Urban Residential Area - Orica Mining Services - Next... · 2015. 6. 9. · May 22-28, 2015, Lacroma Valamar Congress Center, Dubrovnik, Croatia Fig. 13 Single Blasting and Delay

„SEE Tunnel:Promoting Tunneling in SEE Region“ ITA WTC 2015 Congress and 41st General Assembly

May 22-28, 2015, Lacroma Valamar Congress Center, Dubrovnik, Croatia

Fig. 1 Downstream portal Fig. 2 Urban Residential Section

Fig. 3 Anei River Tunnel Plame

Environmentally Low Impact Blasting Urban Residential Area

Author: Koichi SUEYOSHI, Kajima Corporation, Japan, [email protected]

Co-author: Kinya KURIKI, Toyota City municipal office, Japan, [email protected]

Co-author: Takayuki OCHIKAWA, Toyota City municipal office, Japan, [email protected]

Co-author: Toshiyuki KOSHIKAWA, Kajima Corporation, Japan, [email protected]

Co-author: Keita IWANO, Kajima Corporation, Japan, [email protected]

Hiroshi ANDOH, Orica Japan Co., Ltd, Japan, [email protected]

Topic, Conventional Tunnelling Methods in Development and Use

Keywords: electronic detonator, delay time, tunnel blasting, vibration control, MSW, deck charge

1. Introduction To reduce the load caused by tunnel blasting on environment, including psychological effects on residents, it is quite effective to reduce the blast vibration and duration of blasting time. At Anei River tunnel project, as the tunnel goes right under the residential area and it goes through stratum of hard granite, it was necessary to carry out blasting excavation, then blasting with low vibration and less sensible to human body was required. Due to the given conditions of the tunnel, the conventional blasting technique could not allow the blasting excavation but we could succeed to continue blasting excavation with new electronic detonator (eDev II) which allowed us to control the initiation delay time with very high accuracy and we could reduce the vibration sensed by human body and load on buildings. Then we continueｄ the blasting excavation of the tunnel

with understanding from residents. We would introduce how we reduce blasting vibration in this project and various information which we obtained from a series of blasting tests with this new electronic detonator, such as properties of blasting vibration, frequency characteristics of blasting vibration, relation between distance and vibration velocity etc.

2. Over view of the tunnel Anei River Tunnel is a water passage tunnel to prevent flood in the center of Toyota City(lowlands area) which is famous for automobile industry1). (Figure 1) Detailed size of the tunnel are total length 1860m, average

cross-sectional size 92.3m²(TBM(φ

6.82)36.5m²enlarged excavation

width 55.8m2), inner width 11m, inner height 7.8m. As shown in Figure 2,3 characteristics of this area are ①Slight

overburden all over the tunnel ②

Residential houses, hospital and primary school are located near the tunnel ③

Geology is very hard granite all over with small exceptional area and to keep the load on environment at minimum, TBM was used for excavation of pilot tunnel2). At the beginning, permission to use explosive was not given and mechanical



Fig. 4 Electronic Detonator (eDeVⅡ)

Fig. 5 Blast Box & Scanner (eDeVⅡ) Fig. 6 Scanning at Face Fig.7 eDeVⅡ+Explosive

Table.1 Outline of Test Blasting

excavation with hydraulic rock splitter was started. But the permission to use explosive was obtained, when we finished pilot tunnel. We carefully studied excavation speed and exposed time of residents to vibration and noise in each excavation method, we came to conclusion that blasting excavation can reduce load on environment more than other method due to very short duration of vibration and faster excavation speed. We considered limitation on blasting time and other ways to reduce effects on residents and to achieve better acceptance of residents, we needed better blasting which gives less vibration and less effects on human body.

