An investigation into the environmental effect of blast induced vibrations in the limestone and schist quarries nearby the water supply reservoir of Catlca-Istanbul, Turkey

Category Mine
Group GSI.IR
Location 20th WORLD MINING CONGRESS 2005
Author Cengiz Kuzu `Erkin Nasuf Turker Hudaverdi*
Holding Date 14 January 2006
 
ABSTRACT
 
Limestone quarries, which play an important role in supplying raw materials for the construction industry, usually operate within the city limits. The environmental problems faced in these quarries more frequently are in the form of blasting vibration effect on the surroundings and also on the rock formations. The quarries investigated in this paper are situated nearby one of the water supply reservoir of Istanbul City. The blasting induced vibrations are measured within the two adjacent limestone and schist quarries and the results so obtained are evaluated according to the frequency and particle velocity parameters which are actually prescribed in worldwide well-known 4th OSMRE Procedure (US Department of Interior Office of Surface Mining Reclamation Enforcement). According to results a new blast design is used to improve blast efficiency and to reduce blast induced vibrations. Apart from this, empirical relations including geological characteristics and technological parameters of blasting is derived for predetermination of peak particle velocity (PPV) for each quarries which is also prescribed in OSMRE Procedures (3rd Procedure).
Key words: Vibration monitoring, blast vibrations, blasting and environmental effects.
 

 

INTRODUCTION
 
In recent years, blast induced vibrations come out as an important environmental effect from mining operations. This environmental effect creates more problems especially in aggregate mining. Usually aggregate mines (quarries) are operated near to the cities in order to reduce transportation costs. In developing cities like Istanbul, the quarries out of the city approach the residential areas gradually, because of the rapid growth of the cities. Naturally, blast induced vibrations cause significant problems between quarries and the residents near the quarries. As seen in Table 1, the most important parameters for a controlled blasting are the limitation of the explosive charge per delay and the parameters serving to produce new free faces in breaking process.
 
A blast creates ground waves similar to ripples on a pond when a stone is thrown in, with individual points on the surface moving up and down as the wave passes through. The vibrations are basically sinusoidal with parameter displacement, wavelength, frequency, acceleration and particle velocity. The magnitude of the vibrations increase with the amount of the explosive fired per delay, and decreases with distance. PPV is the main element to examine the vibrations almost in all new investigation procedures for blast induced vibrations (Brook and et al., 1988; Siskind, 2000).
 
METHODS AND RESULTS
 
Every hard rock quarrying operation extracts stone from its geologic formation by the controlled use of explosives. No aspect of quarrying causes more apprehension or is less understood than blasting. Lay perceptions of blasting are often based on movie or television scenes showing dust and debris flying in all directions accompanied by thunderous noise. These spectacular productions reinforce the idea that the use of explosives is an ultra hazardous activity. They do not represent, what actually happens in modern, well-controlled blasting operations (Barksdale, 1996).
 
Quarries under consideration in this study are situated on a hill nearby water supply reservoir (Figure 1). There are residence and industrial buildings around the quarries. It is the aim of this investigation to measure and control by good blasting practise the level of blast induced vibrations so that they stay within safety limits. In practice, the regulations and the design/monitoring procedures needed for complying with the regulations go together and they will be discussed that way in this section. It is therefore firstly an introduction about the procedures of OSMRE will be made and secondly results will be discussed obtained by electric and non-electric initiation systems (Rosenthal and Marlock, 1987; Hustrulid, 1999).
Figure 1: The city of Istanbul and location of the quarries
 
Degree of Importance
V
I
L
 Controllable factors
 1
Charge weight per delay
X
 
 
 2
Length of delay
X
 
 
 3
Detonator accuracy
X
 
 
 4
Burden and spacing
 
X
 
 5
Stemming type and length
 
 
X
 6
Charge length and diameter
 
 
X
 7
Inclination of holes
 
 
X
 8
Direction of initiation
 
X
 
 9
Charge weight per blast
 
 
X
 10
Charge dept
 
 
X
 11
Usage of detonating cord
 
X
 
 12
Initiation system
 
X
 
 Uncontrollable factors:
 1
Topography
 
X
 
 2
Specifications of overburden
 
X
 
 3
Atmospheric conditions
 
 
X
V: very important // I: important // L: less important
 
Table 1: Controllable and uncontrollable factors affect vibration levels
 
PROCEDURES OF OSMRE
 
Over the years a number of criteria relating ground motion to structural damage has been established and implemented with varying degrees of success. One of them based on peak particle velocity has been developed as a regulation by OSMRE. These are presented in the following chapters and also discussed by means of a case study of above-mentioned limestone and schist quarries. In all procedures of OSMRE the PPV plays important role. These procedures are; limiting particle velocity, scaled distance equation, modified scaled distance and blasting level chart (Anonymous, 2005).
 
