Environ Earth Sci DOI 10.1007/s12665-015-4319-5
ORIGINAL ARTICLE
Human comfort evaluation criteria for blast planning Shihai Chen1,2 • Zihua Zhang1 • Jian Wu1
Received: 15 May 2014 / Accepted: 19 March 2015 Springer-Verlag Berlin Heidelberg 2015
Abstract To date, blasting vibration safety control standards have focused on minimizing structural damage to the surrounding buildings, and the effects of blasting vibration on people living and working around the blasting site have been overlooked. Blasting vibrations can cause great discomfort and result in lawsuits for compensation. In this paper, the level of discomfort for humans under different blasting vibration levels is classified and investigated. These human responses are quantified by traditional mechanical vibration comfort indicators, such as the vibration dose value and the integrated weighted acceleration. A wavelet transform method is used to analyze the vibration velocity signals and obtain the blasting vibration energy. The evaluation criteria for assessing blasting vibration comfort are presented in a case study. The results have important significance in ensuring blasting safety and maintaining social stability. Keywords Blasting vibration Vibration comfort Evaluation criterion Energy
Introduction In recent years, engineering rock blasting has been widely and effectively used in urban subway construction, mining engineering, hydropower engineering, comprehensive development of underground space, and other major & Shihai Chen
[email protected] 1
Huaqiao University, Xiamen 361021, China
2
Shandong University of Science and Technology, Qingdao, China
infrastructure constructions. While blasting environments become more complex and the awareness of safety and environmental protection around the work site improves, the number of civil disputes and complaints regarding the negative effects of blasting is increasing. In particular, the effects of blasting vibration have raised many concerns and even resulted in lawsuits for compensation. Therefore, controlling the impact of blasting vibration on people living and working around blasting sites has become an important issue (Kuzu and Guclu 2009; Li and Deng 2012) and can help engineers reduce the negative impact of blasting and maintain social stability. Blasting vibration comfort is a measure of the degree of discomfort humans experience from blasting vibrations in the natural state. Evaluation criteria and blasting vibration methods taking humans into consideration have been proposed (ISO 2007; BS 2008; Griffin 1990; GB 1989). However, most of these criteria were developed to assess automobile vibrations by considering mechanical vibrations based on simple harmonic vibrations over a short period. To date, there are no exact evaluation criteria for transient impact vibrations. Song et al. (2010) introduced a method for evaluating blasting vibration comfort and based their evaluation criteria on mechanical vibrations. The US Bureau of Mines surveyed and analyzed the effects of blasting vibration on humans and discovered complaint rates of 5 % when the peak vibration velocity was 5 mm/s and 10 % when the peak vibration velocity was 10 mm/s. Raina et al. (2004) investigated four metal mines in India and documented the human response at different distances from the blasting source. Griffin (1990) proposed the vibration dose value (VDV) and investigated the level of discomfort in individuals when their whole body was subjected to shock vibration from a ‘‘shock machine’’. The German standard DIN4150-2 uses the maximum weighted
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Environ Earth Sci
vibration intensity to evaluate the effects of blasting vibration on humans. Currently, with development and construction increasing globally, to reduce the number of civil disputes and litigations caused by blasting work, new methods to evaluate blasting vibration comfort in residential areas are needed.
Mechanical vibration comfort evaluation method Current vibration comfort criteria for humans are mostly based on mechanical vibrations. The weighted vibration acceleration function is obtained in the corresponding physiological coordinates based on the measured vibration acceleration signal via a target filter. Then, through the weighted function, the suitable dosage can be derived.
For different filters, the filter coefficients ak and bj are different (Table 1). Evaluation criteria Currently, three indicators are used to evaluate the human body’s response to vibration: the root-mean-square (rms) weight of acceleration (ms-2), the vibration dose VDV (ms-1.75), and the estimated vibration dose eVDV (ms-1.75). The three indicators are calculated as follows: sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 0 !1=2 1 Z Ns X 1 T 2 1 A a ðtÞdt @or awrms ¼ a2 awrms ¼ T 0 w Ns i¼1 wi ð2Þ 1 ! 1=4 Z T 1=4 Ns X @or VDV ¼ Ts A ½aw ðtÞ4 dt a4i VDV ¼ N s 0 i¼1 0
Weighted vibration acceleration function
ð3Þ
The vibration comfort evaluation at different positions is based on the measured frequency of the vibration signal weighted by a triple filter (Hh, Hl, Ht) (Rimell and Mansfield 2007; Chen et al. 2011). For the measured signal-weighted method, a time-domain digital filter (an infinite impulse response filter) based on the following formulation (Yan et al. 2012) is used: " # M N X 1 X aw ðtn Þ ¼ bj aðtnj Þ ak aðtnk Þ ð1Þ a0 j¼0 k¼0 where a(t) is the measured signal, aw(t) is the vibration signal after frequency weighting, ak and bj are filter coefficients, M is the number of zeros in the transfer function of the filter system, and N is the pole number of the transfer function of the filter system. Here, both M and N are equal to 2, and n is the discrete point number of the signal.