3. Blasting by highly accurate delay time electronic detonator

For reduction of blasting vibration, it is quite effective to reduce charge volume of simultaneous shot firing, but it requires very accurate control of delay time in blasting. Then after we tried various domestic detonators, we came across highly accurate detonator from Orica (eDev3) II,Figure 4) which has many records4) in overseas.(Figure 5,6,7) A) Delay time can be set with increment of 1ms with

max. of 500 ignitions and up to 20 seconds

B) Delay time is very accurate, accuracy is ±0.01% (i.e. 0.1ms per second)

C) Only one type of detonator. Delay time setting can be done at the site with special scanner for any chosen delay time and detonation order

D) At the end of leg wire of the detonator, plastics connector is fixed, and clipping this connector on auxiliary leg wire completes the connection and risk of bad connection is minimal.

E) Detonation can be done only with the special equipment and the risk of misfire by stray current or static electricity is eliminated.

4. Blasting Test

4.1 Outline of test We carried out with highly accurate delay time electronic detonator (eDev II) a series of blasting test to collect data on blasting vibration characteristics, such as relation between distance and vibration speed and frequency at various setting of delay time. These data were to give us basic data for coming plan of blasting in urbane area. Table 1 shows outline of tests.



Fig. 8 Typical Blasting Pattern

Fig. 9 Test Blasting and Measurement Points (Plan) Fig. 10 Test Blasting and Measurement Points

Fig. 11 Measurement Point A Fig. 12 Single Blasting and Delay Blasting

Table.2 Typical Blasting Conditions

Typical blasting pattern is shown in Figure 8. As the pilot tunnel of 6.82m diameter was first excavated with TBM in Aneigawa Tunnel project, center cut at face was not required, it was advantageous for blasting vibration. In the section where blasting test has done, position of TBM in the profile changed from top drift to bottom drift and blasting pattern was required to be adjusted. Figure 9 and Figure 10 show plan and profile of the section, area next to TD300-400 was used to be quarry and stratum of this area is quite hard granite with uniaxial compressive strength of 120~ 130 MPa. As vibration measurement points, we chose 2 points, ancient quarry right above the tunnel (TD365, hereafter “point A” Fig,11) and left side of tunnel line roadside of bicycle lane (TD395, hereafter “point B”) In actual blasting, as shown in Figure 12, first 3 holes or so were single blasting with big delay time. It was to make clear separation from other blasting with normal setting of delay time.

4.2 Result and Evaluation of the Test

4.2.1 Blasting vibration waveform and frequency spectrum of each delay time

As for delay blasting, excepting first single blasts, typical time waveform and frequency spectrum of each delay time of 5ms/10ms/30ms were analyzed and shown in Figure 13. Table 2 shows blasting conditions of chosen delay time and it explains that blasting had been done under nearly same conditions. As each delay time was set with high accuracy for one hole-one simultaneous shot firing, duration of blasting was equal to (set delay time)x (number of holes). The frequency



Fig. 13 Single Blasting and Delay Blasting

Fig. 14 Distance–Vibration Speed

spectrum shows peak at inverse of delay time (in the case of 30ms, 1 second÷30ms=33.3Hz). This means that blasting had been done with high accuracy by eDev II.

4.2.2 Relation between Distance and Vibration Speed (Prediction Formula of Vibration)

In Figure 14, we show the relation between distance and vibration speed at 2 measurement points (point A and point B). In Japan, regarding the relation between distance and vibration speed5), the following formula for predicting vibration is commonly used. V=KWm/Rn When V; vibration speed (kine), K; K Value, W; Explosive for blasting (kg) R; diagonal distance (m) Normally suppliers of explosive recommend to maintain m in 0.5 ~ 1.0 and n more or less 2.06). In Figure 8, the red line was obtained with fixed values m=0.75 and n=2.0 and plotting most suitable K value calculated by least-square method. As for black lines, in this test blasting, m was fixed at 0.75 (m=0.75), one hole-one simultaneous shot firing, and explosive for all blasting was approx. 0.8kg/hole while K value and distance index n were considered as variable and multiple regression was applied. In the case of point B the red line and black line almost lay on the other and they are nearly identical. The distance index n is also more or less 2.0 (n=2.0) which was calculated by multiple regression



Fig. 16 Enlargement of wave form

Fig. 15 Distance-Vibration Speed of Single Blasting and Production Blasting

and it coincide with above mentioned formula for predicting vibration. Meanwhile at point A red line is much off the plotted line and distance index n which is calculated by multiple regression method is more or less 1.0 (n=1.0) At point A, width of tunnel (approx. 11m) and minimum overburden (approx. 10m) are nearly equal and blasting vibration arrives to measurement point Point A with wide angle of full tunnel width (approx. 11m). This is different from normal travelling mode of vibration where the vibration arrives from just one point of blasting at the face. We understood that this difference of travelling mode of vibration was the reason why index of distance n was more or less 1.0 (n=1.0), but we intend to accumulate further data through simulation etc.

