ASSESSMENT AND APPLICATION OF A SINGLE-CHARGE 

BLAST TEST AT THE KIRUNA MINE, SWEDEN 

D.R. Tesarik1, W.A. Hustrulid2

1, 2 NIOSH, Office of Mine Safety and Health Research, 315 E. Montgomery Ave, Spokane, WA 99207; 1

D.R. Tesarik, det4@cdc.gov; 2W.A. Hustrulid, bet1@cdc.gov
�

& U. Nyberg3 

3 Division of Mining and Geotechnical Engineering, Lulea University of Technology, SE-971 87 Lulea, 

Sweden; ulf.nyberg@ltu.se
�

ABSTRACT 

Peak particle velocity (PPV) and distance measurements from a single-charge 

blast test conducted by Swedish researchers in iron ore at the Kiruna Mine in northern 

Sweden are presented. They are used along with theoretical PPVs calculated using an 

equation based on hydrodynamics to determine a damage distance range caused by a 

single charge. This equation, which relates PPV to explosive properties, charge geometry, 

and distance from a charge, was then applied to a charge of different geometry that was 

used in drift rounds. A comparison between calculated and measured PPVs suggests that 

the stoping holes likely damage the easer hole locations, and the easer holes produce 

damage to the perimeter hole locations. The practical effect is that typical damage limit 

predictions based on measurements conducted in fresh or undamaged rock are 

conservative. This suggests that even when perimeter control is not exercised in drifting 

(i.e., the perimeter holes are fully loaded), the resulting damage may be less than 

normally expected due to the wave damping effect of the pre-damaged rock. Due to the 

damping effect, poor perimeter blasting practices are somewhat self correcting. However, 

it must be strongly emphasized that well-engineered blast designs with perimeter control 

are highly beneficial in relation to both economic and safety aspects. 

1. INTRODUCTION 

Blast damage around excavation perimeters is a contributing factor to injuries 

caused by rockfalls in underground mines. This unwanted perimeter damage also results 

in extra time required to scale and install supports under potentially hazardous ground 

conditions. By implementing controlled blasting, perimeter damage can be minimized 

and underground safety improved. Methods, such as line drilling, presplitting, cushion 

blasting, fracture control blasting, and smooth blasting are successfully used in civil 

tunneling operations (Lizotte 1994, Olofsson 1990); but, they are less often used in the 

mining industry because of perceived additional costs and the expected life of 

underground openings is generally much less than that of civil structures. However, when 

carefully looking at the complete cost/benefit picture regarding perimeter control blasting 

in drift driving, it is clear that the contribution of perimeter control is economically 

desirable (Miller & Camm 2009). Additional drilling and blasting costs are balanced by 

reduced dilution, less scaling time and support requirements, less ground rehabilitation 

costs, and other items. An additional benefit of prime concern to the National Institute for 
Occupational Safety and Health (NIOSH) is the increase in personnel safety achieved by 

reducing exposure to loose material in the perimeter of a mine opening. 

A commonly applied approach for perimeter control blast design was developed 

by Holmberg and Persson (1979). It is based on the peak particle velocity (PPV) 

generated at a certain distance away from a charge of known explosive weight. The 

limiting PPV value is the velocity associated with the extent of the damage zone. In 

practice, the damage zone limit is identified by various methods including visual, shear or 

p-wave velocity measurements, core strength determinations as a function of distance 

away from the blasthole, and other methods (Iverson et al. 2009). Several other perimeter 

blast design approaches use PPV as a measure of damage. These include work by 

Hustrulid et al. (1992), who developed a PPV dampening law based on the calculated 

pressure in the blasthole, and Blair and Minchinton (2006), who developed the Scaled 

Heelen model which uses linear waveform superposition to calculate particle velocity at a 

given point. Blair also used nonlinear superposition to calculate blast vibration for both 

single charges and full-scale blasts (Blair 2008). Neiman and other Russian researchers 

applied hydrodynamic theory to develop a relationship between PPV, rock and explosive 

parameters, and charge geometry (Neiman 1976, 1979, 1984a, 1984b, 1986a, 1986b). A 

summary of their work is presented by Hustrulid (1999). 