Table 1 Filter coefficients
Filter coefficients
a0 a1 a2 b0 b1 b2
eVDV ¼ ½Ts ð1:4awrms Þ4 1=4
ð4Þ
where awrms is the estimated vibration dose, aw(t) is the weighted time history function of the measured vibration acceleration signal, T is the duration of the vibration, and Ns is the discrete sample points. Blasting vibrations occur in three-dimensional space. Therefore, when evaluating the vibration comfort, the effects of the indicators in three directions (X, Y, and Z) should be considered. The conversion method (unified converted to Z-axis) is as follows: aw ¼ ½ð1:4awrmsx Þ2 þ ð1:4awrmsy Þ2 þ a2wrmsz 1=2
ð5Þ
VDV ¼ ½ð1:4VDVx Þ4 þ ð1:4VDVy Þ4 þ ðVDVz Þ4 1=4
ð6Þ
eVDV ¼ ½ð1:4eVDVx Þ4 þ ð1:4eVDVy Þ4 þ ðeVDVz Þ4 1=4 ð7Þ
Triple filter Hh
Hl
pffiffiffi 2 2 þ 4A þ 4A2 pffiffiffi 8A2 4 2 pffiffiffi 2 2 4A þ 4A2 pffiffiffi 2 2 pffiffiffi 4 2 pffiffiffi 2 2
pffiffiffi pffiffiffi 2 2 þ 4B þ 2 2B2 pffiffiffi 2 pffiffiffi 4 2B 4 2 pffiffiffi pffiffiffi 2 2 4B þ 2 2B2 pffiffiffi 2 2 2B pffiffiffi 4 2B2 pffiffiffi 2 2B2
Ht 2 ? 4C ? 2C2 4C2 - 4 2 - 4C ? 2C2 2C2/D ? 2C2 4C2 2C2 - 2C2/D
Note that A, B, C, and D in Table 1 represent the filtering parameters of the frequency filter, which can be generally represented as /i = tan (fcp/fs). Here, /i represents the parameters A, B, C, and D. fc is the central frequency of each filter. The values of fcA, fcB, fcC, and fcD are 0.7943, 100, 5.684, and 5.68, respectively. fs is the sampling frequency where s = j2pf
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Environ Earth Sci Table 2 Survey data used for vibration comfort evaluation Sequence number
Date
1
Apr 2
Respondent information
Sequence number
Date
Apr 7
Score
Gender
Age
Identity
Distance from blasting area (m)
4
Male
25
A
35
27
3.5
Male
25
A
35
28
3
5
Male
70
B
35
4
4
Male
75
B
5
6
Male
75
B
6
7
Female
75
B
7
6
Male
80
B
35
33
8
6
Female
65
C
30
34
2
9 10 11
Apr 4
Respondent information Score
Gender
Age
Identity
Distance from blasting area (m)
3
Male
30
A
30
3
Male
40
D
30
29
4
Male
35
E
30
35
30
3
Male
40
E
25
35
31
5
Male
40
C
30
35
32
3
Male
25
A
30
2
Male
25
A
30
5
Male
30
F
30
Apr 12
5
Male
40
D
30
35
6
Male
40
D
30
2
Male
25
A
35
36
6
Male
55
J
30
2
Male
25
A
35
37
6
Male
40
E
25
12
3
Male
40
E
15
38
6
Male
25
A
30
13
4
Male
35
E
15
39
7
Male
35
C
30
2 5
Male Male
25 25
F A
35 25
40 41
7 8
Female Female
35 30
C H
30 30
14 15 16
Apr 6
Mar 31
6
Male
25
A
25
42
17
8
Female
45
B
30
43
18
6
Male
35
E
15
44
8
Female
55
H
30
19
7
Female
25
F
15
45
9
Female
35
H
30
Apr 8
8
Male
45
B
30
46
8
Female
55
K
30
7
Female
25
F
15
47
7
Female
60
H
30
Apr 9
7
Male
25
A
35
48
9
Female
65
H
30
20 21 22 23
8
Female
30
H
30
7
Female
35
H
30
7
Male
25
A
35
49
9
Female
60
H
30
24
8
Male
25
F
35
50
9
Female
35
H
30
25
8
Female
70
B
35
51
8
Female
30
H
30
26
8
Female
75
B
35
52
8
Female
45
H
30
The identity code of the respondents: A–L represents blasting-monitoring staff, local residents, passersby, site supervisions, drilling and blasting workers, site construction technicians, students, parents, teachers, security staff, soldiers, and kindergarten guards, respectively
Here, awrmsx, awrmsy, and awrmsz are the weighted rms accelerations, VDVx, VDVy, and VDVz are the vibration doses, and eVDVx, eVDVy, and eVDVz are the estimated vibration doses along the three axes (X-axis, Y-axis, and Zaxis). aw is the converted total weighted rms acceleration; VDV is the converted total vibration dose; and eVDV is the converted total estimated vibration dose.
