C2), and inertia weight) as well as the

ANN parameters (network architecture including the

number of hidden layers and the number of nodes in a

hidden layer) are related to the performance of the PSO-

based ANN model. Therefore, many computations were

conducted to determine the optimal configuration of the

PSO-based ANN model. A series of sensitivity analyses

was conducted to find the optimum PSO parameters.

Subsequently, the optimum network architecture was de-

termined using the trial and error method as well as the K-

fold cross-validation technique.

PSO parameters

A MatLab code was developed to perform the sensitivity

analyses. These analyses consist of several independent

steps to determine the optimum number of particles, ac-

celeration constants, and inertia weight. The performance

of PSO-based ANN models in minimizing the MSE was

evaluated during the sensitivity analyses.

As an initial model, a PSO-based ANN model consisting

of a single hidden layer with nine nodes was used. For each

analysis, 80 % of the data was assigned for training while

the remaining 20 % was used for testing. Each analysis was

conducted three times and the best value was selected as

the representative value of the model.

To obtain the appropriate number of particles in the

swarm (swarm size), a series of sensitivity analyses was

applied to the PSO swarm size because no other method of

finding the optimum swarm size exists. While a small

swarm may fail to converge to a global solution, a large

swarm may lead to delay in the convergence and decrease

the efficiency. The analyses were performed by setting a

fixed iteration number of 1000 for each model with various

numbers of particles and a fixed value of 2 for both ac-

celeration constants, C1 and C2. R2 and MSE are the model

selection criteria. Figure 6 illustrates the results of the

sensitivity analyses for the number of particles.

According to Fig. 6a, in general, the values of R2 have

been increased by increasing the number of particles.

However, after a significant increase in the values of R2

Table 3 Input and output

parameters used in the

prediction model

Parameter Category Unit Symbol Minimum Maximum Average St. deviation

Hole depth Input (m) A 10 17 14.4 2.28

Charge per delay Input (kg) B 56.3 101.6 84.5 14.27

Burden to spacing Input – C 0.7 0.92 0.8 0.06

Stemming length Input (m) D 1.9 3.6 2.7 0.43

Sub-drilling Input (cm) E 25 45 35.3 6.71

Powder factor Input (kg/m3) F 0.4 1.18 0.9 0.22

RQD Input (%) G 41 77 59.4 10.81

Distancea Input (m) H 300 700 553.3 129.46

Number of holes Input – I 15 63 38.1 11.01

Peak particle velocity Output (mm/s) PPV 1.1 9.5 3.5 2.21

Air overpressure Output (dB) AOp 90 127 105.4 10.49

a Distance between free face and monitoring point

Fig. 6 a R2 for models with different swarm size, b MSE for models

with different swarm sizes

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when the number of particles increased from 10 to 250, the

network performance does not improve afterward. The

same results were obtained between the number of parti-

cles and the values of MSE, as shown in Fig. 6b. Mean-

while, the training time was gradually increased by

increasing the number of particles, as shown in Fig. 7. As

a result, a swarm size of 250 was selected as the optimum

number of particles to avoid ineffectual iterations in the

models.

The next sensitivity analyses were conducted to deter-

mine the optimum values of the acceleration constants, C1

and C2. A series of candidate combinations were used

based on the original (Kennedy and Eberhart 1995) and

modified (Clerc and Kennedy 2002) acceleration constants,

as shown in Table 4. The analyses were conducted using

the obtained optimum swarm size of 250 on the initial

network, including a single hidden layer with nine nodes.

The results of the sensitivity analyses are shown in Table 4.

Superior results were obtained by model number 3 com-

pared to other models, as it had the highest values of R2 and

the lowest values of MSE for the training and testing

datasets. As a result, the values of 1.714 and 2.286 were

selected for acceleration constants C1 and C2 to be used in

the prediction of PPV and AOp.

