Proceedings of ERE 2016 
17 
 
Critical Evaluation of Blast- Induced Structural Damage 
Criteria for Buildings around Metal Quarries at 
Thudugala, Kaluthara 
Hettiarachchi MM, Priyasanka IDP, Herath HMWD, Mohanaruban G, 
*Dharmaratne PGR and Hemalal PVA  
Department of Earth Resources Engineering, University of Moratuwa 
*Corresponding author - dharme27@yahoo.com 
Abstract: Quarrying can generate a number of on-site and off-site environmental 
effects as a result of blasting, excavation, crushing, screening, stockpiling and 
transport activities. Blasting is necessary for recovery of ore and production of 
aggregates in most underground and open cut mines, as well as in quarries. 
However, blasting can cause noise and ground vibration, which can have an impact 
upon nearby structures and people living close by. Hence, proper control of blasting 
practices is necessary to ensure both the safety of employees and the protection of 
the community from adverse effects. In Thudugala, in Kaluthura district, people 
those who are living close to quarries are highly subjected to these effects due to 
quarry blasting. In these circumstances, it was decided to conduct a research into the 
ground vibration impact in the area. Due to complexity of structures ranging from 
wattle-and-daub structures which do not have proper foundations to those built 
with good foundations, the applicability of single criteria of 5 mm/sec PPV level of 
vibration which is currently being used in Sri Lanka is inadequate. It is also noted 
that the above vibration criteria has been adopted in Sri Lanka without a proper 
theoretical foundation. In this research program, the propagation of cracks due to 
the blasting was assessed at the initial stage of the project. At the final stage, the 
optimum PPV values will have to be found for different types of structures by 
constructing them. In this area soil overburden is less. Therefore most of the 
structures have been constructed on rock. When blasting takes place, rock tends to 
vibrate and the intensity perceived is very high. Therefore crack propagation is high 
in these particular structures. It is also noticed that the cracks have further 
developed between the period between pre-blast crack survey and post-blast crack 
survey. It is due to large number of un-monitored blasts that have been conducted 
during that period. Therefore to solve this problem, it is recommended to carry out 
continuous monitoring of blasts. 
Keywords: Peak Particle Velocity (PPV), Ground Vibration (GV), Air Blast Over 
Pressure (ABOP), Crack Survey  
1.  Introduction 
Blasting is carried out to fragment 
intact rock enabling the earth moving 
equipment to excavate and haul the 
raw material at a minimum cost [1]. 
Blasting is still considered as the most 
economically viable large-scale rock 
breakage technique, which is 
inevitably utilized by mining and 
construction industries. Blasting 
dissipates a large amount of energy to 
the environment as well as to the 
ground [2].  
Blast-induced damage in rock is a 
significant yet poorly understood area 
in the rock excavation industries. The 
prediction and control of blast 
damage has been traditionally done 
by approximate methods mostly 
Proceedings of ERE 2016 
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based on experience rather than on 
understanding of the physical 
phenomenon. Perhaps the difficulties 
of experimentation and modelling in 
blasting, added to the significant 
imperfections of natural rock masses 
at every scale, the limited knowledge 
on material behaviour at very large 
stresses and loading rates have 
significantly limited the research in 
this area and therefore its 
understanding has been poor [3 and 
4]. This study intends to fill this 
knowledge gap by providing a 
method to be applied to predict and 
control blast-induced damage in rock 
[5]. 
Thudugala area in Kalutara district  
was selected for this project due to the 
concentration of number of quarries 
and many complaints received from 
the people in the area regarding blast-
induced structural damages. Other 
than that, the threshold PPV value 
which is used in Sri Lanka is not 
appropriate for Sri Lankan civil 
structures as they vary from poorly 
built wattle-and-daub structures to 
well-built civil structures. Therefore, 
the main task is to find the optimum 
PPV threshold values for Sri Lankan 
structures, giving due regard to 
constructional aspects. 
2.  Methodology 
2.1.  Awareness programs and 
discussions with relevant 
stakeholders   
A discussion was held to obtain the 
views of the Divisional Secretary, 
Grama Niladari, representatives of 
the quarries and area representatives 
regarding the problem at hand. The 
views of both government officers 
and quarry owners regarding blast 
induced damages could be 
understood from these discussions. 
Areas with most of the damages 
incurred to civil structures could be 
identified through this discussion. 
Figure 1: Location of houses within 200 m radius around the quarries 
 
