• Tunnel and Underground Space
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• v.16 no.6 s.65
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• pp.476-485
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• 2006

During blasting, both shock wave and gas are generated in detonation process of explosives and the generated wave and gas expansion may create new fractures and damage rock mass. In order to explain and understand completely the fracture mechanism by blasting, we have to consider both effects of the wave and gas expansion simultaneously. In this study, we use a discrete element code, PFC2D and develop an algorithm which is capable of modeling both detonation and gas pressures acting on blasthole wall and visualizing generated cracks within rock mass. Moreover, the gas-pressure modeling method which applies a corresponding external force of gas pressure to parent particles of radial fractures is adopted to simulate a coopting between rock mass and gas penetrating created radial fractures. The developed algorithm is verified by reproducing numerical simulations of a lab-scale test blast successfully.

• Tunnel and Underground Space
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• v.22 no.1
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• pp.54-59
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• 2012

Deformation of Lead plate blast pressure meter were measured after they were exposed to surface blasting. Blasting pressure was determined by comparing the data with calibration graph which was drawn from the laboratory experiments with gas gun of Hopkinson bar tester. The results were compared with calculated values from the equations of CONWEP (Conventional Weapons Effects Program) and DDESB (Department of Defence Explosives Safety Board). Measured values were lower than calculated values in near field. Gradual decaying tendency of the pressure was observed. It means that estimated blasting pressure of very near field with theoretical equations can be uncertain.

• Geomechanics and Engineering
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• v.7 no.6
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• pp.613-631
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• 2014

To complement the method of field-scale seismic ground motion simulations by buried blast techniques, the application and evaluation of the capability of a numerical modeling platform to simulate buried explosion-induced ground motion at a real soil site is presented in this paper. Upon a layout of the experimental setup at a level site wherein multiple charges that were buried over a large-diameter circle and detonated in a planned sequence, the formulation of a numerical model of the soil and the explosives using the finite element code LS-DYNA is developed for the evaluation of the resulting ground motion and surface subsidence. With a compact elastoplastic cap model calibrated for the loess soils on the basis of the site and laboratory test program, numerical solutions are obtained by explicit time integration for various dynamic aspects and their relation with the field blast experiment. Quantitative comparison of the computed ground acceleration time histories at different locations and induced spatial subsidence on the surface afterwards is given for further engineering insights in regard to the capabilities and limitations of both the numerical and experimental approaches.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.1
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• pp.48-54
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• 1999

A method was disclosed for making phase stabilized ammonium nitrate(PSAN), where the process involves precipitation of ammonium nitrate(AN) with potassium dinitramide(KDN) from the aqueous solutions of their salts using a salting out technique. The organic solvent used as a precipitant was acetonitrile. The DSC results showed that the precipitates are PSAN, and AN is stable over the temperature range from $0^{\cire}C$ to $80^{\cire}C$ if the KDN concentration in the precipitated solids is greater than about 6 wt.%. The particles prepared are expected to be useful as an oxidizer for the solid rocket propellants and explosives.

• Journal of Industrial Technology
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• v.3
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• pp.17-26
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• 1983

The blast vibrations were measured from 10 places through Seoul subway area to study their effects on the structures and to establish the safe blasting limits. For purpose of the present study, particle velocity only was recorded and analyzed, because it correlated most directly with damage. The results are as follows: (1) The proagation equation, $V=K(D/W^{1/3})^{-n}$ was obtained. Typical values could be found for n range from 1.7 to 1.5 and for k range from 48 to 138. (2) From the relationship between schmidt hammer rebound hardness and uniaxial compressive strength, $Sc=0.514{\times}(S.H)^{0.23}$, the compressive strength at any area can be assumed. (3) The use of AN-FO and other explosives with low detonation pressure may reduce vibration levels generated.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.10a
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• pp.155-159
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• 2009

Crack-controlled method which utilizes the dynamic energy such as explosives and propellent gases have been applied to the development of mineral resource and oil and civil engineering. It is necessary to consider the fracture processes associated with the material properties and external forces to control crack propagation using borehole pressure. To investigate the influence of the applied borehole pressure waveform on the crack propagation in rock masses having different material properties, a no-free surface model was used, consisting of a borehole in rock with a continuous boundary. Loading rates ranging from 1 to 100MPa/${\mu}s$ with different rock mass properties was employed to investigate the loading rate dependency of fracture patterns in the rock mass.

• Proceedings of the Korean Society of Toxicology Conference
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• 2002.05a
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• pp.98-98
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• 2002

Di-n-butyl phthalate(DBP) is one of the most commonly used phthalic acid esters(PAEs). It is extensively used as a plasticizer in elastomers and explosives, as a solvent for printing inks and resins and as a textile lubricating agent. It is also present in the formulations of various cosmetic products.(omitted)

• Journal of Industrial Technology
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• v.26 no.A
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• pp.17-28
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• 2006

In underground drilling and blasting, particularly in small headings(generally under $20m^2$), the prospects for changes of blast parameters are usually more limited than those employed by large area tunnel(over $20m^2$). It is also well known that the consumption of explosives and specific drilling rate for small tunnel areas are exponentially increased also tunnel areas decrease. To confirm above results, some tests for two tunnels(irrigation water tunnel with $6.0m^2$ area, electric supplies tunnel with $15.0m^2$) are also carried out in this study. As a results, specific drilling rate and specific charge for irrigation water tunnel were decreased from 13.8 to $7.7m/m^3$ and from 4.88 to $2.56kg/m^3$ respectively. Those for electric supplies tunnel were also decreased from 8.0 to $4.9m/m^3$ and from 3.46 to $2.22kg/m^3$.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.3 s.18
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• pp.129-139
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• 2004

DXD-19 is a flexible sheet explosive, which is a new polymer-bonded explosives(PBX's). DXD-19 is relatively insensitive and can be extruded into various configurations to be applied to munitions. A typical application includes multi-point initiation for the warhead, cutting/severance devices and transfer lines. The DXD-19 composition employs a binder system derived from the thermoplastic elastomer(HyTemp 4454) containing $5\%$ OH terminated with isocyanate curable for increasing mechanical properties. The use of an elastomer CAB increases its mechanical properties and the use of an energetic plasticizer BDNPF/BDNPA(F/A) improves the process ability as well as energy contents. The composition of the extruded DXD-19 formulation is formed $\%$ weight of $PETN/HyTemp/ATEC/(F/A)/CAB=72\~73/12\~13/6\~7/6\~7/1\~2$. Our safety tests of DXD-19 shows Insensitivity to an impact test and friction test, good thermal stability and excellent mechanical properties.

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