This paper uses equations developed by Neiman as well as PPV and distance 

measurements collected by Swedish researchers (Nyberg 1998, Jinnerot and Nilsson 

1998) to analyze damage around individual charges. The field tests were conducted 

jointly by the Swedish Rock Research Foundation (SveBeFo) and LuossavaaraKiirunavaara Aktiebolaget (LKAB) at LKAB's Kiruna Mine in Northern Sweden. The 

overall objective of the field study was to develop a basis for more effective drift driving 

in varying geological conditions. The immediate aim was to reduce damage to the 

perimeter and overbreak and, consequently, reduce scaling and reinforcement 

requirements. 

2. KIRUNA MINE 

LKAB's Kiruna Mine is located in the rich iron ore fields of northern Sweden. 

LKAB started mining the fine-grained magnetite ore in the late 1800s using open pit 

methods and switched to underground methods in the 1950s. Today, the primary method 

of mining is sublevel caving (Lupo 1997). 

The ore body is approximately 4 km long with an average width of 85 m and an 

estimated depth of 2 km. It dips at about 60o

 to the east and plunges to the north. 

The main level lies 1,045 m below the surface and mining takes place between the 775- 

and 1,045-m levels. The mine produces about 26 million tons of crude ore per year 

(www.LKAB.com 2010). 

The footwall consists of either trachite or rhyolite with layers of trachite. The 

rock in the hanging wall is rhyodacite with dikes of diabase and porphyry. The shears in 

the ore body are filled with calcite or pyrite. The joints are tight but numerous, sometimes 
 

having a thin hematite coating. Some crushing and clay alteration has been encountered 

in core recovered from diamond drill holes (Nyberg et al. 1998). Material properties for 

the magnetite are listed in Table I. 

Material Property Value 

Compressive strength 115 MPa 

Density 4,800 kg/m3 

Seismic velocity, across drifts (N-S) 4,880 m/s 

Seismic velocity, along drifts (E-W) 6,273 m/s 

Table I- Material properties for the Kiruna ore (Nyberg et al. 1998) 

3. VELOCITY EQUATIONS FOR A CYLINDRICAL CHARGE 

3.1 Theoretical background 

Neiman (1976, 1979, 1984a, 1984b, 1986a, 1986b) used hydrodynamic principles 

to develop equations (1 - 3) that express the velocity components at a given location 

from a detonating cylindrical charge as a function of specific density of the explosive, 

energy per unit mass of the explosive, specific density of the rock, geometry of the 

charge and the three Cartesian coordinates at the specified location from the charge. 

Figure 1 shows a diagrammatic representation of the geometry to be used (Hustrulid 

1999). 

l = Px(AB - CD)

Figure 1- Cylindrical charge with coordinate axes origin at centroid of charge. 

 ' (1) 
 

 (2) 

 (3) 

 

 

A = (4) ' ( )

 (5) ' ( )

 

 C = (6) ' ( )

 (7) ' ( )

 

 

P = dJ (8)

 

 

 v = 1n ( LL

 LL 

V

V 

LL

LL ) (9) s

 -L = L (10) ­

 PPl = Jl' 

2 + l 2 + l 2 (11) 

 

 = (12) 

 

 

 

l =Py(AB - CD)

l = Pz(C - A)

where: 

B =

D =

 pe = density of the explosive 

qe =specific energy of the explosive 

pr =density of the rock 

z1, z2 = z coordinates at charge ends 

x y, z = , coordinates of the point in question

d = hole diameter 

L = charge length 

The PPV is defined as 

Equation (12) is the expression for the theoretical radial velocity, ut, along the x axis for a 

cylindrical charge of length L and diameter d: 

where 
 

 

 

 = J (13) 

 

 

r Jr	� gL

4 = (14) LL

 

 r = the distance along the x axis. 

 

 

r _ = 

­

The explosive parameters are contained in the multiplying constant I. The charge 

geometric terms are contained in the parameter Gt. Neiman used the symbol p to 

represent this parameter (Hustrulid 1999). It has been changed to Gt in this paper to avoid 

confusion with the symbol p used in conjunction with rock and explosive density. 

Neiman (1979) has shown that the equation for measured radial velocity, uf, from 

field tests has the same form as equation (12) where If and a are determined from 

measured data: 

 

 = (15) 

 

 

 

 

Equation (15) can be used to assess the extent of damage from single charges if the 

critical PPV and the values of If and a have been determined by field measurements. In 

general, measured PPVs are less than theoretical PPVs because of discontinuities in the 

rock mass. 

