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

• Journal of the Korean Professional Engineers Association
• /
• v.14 no.3
• /
• pp.9-21
• /
• 1981

The rationalization for Tunnel Drifting is based on the high productivity which is achievable due to Continuous work with a Jumbo Drill, resulting in a much higher efficiency them the Conventional method of blasting, mucking and supporting services. Large projects of over 4,000m Tunnel Drifting are condidated to justify the use of a Jumbo Drill with a combination of superior explosives, machinery and techniques. During a Tunnel Drifting test, Gulita, Nabit and slurry made by Nitro Nobel were employed with following results. 1, Conditions: a. Granite Rock with Two free face b. Burden (W), 2m c. Diameter of hole, 42mm d. Depth of hole 3.5m e. Hole pitch 0.6m f. Charged Explosive per hole Gelatin Dynamite 4 pieces (112.5${\times}$4ea)+Guuita 5 pieces(110g${\times}$5ea) g. Simal-taneous Detonation h. After the blasting resultant rock size was Less 40% of the 0.3m Lumps. 2. Calculation results W=q/Wn=100cm‥‥‥Burden in simultaneous blasting 0.865kg(7.7ea)/hole ‥‥‥Amount of charge but hole pitch is 1.5W-2W The estimated cost of using a Jumbo Drill for the Construction of a 3,000,000 bbL sub-surface oil storage would be as follows: This calculation is based on the Jumbo Drill advancing 3.6m per blasting cycle. Unit cost/bbL Excavation $3.13 The attached sheet shows ideal Drilling pattern with Burn Cut & Smooth blasting method. In conclusion, it is my opinion that this method will assure safety and save cost and improve our technical know-how.

• Explosives and Blasting
• /
• v.30 no.2
• /
• pp.21-28
• /
• 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 Periodontal and Implant Science
• /
• v.38 no.1
• /
• pp.67-74
• /
• 2008

Purpose: The aim of this study was to evaluate the effect of Er:YAG laser on microstructure and roughness of $TiO_2$ blasting implant surface. Materials and Methods: Ten $TiO_2$ blasting implant were used in this experiment. One implant was control group, and nine $TiO_2$ blasting implant surfaces were irradiated with Er:YAG laser under 100 mJ/pulse, 140 mJ/pulse, and 180 mJ/pulse condition for 1 min, 1.5 min, and 2 min respectively. Optical interferometer and scanning electron microscopy was utilized to measure roughness and microstructure of specimens. Results: The surface roughness was decreased after Er:YAG laser irradiation in all groups, but there was no significant difference. 100 mJ/pulse and 140 mJ/pulse group did not alter the $TiO_2$ blasting implant surface in SEM study while 180 mJ/pulse group altered the $TiO_2$ blasting implant surface. Implant surfaces showed melting, microfracture and smooth surface in 180 mJ/pulse group. Conclusion: Detoxification of implant surface using Er:YAG laser must be irradiated with proper energy output and irradiation time to prevent implant surface alteration.

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

• Geomechanics and Engineering
• /
• v.36 no.3
• /
• pp.231-245
• /
• 2024

In recent decades, the protection and vulnerability of civil structures under explosion loads became a critical issue in terms of security, which may cause loss of lives and structural damage. Concrete retaining walls also restrict soils and slopes from displacements; meanwhile, intensive temporary loading may cause massive damage. In the current study, the modified Johnson-Holmquist (also known as J-H2) material model is implemented for concrete materials to model damages into the ABAQUS through user-subroutines to predict the blasting-induced concrete damages and volume strains. For this purpose, a 3D finite-element model of the concrete retaining wall was conducted in coupled Eulerian-Lagrangian simulation. Subsequently, a blast load equal to 500 kg of TNT was considered in three different positions due to UFC 3-340-02. Influences of the critical parameters in smooth blastings, such as distance from a free face, position, and effective blasting time, on concrete damage rate and destroy patterns, are explored. According to the simulation results, the concrete penetration pattern at the same distance is significantly influenced by the density of the progress environment. The result reveals that the progress of waves and the intensity of damages in free-air blasting is entirely different from those that progress in a dense surrounding atmosphere such as soil. Half-damaged elements in air blasts are more than those of embedded explosions, but dense environments such as soil impose much more pressure in a limited zone and cause more destruction in retaining walls.