Energy assessment for blasting vibration comfort criteria The level of discomfort that humans experience from blasting vibrations is directly related to the vibration energy released from rock blasting. The vibration amplitude, frequency, duration of vibrations, and human dynamic response characteristics are important factors. The energy
from blasting vibrations is analyzed by applying wavelet transform to the vibration velocity signal. By decomposing a wavelet packet of -i layers for a given signal x(t), j = 2i sub-frequency bands can be obtained. If the lowest frequency component of the original signal is 0, the highest frequency component is xm; the width of each sub-band frequency is xm/2i. The signal in each frequency band can be extracted by reconstruction of the wavelet packet decomposition coefficients, and the total signal can be expressed as X xðtÞ ¼ xi;k ¼ xi;0 þ xi;1 þ . . . þ xi;j1 ð8Þ k
where xi,k represents the reconstructed signal in the -ith layer decomposition node (i, k), k = 0, 1, 2…, j-1. If a quadratic energy time–frequency spectrum can represent a reconstructed signal corresponding to each
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Environ Earth Sci Table 3 Vibration comfort evaluation criteria
Fig. 1 Vibration comfort evaluation based on the VDV dose
frequency band, then the time–frequency spectrum w(t, xk) can be defined as follows: 2 wðt; xk Þ ¼ xi;k ðtÞ ð9Þ where xk is the central frequency of the k-th frequency band, and its total energy is Z Z 2 Ek ¼ wðt; xk Þdt ¼ xi;k ðtÞ dt ð10Þ where Ek is the reconstructed signal energy, k = 0, 1, 2…, j-1. When the frequency band is sampled at high resolution, it can be approximated as a continuous frequency distribution; the collection {Ek} of the original signal within the frequency range is the power spectral density distribution of the signal.
Comfort investigation and evaluation criteria Survey data A blasting vibration comfort survey was taken for a period of 2 weeks in 2012 at the Qingdao Metro Line 3 construction project in Qingdao, Shandong, China. The survey data are presented in Table 2. We collected data from males and females in the age range 25–75. Vibration comfort criteria To obtain quantitative blasting vibration comfort evaluation criteria, we conducted a survey and documented the respondents’ responses to blasting vibration at different energy levels. To classify and quantify the responses, we
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Comfort level Evaluation index
No feeling
Slight discomfort at acceptable level
Discomfort, likely to complain
Strong discomfort, most likely to complain
aw (m/s2)
B0.01
0.01–0.02
0.02–0.04
C0.04
VDV (m/ s1.75)
B0.2
0.2–0.3
0.3–0.8
C0.8
E (m2/s2)
B0.25
0.25–1.25
1.25–3.75
C3.75
asked the respondents to grade their level of comfort/discomfort according to the following scale. Level 0 indicates no response; 2.5 represents slight discomfort at an acceptable level; 5 means discomfort likely to lead to a complaint; 7.5 indicates strong discomfort that would most likely lead to a complaint; 10 means the respondent feels extreme fear and will definitely complain. The survey results (Table 2) and Eqs. (5), (6), and (10) were used to obtain the evaluation indexes of blasting vibration comfort. The VDV distribution is shown in Fig. 1. The comfort evaluation criteria of blasting vibration are shown in Table 3.