3.2. Modification of the experimental velocity expression for a different explosive 

Equation (15) is valid only for the rock mass in which the test was conducted and 

for the explosive that was used during the collection of the velocity and distance 

measurements. However, this equation can be modified to account for different 

explosive properties and eliminate the need to conduct additional blasting tests in the 

given rock mass. 

If different explosive properties produce a different value of I, equal to I

 '

, then the 

theoretical particle velocity is 

 

 = I (16) 

Solving for Gt in equation (12) yields: 

 

 

= (17) 
Substituting this expression for Gt into equation (16), the expression for the theoretical 

velocity, which now applies when an explosive with different properties is used, becomes 

 

 

 

 

I = (18) 

If it is assumed that the field velocities are changed by the same ratio as the theoretical 

velocities when h lt e exp osion term is changed, the equation for field velocity becomes 

 

 

 

 

 I = (19) 

3.3 Modification of the velocity expression to include decoupling 

To account for decoupling, one approach is to modify the specific density of the 

explosive by distributing the weight of the explosive over the volume of the hole. 

For example, b a ec use the specific density of the explosive is 

 

 Pe = W (20) r L

where we is the weight of the explosive and re is the radius of the charge, the weight of 

the explosive can be written as 

 e = Pe _ 2- (21) e

The weight of the explosive per unit volume of the hole is 

 

 

Pe = r L (22) r L 

 

where rh is the radius of the hole. 

Simplifying equation (22) yields 

r (23)

 

Pe = Pe ( )2

r

 

 

 

 

Replacing the specific explosive density term pe in equation (13) by the modified 

expression pe given by equation (23) and simplifying yields 

 

 

= r

r J (24) 

Equation (24) implies that decoupling will reduce particle velocity by the ratio re/rh. 
 

4. FIELD TESTS 
�

4.1 Background 

Two series of single-charge tests and a series of drift round tests were conducted 

in magnetite ore on the 792 m level at the southern end of the Kiruna Mine by researchers 

from SveBeFo and LKAB. A plan view of the overall test arrangement is shown in 

Figure 2. Particle velocity measurements for the single-charge test analyzed in this study, 

called Zero Test 2, and the drift rounds were measured using accelerometers installed in 

holes drilled from Drift 408 toward Drift 406. The acceleration signals were logged and 

then integrated to obtain PPV values. The first maximum PPV value in the wave train 

was used based on findings by Bjarnholt and Skalare (Bjarnholt and Skalare 1981). Saw 

cuts were made in the ribs of the Drift 406 at several locations after blasting the drift 

rounds to assess the extent of rock damage. The overall objective was to relate the PPV to 

the damage distance from the contour charge. 

In this paper, velocity and distance measurements from Zero Test 2 along with 

theoretical PPVs calculated using Neiman's equations are used to determine a damage 

range caused by a single charge. The relationships developed based on the data collected 

from Zero Test 2 are then used to analyze the damage caused by the stoping, easer, and 

perimeter holes in two of the drift rounds. 

4.2 Zero Test 2 

Zero Test 2 consisted of single charges detonated individually in 5-m-long holes 

drilled into the face of Drift 406 as shown in Figures 3 and 4. All together, 12 single-shot 

charges were detonated. Of these, only 5 produced usable results because the particle 

velocities produced by primer or detonating cord charges used in some of the blasts were 

too small to measure. In this paper, the focus is on the results obtained with blasting 

fully-coupled charges (Holes 1, 2, and 3) containing the repumpable emulsion explosive 

Kimulux R. Blasthole 1 had a diameter of 100 mm, blasthole 2 a diameter of 76 mm and 

blasthole 3 a diameter of 64 mm. The three holes were shot sequentially in different 

blasts beginning with hole 1. The bottom end of each of the charges in holes 1, 2, and 3 

was approximately 2 m from the bottom of the blastholes. Blast initiation was at the end 

of the charge. Blastholes 4 and 5 were used for single-shot decoupled charges. The 

explosive, blasthole diameter, charge diameter, and charge length used are listed in Table 

II. The explosive properties are listed in Table III. 
Figure 3- Plan view of Zero Test 2.

Figure 4- Elevation view of Zero Test 2 at Drift 406 face.

 

The measurement holes were drilled perpendicular to the blast holes from Drift 

408 and were located approximately in the same plane as the blastholes. Threedirectional accelerometer readings were recorded in the measurement hole closest to the 

blastholes; otherwise, the measurements were bidirectional. 
 