Proceedings of ERE 2016 
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2.2.  Identification of the 
structures which are mostly 
affected by the quarry-blasting  
Initially, locations of the quarries and 
the mostly affected area from 
quarrying activities are to be 
identified. Then the civil structures in 
the area are to be categorized 
according to their foundation 
conditions and the distance from the 
relevant quarries. 
2.3.  Ground Vibration (GV) and 
Air Blast Over Pressure (ABOP) 
measurements at the nearest 
structures of quarries  
Test blasts were carried out at ICC 
and CML-MTD quarries in 
Thudugala area and the GV and 
ABOP were measured. These 
readings were taken by means of a 
number of blast vibration monitors of 
“Blastmate III” series. 
Table 1: The summary of measured 
blasts 
2.4.  Conducting crack surveys 
Crack surveys were conducted to 
identify the extent of cracks and 
damages in identified structures. In 
relation to CML-MTD and ICC 
quarries, nine houses were found 
within the 200 m radius and in 
relation to the RR and SUNBEEN 
quarries, another nine houses were 
found within the 200 m radius. For 
convenience of the survey, cracks 
were classified. 
To evaluate blast induced damage 
criteria for buildings, two types of 
crack surveys were conducted namely 
pre- crack survey and post-crack 
survey. Post-crack survey was carried 
out after three months lapse of pre-
crack survey to assess the 
propagation of the noted cracks. 
Table 2: Classification of blast-
induced cracks 
Crack width 
W(mm) 
Classification 
W < 1 Minor  
1 < W < 3 Medium  
W > 3 Major  
3.  Results and Discussion 
3.1.  Summary of the discussion 
with   quarry stakeholders 
 Exchange of views and creating 
awareness among the stakeholders 
about this study was made during the 
discussion. A presentation was made 
to the audience by the study team 
regarding blasting and blast-induced-
damage to the civil structures. Finally, 
the future strategic action was 
planned and a tentative time table 
was set for the project. 
 
3.2.  Results of measured GV and 
ABOP of test blasts 
Table 3: Results of test blasts 
Blast Monitoring Results 
11/13/2015 
Blast locations Monitoring points 
B
la
st
 N
o
 
G
P
S
  
C
o
o
rd
in
at
es
 
T
im
e 
Location 1 
(511m) 
Location 2 
(341m) 
G
V
 
 (
m
m
/
s)
 
A
B
O
P
 
 (
d
B
) 
G
V
  
(m
m
/
s)
 
A
B
O
P
  
(d
B
) 
CM
L #1 
151290N 
121151E 
02:1
3 
pm 
0.095 110.9 1.310 106.0 
 
 
 
Quarry Number of blasts 
ICC 150 
CML- MTD 145 
RR 95 
Sunbeen 142 
Total 532 
Proceedings of ERE 2016 
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03/16/2016 
Blast locations Monitoring points 
B
la
st
 N
o
 
G
P
S
  
C
o
o
rd
in
at
es
 
T
im
e 
Location 1  
(H-60) 
Location 2 
 (H-63) 
G
V
 
 (
m
m
/
s)
 
A
B
O
P
 
 (
d
B
) 
G
V
 
(m
m
/
s)
 
A
B
O
P
 
 (
d
B
) 
CM
L #1 
6.55957N 
80.06029
E 
11:4
8 am 
0.25 101.9 0.12 104.1 
03/16/2016 
Blast locations Monitoring points 
B
la
st
 N
o
 
G
P
S
  
C
o
o
rd
in
at
es
 
T
im
e 
Location 1 
 (H-60) 
Location 2  
(H-63) 
G
V
  
(m
m
/
s)
 
A
B
O
P
  
(d
B
) 
G
V
  
(m
m
/
s)
 