Limiting particle velocity criterion: In this procedure, (30CFR Section 816.67(d)(2)(i); CFR is for Code of Federal Regulations from USA) the vibration values of each shot are recorded. Each of the three components of the particle velocity is analysed according to limit values mentioned in Table 2. If three components of the particle velocity are under the limit value, the blast is defined as harmless for environment. In this procedure, there is no need to know frequency.
 
Distance
Maximum PPV
0-300 feet
1.25 in./sec.
301-5000 feet
1.00 in./sec.
³5001 feet
0.75 in./sec.
 
Table 2: PPV limits as a function of distance
 from blasting site
 
Scaled distance (SD) equation criterion: In this procedure (30CFR Section 816.67(d)(3)(i)), maximum charge amount (W) is determined per a minimum delay time of 8msec by SD-factor (Siskind, 2000). SD-values are general values and very conservative. Sometimes, this approach may limit explosive usage too much and this method does not require that blasts be monitored. This SD-factor is related to the slop-distance between shot and measurement stations (D) to fix maximum charge (Anonymous, 2005). Table 3 presents the maximum amount of explosives, which can be shooting per 8 msec or greater delay as a function of distance and SD-factor. The equation used to determine the SD is represented below;
SD= D W-0.5                                                            (1)
 
Modified scaled distance criterion: As it is explained in scaled distance equation criterion, it is most restrictive and the only non-site specific criterion. On the other hand, “modified scaled distance criterion” and following “blast level chart criterion” is more effective under more critical conditions (30CFR Section 816.67(d)(3) (i)&(ii)). In this procedure, a statistical approach eliminates the need for regular monitoring of every shot and allows to the blaster to produce a site-specific scaled distance factor. By doing so, this new site-specific scaled distance factor gives to the blaster a chance to predict the PPV depending on geological and technological site factors (H, ک) using the so-called attenuation formulae;
PPV= H (SD)-b                                                       (2)
 
It should be noted that for a valid statistical analysis >30 data pairs (PPV-SD) are required. Once a modified-scaled distance has been established, it must be renewed in relation to the advance of quarry faces.
 
Distance
(D)
Scaled Distance (SD) limit value
SDimperial=[ft/lb0..5]
SDmetric=[m/kg0..5]
Maximum charge (W) for 8 ms delay
[ft] // [m]
[lb] // [kg]
100 // 30.48
SDi= 50//SDm= 23
0-300ft (0-90m)
4.0 // 1.814
300 // 91.44
36.0//16.326
400 // 121.92
SDi= 55; SDm= 25
301-5000ft
(91-1500m)
53 // 24.035
1000 // 304.80
331//150.108
2000 // 609.60
1322//599.527
4000//1219.20
5290//2399.015
5500//1676.40
SDi=65; SDm= 29
>5001 ft
(>1501m)
7160//3247,612
6000//1828.80
8521//3864.273
10000//3048.0
23700//10747.95
 
Table 3: Maximum amount of explosive per delay as a function of distance and SD factor
 
Blasting level chart criterion: In the fourth procedure (30CFR Section 816.67(d)(4)(i)) the blasting level chart shown in Figure 2 is to determine the maximum allowable ground vibration if the predominant frequency is known. As can be seen, for frequencies greater than 30 Hz the maximum allowable particle velocity reaches to 2 in/sec. This is related to the fact that the natural frequencies of structures are in low frequency range (4-12 Hz). This procedure is least restrictive and permits highest velocities, maximum explosive charges and shortest distances and helps to a greatest freedom in the blast design. Every shot with peak particle velocity and frequency values, however, must be monitored.
 