The next step in designing an optimum network is

finding an appropriate inertia weight. Based on the inertia

weight suggested in previous studies (Shi and Eberhart

1998; Clerc and Kennedy 2002), four tests with different

inertia weights were designed to find the optimum value of

the inertia weight in the PSO equation. The same initial

swarm with a size of 250 was applied in all the tests, and

the acceleration constants were set at the previously de-

fined optimum values of 1.714 and 2.286 for C1 and C2,

respectively. Figures 8 and 9 show the values of R2 and

MSE for the training and testing datasets at different inertia

weights. According to these figures, the highest R2 and the

lowest MSE for the training and testing datasets were ob-

tained at an inertia weight of 0.5. Hence, this value was

selected as the optimal inertia weight.

Network architecture

PSO can only adjust the weights and biases of a model to

minimize the learning error. Therefore, the network ar-

chitecture, composed of the number of hidden layer(s) and

the number of nodes in each hidden layer, should be de-

termined through the trial and error method as a conse-

quence of the fact that there is no absolute method of

determining the optimum network architecture.

Following the determination of the PSO parameters, the

optimal network architecture was obtained. This was done

through the trial and error method. A K-fold cross-valida-

tion technique (Diamantidis et al. 2000) was employed to

evaluate the performance of each model. In this technique,

the data are divided into K parts, of which K - 1 parts are

used for training and one part is used to test the model. The

process is repeated K times and therefore all of the data are

used in the training and testing steps.

To determine the optimal network architecture, 14

hybrid models were considered and a fivefold cross-

validation was used to evaluate the performance of the

models. Each model was trained with fourfold cross-

Fig. 7 Training consumed time for models with different swarm

sizes

Table 4 The results of

sensitivity analyses for

acceleration constants

C1 and C2

Model Relationship C1 C2 C1 ? C2 Training Testing

R2 MSE R2 MSE

1 C1 = 0.25 C2 0.8 3.2 4 0.73 0.141 0.66 0.195

2 C1 = 0.5 C2 1.333 2.667 4 0.85 0.085 0.83 0.086

3 C1 = 0.75 C2 1.714 2.286 4 0.89 0.056 0.88 0.072

4 C2 = 0.25 C1 3.2 0.8 4 0.70 0.155 0.70 0.150

5 C2 = 0.5 C1 2.667 1.333 4 0.72 0.180 0.72 0.142

6 C2 = 0.75 C1 2.286 1.714 4 0.81 0.112 0.80 0.092

8 C1 = C2 2 2 4 0.79 0.120 0.77 0.112

9 C1 = C2 1.75 1.75 3.5 0.75 0.122 0.74 0.124

10 C1 = C2 1.5 1.5 3 0.67 0.201 0.66 0.159

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validation (70 datasets) and tested with the rest of the data

(18 datasets). Therefore, each model was trained and

tested five times with different combinations of training

and testing datasets. The values of Rave2 and MSEave for

the testing datasets were considered as the model per-

formance criteria.

The processes were conducted with different numbers of

hidden layers in the networks and various numbers of

nodes in each hidden layer. Hidden layers of one and two

layers were considered to find the optimum number of

hidden layer(s) and 6, 9, 12, 15, 18, 21, and 24 nodes were

considered to find the optimum number of nodes in each

hidden layer. All models were trained with the optimized

PSO parameters obtained in previous analyses. The results

of the analyses are tabulated in Table 5.

Figures 10 and 11 display the values of Rave2 and MSEave

for trained models with different architectures. According

to the figures, model number 3 presents the best perfor-

mance in terms of values of Rave2 and MSEave for the testing

datasets among all models: 0.89 for Rave2 and 0.038 for

MSEave. Therefore, the architecture of model number 3

was selected as the optimum architecture. The structure of

the selected PSO-based ANN model consisting of one

hidden layer and 12 nodes in the hidden layer is illustrated

in Fig. 12.