4.2.3 Single Blasting Wave and Delay Blasting Wave

In Figure 15, we have plotted peaks of vibration speed of single blasting and delay blasting. We found;

(1)Vibration speed of delay blasting wave almost coincides with the top envelope line of single blasting wave. This particularity remains same with each of delay time (5ms, 10ms and 30ms). This tendency was kept same too, at both measuring point point A and point B. (2) As delay time of 5ms was the smallest among the setting of delay time, we expected increase of vibration due to the duplication of vibration wave, but we did not find much difference among different delay time (5ms, 10ms, 30ms) As a conclusion of (1) and (2), wave duplication with 5ms is as small as with 30ms. Meanwhile if number of holes was same, duration of blasting of 5ms should be simply 1/6 of 30ms. This makes significant difference of vibration sensed by human body. Therefore after a series of test blasting, we carried out basically blasting work with 5ms

4.2.4 Detailed study of delay blasting wave

In Figure 16, we enlarged delay blasting wave and confirmed peak of the wave with set delay time (in this Figure 30ms). The peak of each waveform with one hole-one simultaneous blast was not duplicated. This confirmed that blasting has been accurately controlled. As for the delay blasting waveform, vibration waveform of each set delay time shows characteristics of one hole-one simultaneous blast per hole blasting. Therefore with the longest setting of delay time and probably with the easiest for separation of



Fig. 17 Maximum value of vibration Speed of delay blasting Wave Form divided in 30ms

Fig. 18 Conceptual Drawings of Single Deck and Double Deck Fig. 19 Distance-Velocity in Double Deck

waveform, 30ms of delay time was chosen for analysis. Data of 7 delay blasts were used for analysis, firstly dividing vibration waveform with 30ms and picking up maximum value of vibration speed in each division. Figure 17 shows maximum vibration speed of every 30ms of the first 4 blasts of 30ms delay blasting. Maximum value of vibration speed is shown by the size (Norm) of 3 elements (vertical and 2 horizontal elements). From these analyses we concluded followings;

(1) Plotting of maximum vibration speed of every 30ms of each blast measured at point A and point B has been done and it always shows smaller vibration speed at point B. It seems longer distance made it so. (2) Point A and point B are in good synchronization. In other word, difference of measurement points did not affect so much on characteristics of vibration speed. We believe variance of vibration speed comes from face side (variance of explosive volume in the hole, resistance wire, geology at the face) rather than measurement points.

4.2.5 Double Deck

Double Deck is a blasting method to charge explosive at two positions in one hole (front and back), while keeping same volume of explosive as one hole-one simultaneous blast, reduction of vibration and better advance by one blasting can be achieved. Figure 18 shows concept of normal one hole-one simultaneous blast (single deck) and one hole-2 stage blasting (double deck). In double deck, to avoid sympathetic detonation and dead pressure, we separated explosive into two parts by putting aggregate instead of normal clay as stemming in between. As shown in Figure 19, vibration speed in double deck blasting is controlled in same level as single deck. Although charging operation takes more time, double deck is very effective blasting method when time or frequency of blasting is limited like right underneath the houses.