Blasthole Shot Explosive Blasthole 

diameter 

(mm) 

Charge 

diameter 

(mm) 

Charge 

length (m) 

1 1 KRa 100 100 0.480 

2 1 KR 76 76 0.490 

3 1 KR 64 64 1.100 

4 1 K42b 48 22 0.682 

4 2 K42 48 22 0.682 

5 1 K42 48 22 0.682 

5 2 K42 48 22 0.682 a

Kimulux R 

b

Kimulux 42 

Table II- Explosive, blasthole diameter, and charge geometry for Zero Test 2 (Nyberg et 

al. 1998) 

Explosive Kimulux R Kimulux 42 

Weight strength (%) 81 90 

Volume strength (%) 115 114 

Density (kg/m3

) 1,200 1,100 

Velocity of detonation (m/s) 5,500 5,000 

Gas volume (l/kg) 906 874 

Energy (MJ/kg) 2.94 3.35 

Detonation pressure (GPa) 9.1 6.8 

Table III- Explosive properties (Nyberg et al. 1998) 

The results from the fully coupled charge (shots 1-3) tests 

• distance from the charge 

• measured PPV 

• theoretical PPV using equations (1-11) 

are listed in Table IV. The three-dimensional equations for PPV were used because the 

accelerometers were not located exactly on the x axis of the charges which is required for 

equation (12). 

 
Blasthole Distance (m) Measured PPV (m/s) Theoretical PPV (m/s) 

1 2.89 1.03 0.82 

1 3.86 0.69 0.46 

1 6.98 0.19 0.14 

1 9.75 0.10 0.07 

1 12.19 0.02 0.05 

2 2.28 0.22 0.95 

2 3.35 0.15 0.44 

2 5.73 0.07 0.15 

2 9.21 0.02 0.06 

2 11.8 0.01 0.04 

3 2.19 0.26 1.76 

3 3.14 0.99 0.84 

3 5.81 0.24 0.24 

3 8.57 0.12 0.11 

3 9.30 0.05 0.09 

Table IV- Distance from charge center to accelerometer, measured PPV, and theoretical 

PPV for Zero Test 2. 

For blasthole 1, an examination of the PPV values in Figure 5 reveals the 

measured PPVs are 31% larger than the theoretical PPVs. For blasthole 2, the measured 

PPVs are 55% of the theoretical PPVs. For blasthole 3, the result obtained at the 2.19 m 

distance appears to be an outlier. The four other readings were 23% larger than the 

theoretical PPVs. The larger values of PPV were unexpected for the field results 

compared to theoretically calculated PPVs using the three-dimensional equations for 

blastholes 1 and 3 because the rock mass is quite jointed. Others, however, have reported 

similar results (Arbiev 1964, Zaitsev 1968, Tseitlin & Smolin 1972). The conclusions 

from the Kiruna data are: 

•	 Because PPV's from blasthole 1 were measured in virgin rock and 

blasthole 3 results were only 8% less than those from blasthole 1, 

blasthole 3 had little damage from either blasthole 1 or blasthole 2. Thus, 

based on blasthole spacing shown in Figure 4 for blasthole 1, the damage 

extent was greater than 0.9 m but less than 2.5 m. 

•	 For blasthole 2, which was damaged, the damage range was less than 1.6 

m. 

•	 Because the measured PPVs for blasthole 1 were 31% larger than the 

theoretical PPVs calculated using the theoretical three-dimensional, 

hydrodynamic-based equations, the expected PPVs in Kiruna virgin rock 

can be calculated using the theoretical three-dimensional equations and 

then multiplied by 1.31. 

•	 Equation (12), which is a simplification of the theoretical threedimensional equations, can be modified to calculate expected PPVs in 

Kiruna virgin rock along the x axis as shown in Figure 1 by multiplying 

the results by 1.31. 
A range for the critical PPV for the Kiruna rock mass is then calculated as 

follows. The parameter I is first determined by substituting the density ofthe explosive, 

the specific energy ofthe explosive, and the density of the rock into equation (13). The 

result is 

I = 303 

The theoretical radial velocity is then computed using equation (12) as follows: 

(25) 


Applying the calibration factor for the Kiruna rock mass, equation (15) becomes 

(26) 


The charge geometry for blasthole 1 is then used to calculate the critical PPV 

range because the assessed damage was caused by this charge. Substituting 

L 0.48 m, 

d = 0.1 m, 

r=0.9m, 

into equation (14), one finds that 

Gt = 37. 

