• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.1
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• pp.49-57
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• 2013

The conventional blasting method generates serious blasting vibration and underbreak/overbreak in spite of its high efficiency for rock excavation. To overcome these disadvantages, this paper introduces an alternative excavation method that combines the conventional blasting process with the free surface on the perimeter of the tunnel face using waterjet cutting technology. This proposed excavation method has advantages of (1) reducing vibration and noise level; (2) minimizing underbreak and overbreak; and (3) maximizing excavation efficiency. To verify the effects of the proposed excavation method, field tests were performed with a smooth blasting method at the same excavation conditions. Test results show that the vibration is reduced by up to 55% and little underbreak/overbreak is generated compared with the smooth blasting method. In addition, the excavation efficiency of the proposed method is greater than that of the smooth blasting method. The proposed blasting method with a free surface using waterjet cutting can be applied to urban excavation construction as well as to underground structure construction.

• Explosives and Blasting
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• v.23 no.4
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• pp.1-18
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• 2005

The underground research tunnel, which is under construction in KAERI for the validation of HLW disposal system, is excavated in a granite rock by drill&blasting. In order not to disturb the operation at the research facilities including Hanara reactor by the blasting for the excavation of $6m{\times}6m$ tunnel, a test blasting at the site was performed. Using the vibration equation derived from the test blasting, it was possible to predict the vibration at different locations at KAERI and to conclude that the blasting design would meet the design criteria at the major facilities in KAERI. The noise and vibration generated by the main blasting were continuously measured. In the case of vibration, the measured values were lower than the predicted one from the vibration equation. It is, therefore, concluded that the influence of blasting work for the construction of 280m long research tunnel on the major facilities in KAERIl would be insignificant.

• Explosives and Blasting
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• v.30 no.2
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• pp.21-28
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• 2012

Blasting methods are frequently used in case of forming slope artificially like slope cutting and open-cut method in the downtown area because of many economical and effective advantages. It is important that blasting work is carried out maintaining original strength of rock and not to damage rock face. And it is also considered that blasting method to decrease ground vibration is essential to the point of blast damages due to the ground vibration. In this study, to form a smooth plane of rock slope face, many trial blasts were carried out in this way that explosives were installed in detonating cord by equal interval in different charging method and stemming method. Using 4 blasting patterns in total 60 blast holes and 20 times of blasts were carried out. At the same time ground vibration measurements were carried out 15~102m away from the blast source, and total number of 310 data were obtained. Measured data for ground vibration velocity were analyzed so as to study blasting method to protect slope plane while decreasing blast vibration in an effective way.

• Journal of the Korean Professional Engineers Association
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• v.18 no.3
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• pp.1-20
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• 1985

The traffic congestion of Seoul city has been one of the most serious problems to be settled since the advent of 1970s. As a means to mitigate traffic mess, the authority concerned launched the construction of subway line 3 and 4 in 1980. The two Subway lines slated for completion by 1985 cross each other and run north-south direction, passing through the metropolitan area of Seoul city fraught with high-rise edifices and large-scale shopping centers, and, in order to reduce blasting vibration, NATM was executed for a distance of 10 Km, instead of ASSM previously employed when subway line 1 and 2 were constructed. Tunnel blastings were implemented, preceded by classifying the rocks at construction area into five categories, namely, hard rock, semi-hard rock, weak rock weathered rock and silt and by calculating their respective specific charges through standard test blastings, by employing the pre-splitting and smooth blasting with drilling patterns of burn cut type, so as not to cause damages to surface structures. Most of explosives used were the slurry of low specific gravity and low velocity, and the firings executed by the use of milli-second detonators. Empiric formula were also formulated to check blasting vibrations, based on the vibration allowable values of West Germany standard, for the application to vulnerable construction zones. Should the two lines be placed for public service in 1985, about 40% of the total traffic population of Seoul city amounting to 15 million as of 1984 is estimated to be carried by subway with no difficulties.

• Journal of the Korean Professional Engineers Association
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• v.16 no.3
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• pp.5-23
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• 1983

On the Seoul Metropolitan Subway Construction of No. 3, 4 Line, the total length is 57 Km and it is now undergoing almost 55％ progress. The working method is classified into Open Cut of 70% and the rest of 30% tunnelling method in the 48 job site. Above tunnelling method is execute by American Steel Support System and the rest of 10 job site carried out by New Austria Tunnelling Method. This paper describes Blasting Standardizations works on the above Tunnelling ' Open Cut Method under big slogan, first safety, second execution. As a superintendent, I strived standardization of works with Better powder, Better Drills ' Better Pattern. Geological structure of Seoul area is composed by Jurassic Granite and also the above rockgroup are over burden by Alluviums as a Unconformity. First of all, I carried out the standard amount of powder and burden through experimental standard blasting by each powder as following Blasting works in the subway construction is surrounding shop Building, under pass the city river and also under pass highest building basement floor. I made allowable Blasting Vibration Value by West-Germany Vornorm DIN 4150, Teil 3 and should measure each blasting works as fellows all of powder is used basically Low-Gravity and Low Velocity such as Slurry, Ammonium Nitrate ' Finex I, II. for Smooth Blasting Instead of Gelatin Dynamite. Electric Detonation Cap is used basically M/S Delay Cup instead of Electric delay ' Simultaneous cap. I applied following formula V=KW3/4 $D^{-2}$ V=Particle Velocity (Cm/sec) K=Ginh Huh's Value W=Delay Charge (Kg) D=Distance(m) In the Open Cut, within 1m distance from H-pile I made to use the Concrete breaker, as following V=7W/$^{0.5}$V/$^{-1.75}$ On the Concentrate Building area, I advise to use Light class drill ø36m Bit and advance 1.1m per round blasting the three boom jumbo drill over ø45mm used only suburb of city.e Light class drill ø36m Bit and advance 1.1m per round blasting the three boom jumbo drill over ø45mm used only suburb of city.

• Tunnel and Underground Space
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• v.3 no.1
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• pp.54-62
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• 1993

In order to evaluate the necessity for the support during the excavation of the transport drift and use the data for design applications, laboratory testings of mechanical properties of rock samples and engineering rock mass classifications on this study site were performed. The values of RMR and Q-system are 68 and 11.8, respectively. Since these results were evaluated as good, this rock mass were determined to be unsupported. Full face excavation method was determined to be suitable for excavating this drift. In case of excavation, smooth blasting techniques must be carried out at the wall rock and the crown. However, considering the blast vibration etc. that have an effect on the surrounding rock mass, approximately less than 9kg of explosive charges per blast should be maintained.