Fig. 21 Conceptual Drawings of MSW

Fig. 20 Conventional vibration evaluation method

Fig. 22 Conceptual Drawings of Seed Wave

Fig. 23 MSW Trial Point (Plan) Fig. 24 Seed Waveform

5. New Evaluation Technique for Blasting Vibration MSW

5.1 Outline of MSW

In area where many restrictions are imposed, like residential area, precise evaluation of blasting vibration is required in advance. In our project we tried new blasting evaluation technique MSW.7) MSW was developed by Dr. Rulin of ORICA and Kajima Corp. employed this method for the first time in Japan and put into actual operation of tunnel excavation. In the past, as shown in Figure 20, evaluation of blasting vibration has been done by regression curve obtained from maximum vibration speed which is calculated from maximum simultaneous blasting and distance from blasting point as parameter. Maximum vibration speed at measurement point shall be calculated from this regression curve. In MSW, waveform at new measurement point shall be predicted from seed waves at different measurement points. (Figure 21) Waveform at measurement point shall be predicted in the following process; firstly pick up a single waveform and seed wave shall be modelled; secondly seed waves shall be laid on the other; then prediction shall be done through prediction analysis of these seed waves. (Figure 22) With this predicted waveform, evaluation of blasting vibration at measurement point shall be made. Therefore it is most important in MSW to get distinct single waveform and make modelling of the seed wave. MSW facilitates to predict maximum vibration speed as well as waveform, while conventional prediction method predicts only maximum vibration speed. This means MSW gives simulation as if actual blasting was done. Then MSW gives more precise prediction than before, and much more detailed analysis in advance too, such as number of holes, location of holes, blasting order, volume of explosive

5.2 Trial of MSW

Before MSW was actually put into operation, we have done the trial. As Plane Figure 23 shows, 7 measurement points were chosen and 6 blasts were made. In order to reduce the load caused by blasting on residents, the trial was carried out at the same time with normal controlled blasting for tunnel excavation. Residue of single blast waveform of previous test blasting continued approx. 150ms. As it is the key in MSW to obtain single blasting waveform, we have done 2 single blasting with interval of 200ms between them before controlled tunnel blasting. As shown in Figure 24 seed wave was obtained before controlled tunnel blasting.



Fig. 25 Comparison of measured and MSW predicted

Fig. 27 Blasting Pattern

Fig. 26 Measurement point

In MSW trial, comparison between predicted waveform which was obtained from prediction analysis of seed waves (5 times X 7 measurement points=35 data) of 5 blasts and actually measured wave form. As the result of comparison between wave form and frequency shown in Figure 25, we could get good predicted waveform. We are confident that MSW is reliable as a new evaluation technique for basting vibration; therefore we intend to accumulate data by MSW in various circumstances in future, and to refine MSW and its accuracy.

6. Blasting right underneath of the houses

6.1 2 approaches for reduction of Vibration

Based on the result of blasting tests (TD320-TD400), before excavation arrived at tunnel section (TD859-T960) which is located right underneath of houses, we had done review of hole position and volume of explosive after every blasting. Widening excavation was done from both upstream side and downstream side. At junction section which was right underneath of houses, 2 different approaches were made. At upstream side, by synchronizing vibration waveform with position of blasting hole, we picked up the hole which had given the largest vibration and modified explosive volume, number of holes and resistance wire. At downstream side, we increased number of holes and reduced explosive volume per simultaneous blasting (MIC) for sure reduction of vibration.

6.2 Relation between Position of Blasting Hole and Vibration (Upstream side)

Tunnel excavation has been made, by using eDev II, in blasting order which was decided at the time of charging with initiation interval of exact 5ms. Synchronization of vibration waveform with position of blasting hole became possible by analysing blasting vibration wave measured on ground. As shown in Figure 26, we set up 3 measurement points at right above of tunnel in residential area. Then we measured vibration speed at each of these points. Figure 27 shows blasting holes at face and charged explosive volume at that time. Face was mini-bench form and advance by one simultaneous blasting was 1m, and charged explosive per hole was 200g, 400g and 600g. At upper arch, charged explosive was 200g per hole. At floor, advance was 2m and explosive was 800g and 1000g. Figure 28 shows blasting vibration waveform at House A and position of the hole which caused high vibration speed. Vibration speed peak 1 was also measured at House B and House C. Peak 2 was noticed at the hole position where distance from House A to the tunnel became minimum (28m)



Fig. 28 Measurement of House A Fig. 29 Measurement of House B Fig. 30 Measurement of House C