In turn, equation (26) yields 10.7 mis for the critical PPV (Ut). Similarly, if a value of2.5 

m for r is substituted into equation (14), Gt is computed as 279 and the critical PPV is 

then equal to 1.4 mis. The critical PPV range is then 1.4 mis < PPVlimit < 10.7 mis. As a 

comparison, the limiting PPV based on the unconfined compressive strength ofthe rock 

mass is 

ppTTVlimit -

- (Jc-

Pre - . 

- 49m/s (27) 

where 

O'c unconfined compressive strength ofthe rock mass, MPa 

pr = specific density ofthe rock mass, kg/m3 

c seismic velocity ofthe rock nlass, mis. 

Equation (26) in expanded form is 

Fs(jr d 

r2 

2 + 4 

Uf = 397 L (28) 

d 

If 4.9 mis is used in equation (28), the expected damage distance, r, is 1.3 m. 
4.3 Measurements conducted during drift driving 

Figure 2- Plan view of Kiruna Mine test arrangement ...

As part of the test series, a total of six drift rounds were blasted in the orebody of 

the Kiruna Mine to collect particle velocity measurements at various distances (Jinnerot 

& Nilsson 1998). Each drift had a cross sectional area of about 42 m2 and the nominal 

advance was 5 m. All holes were 48 mm in diameter. The charge length was 4.6 m. No 

stemming was used. Of the six rounds, only data from rounds 3 and 5 were analyzed 

because drilling precision on the other rounds was low or accelerometers malfunctioned. 

Blasthole locations for these two rounds are provided in Figures 6-9. Accelerometers 

were installed in measurement blastholes that were drilled perpendicular to test Drift 406 

from the adjacent parallel Drift 408 as shown in Figure 2. Kimulux R explosive was 

pumped into the stoping and easer/helper holes and, hence, the explosive was fully 
 

coupled. The contour holes, on the other hand, were charged with 22-mm-diameter, 

Kimulux 42 cartridges which were decoupled. The peak particle velocity measurement, 

distance from the center of each charge to each accelerometer, and calculated PPVs using 

equations 1 through 11 are listed in Tables V and VI for rounds 3 and 5, respectively. 

Figure 6- Blast pattern for drift round 3 

Figure 7- Plan view of blastholes and accelerometers for Drift 3 on approximately the 

same horizon. 
Figure 8- Blast pattern for drift round 5.

Figure 9- Plan view of blastholes and accelerometers for Drift 5 on approximately the 

same horizon.

Blasthole Accelerometer Distancea 

(m) 

Measured 

PPV (m/s) 

Calculatedb 

(m/s) 

3.7 2 3.0 0.959 2.433 

3.7 3 5.46 0.262 0.809 

3.8 3 4.86 0.327 0.791 
 

 

 

 

 

 

 

 

 

2.11 1 3.32 0.438 1.671 

2.11 2 4.68 0.274 0.845 

2.11 3 7.5 0.114 0.351 

2.12 3 7.47 0.113 0.356 

2.12 4 15.92 0.021 0.080 

2.13 3 7.47 0.135 0.350 

2.13 4 16.02 0.025 0.079 

3.1 1 2.5 0.803 2.583 

3.1 2 3.8 0.465 1.221 

3.1 3 6.63 0.182 0.444 

3.1 4 15.09 0.038 0.090 

3.2 3 6.63 0.11 0.444 

3.2 4 15.13 0.021 0.089 

3.4 2 2.8 0.514 2.059 

3.4 3 5.72 0.126 0.589 

3.4 4 14.25 0.022 0.101 

3.5 3 5.7 0.122 0.588 

3.18 1 4.06 0.525 1.164 

3.18 2 5.55 0.306 0.745 

3.18 3 8.24 0.193 0.363 

3.18 4 16.39 0.028 0.087 

3.19 1 3.53 0.519 1.534 

3.19 2 4.89 0.314 0.990 

3.19 3 7.5 0.225 0.453 

3.19 4 15.6 0.038 0.098 

3.20 1 2.67 0.639 2.313 

3.20 2 3.79 0.418 1.415 

3.20 3 6.36 0.222 0.562 

3.20 4 14.5 0.039 0.106 

3.10c 2 1.47 1.168 NA 

3.10 c 3 4.34 0.105 NA 

3.11 c 1 1.81 0.711 NA 

3.11 c 2 1.1 0.501 NA 

3.12 c 2 1.77 0.314 NA 

3.12 c 3 4.39 0.070 NA 

3.13 c 1 2.92 0.101 NA 

3.13 c 2 2.55 0.100 NA a

Distance from center of charge to accelerometer 

b

Calculated using equation 11 

c

Decoupled 

Table V- Measured distance from charge, measured PPV, and calculated PPV for round 

3. 