• Economic and Environmental Geology
• /
• v.13 no.1
• /
• pp.29-50
• /
• 1980

1. 현장발파(現場發破)에 있어서 오늘날 충분(充分)히 실용(實用)할 수 있는 발파이론(發破理論)이 확립(確立)되어 있지 않다고 본다. 그 이유(理由)는 종래(從來) 사용해오던 Hauoser의 공식(公式)이 실용발파(實用發破)에 전(全)혀 도움을 주지 못하기 때문이다. 즉(卽), i) 장약량수정(裝藥量修正)에 관(關)한 누두함수(漏斗函數) f(n) 발파규모수정항(發破規模修正項) f(W)와의 혼용(混用) ii) 암석항력계수(岩石抗力係數) g와 단위체적당폭약소비량(單位體積當爆藥消費量) $(kg/m^3)$과의 오용(誤用) iii) 폭파계수(爆破係數) C가 egd인가, f(W) egd인가의 부명확성(不明確性) 등이다. 본연구에서의 이와 같은 제문제점(諸問題點)을 명확(明確)히 하고 2. 제발발파이론(齊發發破理論)을 확대적용(擴大適用)하여 bench 발파(發破), smooth blasting 및 소할발파(小割發破)에 있어서는 장약량공식(裝藥量公式)을 유도(誘導)할 수 있음을 증명(證明)하고 3. 갱도굴착단면계수(坑道掘鑿斷面係數) 및 발파규모(發破規模)에 의하여 수정(修正)한 단위체적당장약량(單位體積當裝藥量)$(kg/m^3)$을 구(求)하고 총장약량(總裝藥量)을 산출(算出)하여 발파설계(發破設計)를 할 수 있는 방법(方法)의 예(例)를 들어 보였다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.22 no.3
• /
• pp.529-539
• /
• 1998

A quantitative study of impact damage of ${Al_2}}O_3}-TiO_2$ plasma coated soda-lime glasses was carried out and compared with that of the uncoated smooth glass specimen. The shape of cracks by the impact of steel ball was observed by stereo-microscope and the decrease of the bending strength due to the impact of steel ball was measured through the 4-point bending test. At the low velocity, cone cracks were occurred. As the impact velocity increases, initial lateral cracks were propagated on the slanting surface of a cone crack, and radial cracks were generated at the crushed site. When the impact velocity of steel ball exceeds the critical velocity, the contact site of specimen was crushed due to plastic deformation and then radial and lateral cracks were largely grown. Crack length of coated specimens was smaller than that of uncoated smooth specimen due to the effect of coating layer on the substrate surface. According to impact velocity, the bending strength of coated specimens had no significant difference, compared with that of the uncoated smooth specimen. But this represents that the bending strength of coated specimens was increased, considering the effect of sand blasting damage which was performed to increase the adhesion force of coating layer.

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

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.8 no.4
• /
• pp.20-27
• /
• 2009

The characteristics of titanium alloy as a relatively advanced material is low density, avirulent and, superior corrosive resistant, therefore the use of titanium alloy is increasing lately in aerospace and mechanical technologies, precision machinery, electronics industry, petro-chemical industries and biomedical areas. In these days, the titanium alloy product is required various surface qualities of not only smooth surface but also rough surface depending on usages. The purpose of this experimental research is to find the optimum surface roughness of titanium alloy of Ti-6Al-4V, by micro abrasive blasting as depending variable conditions of working pressure, nozzle size, working time, stand of distance and power particle size.