Analysis of the results

A graphical comparison between the measured and pre-

dicted values of PPV and AOp employing different

training datasets is shown in Fig. 13. According to the

figure, a superior concordance exists between the mea-

sured and predicted values of PPV and AOp. This is

because of the capability of PSO to minimize the error

Fig. 8 R2 for training and testing datasets at different inertia weights

Fig. 9 MSE for training and testing datasets at different inertia

weights

Table 5 Performance of trained PSO-based ANN models

Model Network architecture Train Test

hidden layers Nodes in hidden layers R2 MSE R2 MSE

Min Max Ave Min Max Ave Min Max Ave Min Max Ave

1 1 6 0.70 0.82 0.76 0.133 0.167 0.146 0.66 0.82 0.74 0.112 0.166 0.143

2 1 9 0.81 0.89 0.85 0.056 0.130 0.097 0.80 0.88 0.84 0.072 0.090 0.088

3 1 12 0.80 0.95 0.89 0.014 0.060 0.034 0.85 0.94 0.89 0.029 0.050 0.038

4 1 15 0.82 0.95 0.86 0.033 0.110 0.089 0.84 0.92 0.88 0.065 0.104 0.071

5 1 18 0.83 0.91 0.86 0.056 0.115 0.090 0.87 0.90 0.89 0.052 0.110 0.073

6 1 21 0.79 0.86 0.83 0.085 0.128 0.104 0.75 0.85 0.81 0.095 0.137 0.114

7 1 24 0.73 0.83 0.78 0.106 0.160 0.136 0.72 0.80 0.75 0.125 0.146 0.136

8 2 6 0.68 0.80 0.73 0.141 0.167 0.141 0.64 0.75 0.68 0.157 0.203 0.169

9 2 9 0.67 0.80 0.75 0.090 0.188 0.143 0.72 0.80 0.75 0.111 0.135 0.122

10 2 12 0.82 0.87 0.85 0.069 0.103 0.089 0.75 0.85 0.80 0.081 0.152 0.121

11 2 15 0.73 0.82 0.78 0.109 0.162 0.132 0.75 0.81 0.78 0.094 0.148 0.118

12 2 18 0.66 0.75 0.71 0.098 0.207 0.146 0.69 0.79 0.72 0.120 0.212 0.167

13 2 21 0.67 0.78 0.72 0.118 0.162 0.145 0.63 0.76 0.70 0.139 0.178 0.158

14 2 24 0.65 0.72 0.70 0.148 0.179 0.164 0.68 0.71 0.69 0.165 0.176 0.168

Environ Earth Sci

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function with high efficiency; the PSO algorithm adjusts

the weights and biases of the error objective function of

ANN to obtain the minimum MSE. The same results were

obtained for the testing datasets, as can be seen in

Fig. 14. As shown in the figure, the predicted values of

PPV and AOp obtained by employing the proposed PSO-

based ANN model are in close agreement with the mea-

sured values. It is worth noting that the results of the

optimum PSO-based ANN model presented in these fig-

ures are the best obtained by model no. 3, whereas the

results tabulated in Table 5 are the average values of five

repeated runs.

PPV and AOp prediction through PSO-based ANNmodel and empirical approaches

A comparison was conducted between the values of PPV

and AOP predicted by the proposed PSO-based ANN

model, empirical approaches, and measured values to

check the accuracy of the proposed model. For this pur-

pose, ten datasets were selected in terms of the distance

between the free face and the monitoring point, rock

properties, and blasting parameters, as listed in Table 6.

Figure 15 shows a comparison between the measured

PPV and predicted PPV values obtained by empirical

Fig. 10 Rave2 for trained PSO-based ANN models

Fig. 11 MSEave for trained

PSO-based ANN models

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Fig. 12 Structure of the

selected PSO-based ANN model

to predict PPV and AOp

induced by blasting

Fig. 13 Comparison between measured and predicted a PPV and b AOp for different training datasets

Environ Earth Sci

123

approaches (see Table 1) and the proposed PSO-based

ANN model. It can be seen that the PPV values obtained

by the PSO-based ANN model are in very good agree-

ment with the measured values, whereas there are wide

variations in PPV values predicted by empirical methods.

For the selected datasets, AOp values were obtained by

means of empirical approaches (Eqs. 1, 2, and 4). Based on

the site conditions, three different sets of site factors

(H = 22,182 and b = 0.966; H = 19,062 and b = 1.1;

H = 261.54 and b = 0.706) were extracted from Table 2.