REDUCING OF VIBRATION EFFECTS
 
The attenuation formulas, for these two neighbour quarries with electric initiation for two rows firing presenting the site-specific vibration levels obtained. These formulas updated after 2 years according to the new location of faces and their geological conditions this time with non-electric initiation. Updated curves and their data sets are shown at the end of text in Figure 3 (number 1 for limestone and number 2 for schist quarries). Attenuation formulas are used for prediction of PPV levels depending on SD values according to OSMRE procedure III: modified scaled distance criterion. On the other hand, it is clear in Figure 3B and 3C that the vibration measurements of PPV values stay under the limits shown in Figure 3B or just on the limit as shown by an arrow in Figure 3C (White and Farnfield, 1993; Nasuf et al., 2001-2003).
 
In order to carry out more controlled application, NONEL (non-electric) system known as shock tube firing as shown in Figure 4 is used. Using different combinations of the various delay relays available, this system gives almost limitless variation of detonation patterns and delays between holes. Since the sequential delay is created between the holes rather than in the detonators themselves the system is also not limited to the number of delays.
 
It is now possible and common practice on some sites to have blasts with over 100 holes. In these applications, 500ms in-hole delay, 17ms inter-hole delays and 42ms inter-row delays are chosen like in Figure 4. By this way, the amount of maximum explosive charge per delay is reduced to 50kg and
 

 blast induced vibrations, are eliminated. The number of holes in a shot varies between 15-25 and total explosives vary 750-1250kg (Kuzu, 2003).
 
Figure 2: PPV limits and frequency values

A
 
B
C
 
Figure 3: Scaled distance versus peak particle velocities chart obtained by vibration records
(A: sample data for the line 1 and B, sample data for the line 2)
 

DISCUSSION AND CONCLUSIONS
 
Work done in these quarries shows that response to the vibrations induced by blasting which cause environmental problems are merely on human response; psychological responses to blasting. Vibrations, however, cause some trouble but have no effect on physical structures. Especially, when all the precautions are taken and a shock tube system is used, keeping the total charge in same amount, the vibration effects were minimised. In the design phase, the attenuation-formulae is used to determine charge amount per delay. Monitoring data of shots are analysed using PPV-values and their frequency relations as it is described in blasting level chart criterion of OSMRE. It is also shown that this procedure is least restrictive procedure and helps to a greatest freedom in blast design. Using this procedure, it is possible to achieve working with highest PPV-values and maximum explosive charges at shortest distances.
 
Figure 4: Dividing of charge amounts through delay arrangement by using of NONEL system
 
REFERENCES
 
1.        Anonymous, 1987, Explosives and Rock Blasting, Atlas Powder Company, Dallas.
 
2.        Anonymous, 2005, Code Of Federal Regulations, 30 CFR Part 700. http://www.osmre.gov/regindex.htm; and/or http://www.access.gpo.gov/nara/cfr/cfr-retrieve .html#page1.
 
3.        Brook, C., Farnfield, R.A., Birch, W.J., 1988, Opencast blasting and the environment, The Mining Engineer, December, pp.253-257
 
4.        Barksdale, R.D., 1996, The aggregate handbook, National Stone Association, pp. 5/16-5/25.
 
5.        Hustrulid, W., 1999, Blasting Principles for Open Pit Mining. Volume I. A. A. Balkema, Rotterdam.
 
6.        Kuzu, C. 2001. The investigation of the blast-induced vibrations occur in different formations in aggregate mines around Istanbul and the examination of the
 
 
7.        Effects of the vibrations on near residential areas”, Research Project of Istanbul Technical University.
 
8.        Kuzu, C., Hudaverdi, T., Ozturk, O., 2003, OSMRE procedures on blast induced vibrations-II, 3. National symposium for aggregate industry.
 
9.        Nasuf, E., Bilgin, N., Yigitbas, E., Kuzu, C., Orgun, Y., Yalcin, T., 2001-2003, The effects of limestone and schist quarries on Buyukcekmece Basin I-II, Project of Istanbul Technical University.
 
10.     Rosenthal. M. F., Marlock. G.L. 1987. Blasting Guidance Manual. OSMRE.
 
11.     Siskind, D.E., 2000, Vibrations from blasting, ISEE, pp. 79-82.
 
12.     White, T. J. & Farnfield, R. A., 1993, Computers and blasting. Int. Transactions of the Institution of Mining and Metallurgy. Section A. January-April 1993. p. A19-A24.

 

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