A
B
O
P
  
(d
B
) 
CM
L #2 
6.55957N 
80.06029
E 
12:0
4 
pm 
0.25 104.9 0.13 107.0 
CM
L #3 
6.55957N 
80.06029
E 
12:1
2 
pm 
0.25 107.0 0.13 110.6 
ICC 
#1 
6.56305N 
80.06219
E 
12:4
9 
pm 
0.25 101.9 0.11 101.9 
Table 4: Number of blasts within time 
duration (04/01/2016-24/03/2016) 
Number of days spent for 
taking readings 
84 
Total number of Blasts 532 
3.3.  Results of the post-crack 
survey 
Table 5: The summary of propagation 
of cracks in structures 
According to the results, when the 
major cracks are considered, their 
lengths have increased by 2.8% for 
the period of 84 days, but widths 
have not increased during this period. 
This has been the least compared to 
other crack types. 
Medium crack lengths have increased 
by 33.99%. It is a considerable value 
compared to other propagation 
values. Crack widths also have 
increased by 8.93%. Minor crack 
propagation is negligible. 
When a crack develops into a major 
crack, its propagation rate is low. 
However, in medium and minor 
cracks, propagation rate is very high. 
Firstly, a small crack forms as a minor 
crack. Then it develops into a 
medium crack and finally to a major 
crack [6]. 
Some cracks could not be identified, 
because of the modification of the 
structures. Propagation rates of cracks 
per blast for 20 holes are summarized 
in Table 6. 
Table 6: Propagation rate per blast 
Cracks 
% Propagation rate 
Length Width 
Major 0.005 0.000 
Medium 0.064 0.017 
Minor 0.017 - 
4. Conclusions and               
Recommendations 
4.1.  Conclusions 
In Thudugala area, cracks are 
propagated throughout the period. 
According to the results of this study, 
cracks propagated as shown below: 
 Propagation of major crack length 
per blast = 0.53% 
 Propagation of major crack width 
per blast = 0.00% 
 Propagation of medium crack 
length per blast = 6.39% 
 Propagation of medium crack 
width per blast = 1.68% 
 Propagation of minor crack length 
per blast = 1.68%  
As per the results, propagation rate of 
the cracks are in the following order: 
Major Crack < Minor Crack < 
Medium Crack  
Cracks 
type 
% Propagation rate 
Length Width 
Major 2.80 0.00 
Medium 33.99 8.93 
Minor 8.96 - 
Proceedings of ERE 2016 
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During the time period, new cracks 
have formed in addition to the 
previous cracks. House No.H–04 is a 
special case because it has been 
constructed on the rock. Therefore the 
ground vibration intensity of that 
place is quite large compared to other 
places. Hence there were many cracks 
appeared in that house. 
According to the data obtained 
during blast monitoring, PPV value 
and Air Blast Over Pressure have not 
exceeded the values specified in the 
Central Environmental Authority 
(CEA) guide lines. There have been 
no complaints during the project 
period of monitored blasts. However, 
people informed the project team that 
they felt very high vibrations and 
were strongly critical of the effects 
during the unmonitored blasting 
period. 
In this area soil overburden is less. 
Therefore most of the structures have 
been constructed on rock. When 
blasting takes place, rock tends to 
vibrate and the intensity perceived 
was very high. Therefore crack 
propagation is high in these 
particular structures. It is also noticed 
that the cracks have further 
developed between the period of pre-
blast crack survey and post-blast 
crack survey. It is due to large 
number of un-monitored blasts that 
have been conducted during that 
period.  
4.2.  Recommendations 
To solve the problem of noise and 
ground vibration, it is recommended 
to carry out continuous monitoring of 
blasts. This project needs to be 
continued in the future by 
constructing houses with different 
foundations and building materials as 
planned, as the effect of blasting may 
be different on differently built 
structures. 
Acknowledgements 
Our gratitude goes to all academic 
and non-academic staff of the 
Department of Earth Resources 
Engineering of University of 
Moratuwa, the management of CML-
MTD Construction (Pvt) Ltd for 
extending the facilities of the 
Thudugala Quarry (Neboda, 
Kalutara), Metal Mix (Pvt) Ltd, ICC 
(Pvt) Ltd and  RR Construction (Pvt) 
Ltd for facilitating us in conducting 
field tests and the companies helped 
us to conduct field tests during this 
study. 
GramaNiladhari –Thudugala, 
Regional Mining Engineer of the 
Kalutara District, Chief Mining 
Engineer at Gelogical Survey & Mines 
Bureau (GSMB) and Divisional 
Secretariat of Dodangoda area are 
also acknowledged for their prompt 
assistance in procuring the explosives 
and accessories for the Project and 
granting approvals giving due 
recognition for this research work. 
References 
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Explosives a rock blasting, Atlas 
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Hashemolhosseini, H. (2013) 
Development of a fuzzy model for 
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Proceedings of ERE 2016 
22 
 
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