Blasthole Accelerometer Distancea 

(m) 

Measured 

PPV (m/s) 

Calculatedb 

PPV(m/s) 
 

 

 

 

 

 

 

 

 

 

3.10 2 2.49 0.708 2.444 

3.10 4 13.6 0.025 0.110 

2.18 2 5.04 0.493 0.742 

2.19 2 4.55 0.392 1.077 

2.19 3 7.07 0.167 0.477 

2.19 4 15.09 0.051 0.099 

3.1 1 3.34 0.845 1.749 

3.1 2 4.89 0.524 0.792 

3.1 3 7.58 0.218 0.344 

3.2 2 4.9 0.536 0.825 

3.4 1 2.62 0.478 2.265 

3.4 2 4.26 0.452 1.002 

3.4 3 7.0 0.202 0.402 

3.4 4 15.25 0.045 0.088 

3.5 1 2.53 0.987 2.688 

3.5 2 4.04 0.656 1.100 

3.5 3 6.78 0.259 0.425 

3.5 4 15.11 0.056 0.089 

3.6 1 2.9 1.244 3.219 

3.6 2 4.12 0.802 1.121 

3.6 3 6.71 0.338 0.435 

3.6 4 14.98 0.073 0.091 

3.7 1 2.45 1.570 5.588 

3.7 2 3.47 1.156 1.558 

3.7 3 6.01 0.441 0.535 

3.8 1 2.67 1.334 2.953 

3.8 2 4.21 1.241 1.337 

3.8 3 6.76 0.542 0.596 

3.8 4 14.27 0.112 0.110 

3.12c 1 .87 1.529 NA 

3.12 c 3 4.65 0.232 NA 

3.12 c 4 12.87 0.044 NA 

3.13 c 2 1.26 0.292 NA 

3.13 c 3 4.5 0.073 NA 

3.13 c 4 12.84 0.014 NA 

3.15 c 1 2.1 1.070 NA 

3.15 c 2 3.07 0.390 NA 

3.15 c 3 5.25 0.146 NA 

3.15 c 4 13.11 0.038 NA a

Distance from center of charge to accelerometer 

b

Calculated using equation (11) c

Decoupled 

Table VI- Measured distance from charge, measured PPV, and calculated PPV for round 

5. 
 

 

5. ANALYSIS OF BLAST DAMAGE IN THE DRIFT ROUNDS 

The damage range for a fully coupled charge of Kimulux R in the 48-mm 

diameter holes (stoping and easer/buffer) can be calculated using equation (28). For the 

limiting critical PPV values (PPVmin = 1.4 m/s and PPVmax = 10.7 m/s) obtained in Zero 

Test 2, the corresponding values of Gt are 281.4 and 37.2, respectively. Beginning with 

PPVmin, substituting Gt equals 281.4 together with the required charge dimensions into 

equation (28), _ equals 85.5. 

For a blasthole diameter of 48 mm, the maximum predicted damage radius (r) 

would be 4.1 m. Applying the same procedure for PPVmax equal to 10.7 m/s, the 

predicted damage radius equals 1 m which is considered to be a more reasonable value. 

The damage range for a single fully coupled hole is then 1 m to 4.1 m. 

Theoretical velocities using equations 1 through 11 are compared to measured 

velocities for fully coupled rounds 3 and 5 in Tables V and VI. Some holes are located 

approximately on the same elevation as accelerometers 3 and 4, which are positioned 

close to a line perpendicular to the centroid of each round. These conditions justify the 

application of equation 25 to calculate PPV. A charge length equal to 4.6 m and a 

blasthole diameter equal to 0.048 m are used to calculate Gt for the chosen distances. 

These values are then substituted into equation (26). The results are listed in Table VII 

and plotted in Figure 10. As shown in Tables V through VII and Figure 10, the measured 

PPVs are much less than the calculated PPVs. This indicates that blast damage occurred 

around each charge prior to detonation. This observation is in agreement with that made 

by Blair (Blair & Armstrong 2001). The damage distance is at least equal to the blasthole 

spacing of about 1 m which is compatible with the calculated damage range based on 

PPVmax. If the calculated PPV values from Table VII are reduced by using the regression 

equation for blasthole 3 shown in Figure 5, the calculated PPV's are closer to the 

measured PPVs. The reduced PPV values are plotted in Figure 10. This is another 

indication that the rock around blastholes in rounds 3 and 5 was damaged prior to 

detonation. 