Fig. 31 Reduce MIC Fig. 32 After setting the explosives

Figure 29 shows blasting vibration waveform at House B and position of the hole which caused high vibration speed. Vibration speed peak 1 was also measured at House A and House C. Peak 2 was noticed at blast initiation hole which located at lower part of tunnel. Figure 30 shows blasting vibration waveform at House C and position of the hole which caused high vibration speed. Vibration speed peak 1 was also measured at House A and House B. Peak 2 was noticed at blast initiation hole which located at lower part of tunnel like in the case of House B. We believe from these data we can say as follows; (1) Blasting holes at arch part made by TBM give more ground vibration (2)Charge volume of bottom part holes is more or less 1000g per hole, judging from waveform, vibration from bottom is small and gives less effect to the ground

6.3 Vibration Control at right above by reduction of charge volume (downstream side)

To control vibration at right above, reduction of charge volume per hole (MIC) is effective. Reduction of MIC can be achieved by increasing number of holes at face. In Anei River Tunnel Project, as shown Figure 32, by increasing number of blasting holes and reducing MIC, blasting vibration at right above was controlled. Therefore for blasting at right underneath of houses, numbers of blast holes were increased from 200 to 300, while in other section number of blast holes kept at 100.

Figure 33 shows how charging were made in these patterns. Blasting result in residential area is shown in Figures 33 and 34 At House D (Figure 33) minimum distance from the tunnel to the measurement point on the ground was 18.3m, number of blasting holes was 240, MIC of all holes was 200g per hole. As for blasting vibration speed on the ground, PPC (Vertical) was 0.229kine as shown in Figure33. At House E (Figure 34) minimum distance from the tunnel to the measurement point on the ground was 20.6m, number of blasting holes was 230, MIC of all holes was 200g per hole. As for blasting vibration speed on the ground, PPC (Vertical) was 0.24kine as shown in figure 34.



Fig. 33 Result of Blasting at House D Fig. 34 Result of Blasting at House E

In both cases in the range over 50 Hz vibrations speed was not harmful to houses. Therefore for controlling vibration at right above, increase number of blasting holes and reduction of MIC are effective.

7. Conclusion

In Anei River Project, conventional detonators were replaced by high accuracy electronic detonators (eDev II) for reduction of vibration speed and duration of blasting time. This resulted in significant reduction of vibration felt by residents and facilitated continuation of blasting right beneath the houses and completion of the project. By series of test blasting in the section of granite we could get a lot of information and data, such as characteristics of frequency and relation between distance and vibration speed of every delay time, relation of vibration speed between single blasting and delay blasting, detailed analysis of delay blasting waveform, evaluation of double deck blasting etc. We also found usefulness of MSW through trial. As for the blasting method at right beneath houses we could collect useful actual data. These valuable information and data were made available only by highly accurate control of blasting with eDev II. Finally we would thank for good cooperation from residents nearby and close communication between operators at the site and residents nearby Reference: 1) Home page of Toyota city first class river Aneigawa refit projecthttp://www.city.toyota.aichi.jp/divisin/ah00/a12/1228169_7146.html

2) Publication of report at 69th annual meeting of JSCE on wear and tear of TBM cutter at Anei river tunnel which goes through granite geology with slight overburden by Mr. Koshikawa and others, 2014

3) eDev II Technical Data Sheet; ORICA, LTD 4) John Wall: Perimeter control utilizing electronic detonators, International Society of Explosives Engineers (ISEE), 2012

5) Kajima Publishing: Influence and countermeasures on environment by blasting vibration pp14-28

6) Gunpowder Industry Society: That blasting, such blasting p3 7) Yang, R., Wiseman, T. and D. S. Scovira, 2011, Multiple Seed Waveform (MSW) Vibration Model and Some Case Studies, International Journal of Mining and Mineral Engineering, Vol. 3, Issue 2, 2011.

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Urban Residential Area - Orica Mining Services - Next... · 2015. 6. 9. · May 22-28, 2015, Lacroma Valamar Congress Center, Dubrovnik, Croatia Fig. 13 Single Blasting and Delay