Criteria evaluation using a case study The largest LPG underground storage cavern in Northern China came into operation on May 20, 2009, with a total investment of nearly 90 million dollars and a total capacity of 500,000 cubic meters. The underground blasting operation resulted in some complaints from the local residents; the complaints were because of the physical and emotional effects of the blasting vibration rather than safety issues. The three-direction vibration data at the site (vertical direction: CH1, horizontal radial: CH2, and horizontal tangential: CH3) were collected using IDTS-3850 vibration-monitoring recorders at a sampling frequency of 2 kHz (Fig. 2). The velocity sensors were arranged at the first floor of the residential building. Early test results showed that the integrated weighted accelerations in the three directions were more than 0.04 m/s2, and the integrated vibration doses were in the range of 0.8–1.6. The resulting blasting vibration felt by people at different locations exceeds the vibration comfort limit according to our criteria. Therefore, we can anticipate that such blasting will result in complaints from residents. This was indeed the case, and after receiving the complaints, the deep-hole blasting was replaced by medium-deep-hole blasting, thus reducing the blasting vibrations to a level within the comfort evaluation dose. The complaints of residents ceased, and the smooth progress of the project was ensured.
Environ Earth Sci
0.4
v/cm/s
v/cm/s
0.2 0.0 -0.2 -0.4 -0.6 0.0
0.2
0.4
0.6
0.8
1.0
0.8
1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 0.0
0.6 0.4 0.2
v/cm/s
0.6
0.0 -0.2 -0.4 -0.6
0.2
t/s CH1
0.4
0.6
t/s CH3
0.8
1.0
-0.8 0.0
0.2
0.4
0.6
0.8
1.0
t/s CH2
Fig. 2 Time history curve of blasting vibration. Typical vibration waveforms of vertical direction (CH1), horizontal radial direction (CH2), and horizontal tangential direction (CH3)
Conclusions and discussions To reduce the negative effects on humans caused by blasting work, new comfort evaluations for blasting vibration in residential areas are needed. We present a new blasting vibration comfort evaluation method and standards in combination with mechanical vibration-related vibration comfort standards. The vibration energy released from rock blasting at the Qingdao Metro Line 3 construction project was used to determine the blasting vibration comfort evaluation criteria. We then evaluated our model based on data from the blasting project of Qingdao LPG underground storage cavern. The results show that the strongest vibration intensity that meets the blasting vibration comfort standards is below the safety limit of structural damage. Thus, although a minor blasting vibration is not powerful enough to damage residential buildings, it may cause strong discomfort to nearby residents. Therefore, in blast planning, it is important to consider human vibration comfort.
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Chen SH, Wei HX, Du RQ (2011) Blasting vibration effect analysis of building structures. Coal Industry Press, Beijing China (in Chinese) GB 10070 (1989) Urban Environmental Vibration Standard. China Standard (in Chinese) Griffin MJ (1990) Handbook of human vibration. Academic press, London ISO10137 (2007) Bases for design of structures-Serviceability of buildings and walkways against vibrations. International Standard Kuzu C, Guclu E (2009) The problem of human response to blast induced vibrations in tunnel construction and mitigation of vibration effects using cautious blasting in half-face blasting rounds. Tunn Undergr Sp Technol 24(1):53–61 Li DD, Deng ZD (2012) Evaluation of the effects of blasting vibration on humans in the excavation of CMICT dock. Eng Blasting 12(2):82–85 (in Chinese) Raina AK, Haldar A, Chakraborty AK, Choudhury PB, Ramulu M, Bandyopadhyay C (2004) Human response to blast-induced vibration and air-overpressure: an Indian scenario. Bull Eng Geol Environ 63(3):209–214 Rimell AN, Mansfield NJ (2007) Design of digital filters for frequency weightings required for risk assessments of workers exposed to vibration. Ind Health 45(4):512–519 Song ZG, Bai Y, Jin WL (2010) Vibration serviceability analysis of buildings near the area of blasting operation. J Vib Shock 29(9):129–133 (in Chinese) Yan YF, Chen SH, Zhang QH (2012) Evaluation method and application of blasting vibration comfortableness. Eng Blasting 18(1):78–81 (in Chinese)
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