Figure 10- PPV versus Gt for coupled charges, rounds 3 and 5. 
Round Blasthole Accelerometer Distance a 

(m) 

Measured 

PPV (m/s) 

Gt Calculatedb 

PPV (m/s) 

3 2.12 (Et 3 7.5 0.113 864 0.46 

3 2.12 (S)d 4 15.8 0.021 3760 0.11 

3 3.2 (S) 3 6.7 0.11 697 0.57 

3 3.2 (S) 4 15.1 0.021 3387 0.12 

3 3.5 (S) 3 5.7 0.122 514 0.77 

3 3.8 (E) 3 4.9 0.327 389 1.01 

5 3.5 (S) 3 6.8 0.259 717 0.55 

5 3.5 (S) 4 14.9 0.056 3299 0.12 

5 3.10 (E) 4 13.4 0.025 2675 0.15 

aDistance from center of charge to accelerometer 

bCalculated using equation (26) CEaser hole dStoping hole 

Table VII- Measured and calculated PPV for coupled charges, Rounds 3 and 5. 

The expected PPV values from the contour rounds can be calculated by applying 

modifying factors to equation (26). The explosive parameter, I, for Kimulux 42 which 

was used in the contour rounds is i equals 310. Dividing by I equals 303, the explosive 

parameter for Kimulux R used for Zero Test 2, one obtains 

!:.. = 310 = 1.023 

I 303 

The decoupling factor (re/rh) is 0.458. Applying these factors to equation (26) yields 

(29) 
 

Figure 5- Measured versus theoretical PPV for blastholes 1-3.

 

As shown in Table VIII, the measured PPV values from the decoupled holes 

located on the measurement hole horizon are much less than the PPV values as calculated 

from the Zero Test 2 results. This indicates that the charges in the buffer/easer/helper 

holes likely caused damage in the rock mass containing the contour hole. As a result of 

this damage, the particle velocity carried by the p-wave from the contour charge is 

presumed to have been strongly attenuated. This is consistent with observations by 

Jinnerot and Nilsson (1998) who could not confirm visible perimeter damage in 1.5-m by 

1.0-m saw cuts made in the drift walls after excavation. The observations, however, were 

hampered by the presence of the natural jointing and joint variability. They further state 

that the cracks that one sees are probably natural cracks with a variation which is 

geologically based. If the calculated PPV values from Table VIII are reduced by using 

the regression equation for blasthole 2 shown in Figure 5, the calculated PPVs are closer 

to the measured PPVs but still larger. This reflects the severity of damage around the 

decoupled blastholes. The reduced PPVs are listed in Table VIII. 

Round Blasthole Accelerometer Distancea 

(m) 

Measured 

PPV 

(m/s) 

Gt Calculated PPV 

(m/s) 

3 3.11 2 1.8 0.501 77 2.4b 1.31c 

5 3.13 2 2.0 0.292 90 2.1 1.15 

5 3.13 3 4.6 0.073 347 0.54 0.29 

5 3.13 4 12.7 0.014 2407 0.08 0.03 a

Distance from center of charge to accelerometer 

b

Calculated using equation (26) c

Calculated using equation (26) modified for damaged rock 
Table VIII- Measured and calculated PPV for decoupled charges, rounds 3 and 5. 

6. APPROACH TO CONTROLLED BLASTING 

Figure 11- Coinciding damage limits (after Holmberg 1982).

Figure 11 (Holmberg 1982) is a diagrammatic representation of the contour 

control blast design principle behind the Holmberg (1982) approach. One begins with the 

design of the contour row and selects the charge concentration and hole spacing based on 

the allowable damage limit. Knowing the location of the maximum damage limit outside 

of the perimeter, one selects the explosive charge and the easer hole location so that the 

damage limit from the easer row does not exceed that of the contour row. The same 

procedure is followed for the stoping row of holes. The design curves provided by 

Holmberg & Persson (1978, 1979) relating PPV to the distance as a function of the linear 

charge concentration is often applied for this purpose (see Figure 12). This design 

approach assumes that the same set of curves applies for each of the different holes. 