Fig. 14 Comparison between measured and predicted a PPV and b AOp for different testing datasets

Table 6 Investigated parameters to estimate PPV and AOp by PSO-based ANN model and empirical approaches

No. Hole

depth (m)

Charge per

delay (kg)

Burden to

spacing

Stemming

length (m)

Sub-drilling

(cm)

Powder factor

(kg/m3)

RQD

(%)

Distance

(m)

No. of

holes

2

10

57.8 0.79 2 25 0.42 76 600 43

9

10.8

64.2 0.81 1.9 30 0.67 70 700 24

14

11.3

60.4 0.82 2.9 30 0.56 76 700 41

26

13.3

77.0 0.81 2.7 28 0.83 61 600 56

39

14.9

85.6 0.70 3.1 33 1.01 76 600 39

45

15.2

87.7 0.81 3.1 35 0.99 57 600 37

49

15.5

90.3 0.81 3 40 1.04 56 600 39

70

16.5

94.8 0.78 3.4 40 1.16 49 600 35

78

16.6

97.5 0.80 3.1 43 1.04 69 300 42

85

17

98.9 0.75 3.3 44 1.17 48 300 39

Environ Earth Sci

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Subsequently, a comparison was made between the mea-

sured AOp values and predicted AOp values obtained by

the PSO-based ANN model and empirical approaches, as

shown in Fig. 16. According to the figure, the proposed

PSO-based ANN model yields more accurate results

compared to empirical approaches. Based on Figs. 15 and

16, it can be concluded that the proposed PSO-based ANN

model is an applicable tool for the prediction of PPV and

AOp induced by blasting of this quarry with a high degree

of accuracy.

Fig. 15 Comparison of PPV for selected datasets

Fig. 16 Comparison of AOp for selected datasets

Environ Earth Sci

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Sensitivity analysis

A sensitivity analysis was carried out to identify the rela-

tive influence of each parameter in the neural network

system by the cosine amplitude method (Yang and Zang

1997). To apply this method, all data pairs were expressed

in common X-space. The data pairs used to construct a data

array X are defined as:

X ¼ x1; x2; x3. . .; xi; . . .; xnf g:

The elements xi in the array X are a vector of length m, that

is:

xi ¼ xi1; xi2; xi3. . .; ximf g:

Each of these data pairs can be trained as a point in m-

dimensional space, where each point requires m-coordi-

nates for a full description. Thus, in the space pair, all the

points are associated with the achieved results. The fol-

lowing equation illustrates the strength of the relation (rij)

between the dataset Xi and Xj:

rij ¼Pm

k¼1 xikxjkffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

Pmk¼1 x2

ik

Pmk¼1 x2

jk

q : ð11Þ

Table 7 shows the strengths of the relations (rij values)

between the input and output (PPV and AOp) parameters.

The sensitivity analysis results show that sub-drilling

(E) and maximum charge per delay (B) are the parameters

with the greatest influence on PPV, whereas stemming

length (D) and maximum charge per delay (B) are the

parameters with the greatest influence on AOp.

Conclusion

A MatLab code was developed to predict blast-induced

PPV and AOp using a hybrid PSO-based ANN model.

Eighty-eight datasets collected from Hulu Langat granite

quarry site in Malaysia were used to develop an optimum

PSO-based ANN model. Hole depth, maximum charge per

delay, burden-to-spacing ratio, stemming length, sub-dril-

ling, powder factor, RQD, distance between the free face

and the monitoring point, and number of holes were used as

input parameters, while PPV and AOp values were set as

output parameters. A series of sensitivity analyses were

conducted to determine the optimum PSO parameters. The

optimum network architecture was determined following

the trial and error method. Finally, a model with one hidden

layer and 12 nodes in the hidden layer was selected to be

used for prediction. A comparison was made between the

results obtained by the PSO-based ANN model and em-

pirical predictors as well as the measured values to examine

the applicability and accuracy of the proposed model. The

results indicate that the proposed PSO-based ANN model is

practically able to predict PPV and AOp induced by blast-

ing in granite quarry sites with similar conditions. Through

the sensitivity analyses, it was also found that the sub-

drilling and maximum charge per delay are the parameters

with the greatest influence on PPV, whereas the stemming

length and maximum charge per delay are the parameters

with the greatest influence on AOp.

Acknowledgments The authors would like to extend their appre-

ciation to the Universiti Teknologi Malaysia for UTM Research

University Grant No. 01H88 and for providing the required facilities

that made this research possible.

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Table 7 Strengths of relation

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