However, it does not take into account the fact that in practical application the charges 

are detonated in the opposite order from that of the design. The stoping holes are blasted 

first, followed by the easer row, and finally the contour row is shot. Depending on the 

charging and proximity of the holes to one another, various degrees of damage are 

induced to the adjacent rock mass before the given explosive detonates. For example, if 

the limiting PPV is 1,000 mm/s, then the damage distance in fresh rock for a charge 

concentration of 1.5 kg/m is about 1.4 m as shown in Figure 12. If the rock is 

predamaged, then the actual contour line would lie below the design curve. For 

illustrative purposes, if this line coincides with the 0.5 kg/m contour line based on virgin 

rock conditions, then the damage for the same charge concentration of 1.5 kg/m is only 

0.7 m. 
 

Figure 12- Peak particle velocity as a function of distance and charge concentration for a 

3-m-long charge (after Holmberg & Persson 1979). 

 

The results reported in this paper show that the predamage can be significant and 

the peak particle velocities are expected to be less, in fact much less, than might be 

predicted using theoretical curves such as given in Figure 12. This suggests that the 

perimeter design approach is conservative. These results also help to explain why the 

extent of damage from fully coupled perimeter holes is often less than might be 

predicted. In this case, some damage to the rock containing the contour holes has 

probably been done by the easer row of holes and a more rapid attenuation of the damage 

producing waves occurs than would normally be the case. 

The effect of pre-damaged rock and associated wave attenuation on damage 

distance is also demonstrated by examining the results of Zero Test 2. Figure 13 is a plot 

of PPV versus scaled distance. The limiting PPV as defined by Equation (27) is equal to 

4.9 m/s for the Kiruna rockmass. The scaled damage distance for blasthole 1, which was 

located in intact rock is 0.8 m/kg0.5 and the scaled damage distance for blasthole 2, which 

was located in damaged rock is 0.3 m/kg0.5 . Using charge geometry from Table 2 and 

charge density from Table 3, the damage distances for blastholes 1 and 2 are 1.7 m and 

0.5 m, respectively. 
Figure 13- Peak particle velocity versus scaled distance for Zero Test 2. 

7. CONCLUSION 

Velocity and distance measurements from a series of single-shot tests performed 

by Swedish researchers at the Kiruna Mine, together with equations based on 

hydrodynamics, were used to develop PPV versus distance data for undamaged rock. 

Based upon knowing the charge distances at which damage was present or absent, it was 

possible to bracket the critical peak particle velocity. In this case, the PPV range was 

quite large ranging from 1.4 m/s to 10.7 m/s. In the future, some special observation 

techniques, such as the visual inspection of rock damage from a saw cut into the rib after 

a single blast, could provide a smaller range for the critical PPV. In this regard, Olsson 

(Olsson et al. 2009) have recently presented 3D fracturing results from a very complete 

set of such saw cuts in granite. 

The equation developed from the single-charge tests was then used to calculate 

the expected PPV values at various known distances from drift round charges with 

different geometry than the charges used in the single-charge test. A comparison between 

calculated and measured PPV values for the stoping, easer, and contour holes indicate 

that, in all cases, there was some apparent predamage to the rock surrounding the charges 

prior to their detonation. The result was that the measured PPV values were significantly 

less than would be predicted based on tests conducted in undamaged rock. 

The findings are highly significant and positive in that designs based on the use of 

PPV versus distance curves obtained in fresh rock will be conservative, perhaps quite 

conservative. The actual damage extent is expected to be less than predicted and 

designed. In this situation, the waves emanating from even a fully coupled perimeter 

charge could be rapidly attenuated if the hole was in the influence zone of the easer hole 
 

row. This could account for the fact that sometimes the overbreak associated with fully 

coupled perimeter charges is less than anticipated. 

This excellent set of data produced by LKAB and SveBeFo has offered an 

opportunity to apply an analysis technique based on hydrodynamics and to gain an 

insight into the complicated blast damage process. The data have been included so that 

others might apply their own analysis techniques. In particular, the effect of end 

initiation as opposed to instantaneous detonation, which is assumed in the Neiman 

approach, could be addressed. 

ACKNOWLEDGEMENT 

The authors wish to thank Sten Fernerud, Fenerud Engineering AB, Umea, 

Sweden, and Anders Nordqvist, LKAB, Kiruna, Sweden, for providing information on 

Zero Test 2. 

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