• Explosives and Blasting
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• v.23 no.1
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• pp.19-30
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• 2005

In this study, the standard particle velocity equations and the equation for calculating specific charge weight with application of rock fracture method using the finecker plus are suggested and the existing equation of fragmentation was transformed into one applicable to finecker plus. Standard rock fracture pattern was designed. Square root scaled equation is $V=345.39(D/\sqrt{W})^{-1.4484$. computable equation to specific charge wei인t is $W_f=(2.3\~2.5)\;f_agdV$, charge weight per hole is 0.54kg, and proportion of diameter 30cm fragmentation is about $48.7\%$. This rock fracture method nay him out to be more excellent than the other methods.

• 한국지구물리탐사학회:학술대회논문집
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• 1999.08a
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• pp.48-64
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• 1999

For quantitative evaluation of geotechnical engineering properties such as rippability and diggability, clear interpretation on the subsurface velocity structures should be preceded by figuring out top soil, weathered and soft rock layers, shape of basement, fracture zones, geologic boundary and etc. from the seismic refraction data. It is very important to set up suitable field parameters, which are the configuration of profile and its length, spacings of geophones and sources and topographic conditions, for increasing field data quality Geophone spacing of 3 to 5m is recommended in the land slope area for house land development and 5 to 10m in the tunnel site. In refraction tomography technique, the number of source points should be more than a half of available channel number of instrument, which can make topographic effect ignorable. Compared with core logging data, it is shown that the velocity range of the soil is less than 700m/s, weathered rock 700${\~}$1,200m/s, soft rock 1,200${\~}$1,800m/s. And the upper limit of P-wave velocity for rippability is estimated 1,200 to 1,800m/s in land slope area of gneiss. In case of tunnel site, it is recommended in tunnel design and construction to consider that tunnel is in contact with soft rock layer where three lineaments intersecting each other are recognized from the results of the other survey.

• The Journal of Engineering Geology
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• v.11 no.2
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• pp.163-174
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• 2001

For quantitative evaluation of geotechnical engineering properties such as rippability and diggability, clear interpretation on the subsUJiace velocity structures should be preceded by figuring out top soil, weathered and soft rock layers, shape of basement, fracture zones, geologic boundary and etC. from the seismic refraction data. It is very important to set up suitable field parameters, which are the configuration of profile and its length, spacings of geophones and sources and topographic conditions, for increasing field data Quality. Geophone spacing of 3 to 5m is reconunended in the land slope area of house land development site. In refraction tomography technique, the number of source points should be more than a Cluarter of available channel number of instrument and the subsurface structure interpretation can be decreased the artifact of inversion by topographic effect. Compared with core logging data, it is shown that the velocity range of the soil is less than 700m/s, weathered rock 700~1,200m/s, soft rock 1,200~1,800m/s on the velocity tomogram section. And the upper limit of P-wave velocity for rippability is estimated 1,200 to 1,800m/s in land slope area of gneiss.

• Tunnel and Underground Space
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• v.18 no.1
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• pp.33-43
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• 2008

The techniques for measuring the bulking factor of rock mass in subsidence area have never been well known all over the world. The volumetric expansion ratios obtained from blasting operation were the only way of acquiring the bulking factor of rock mass. The bulking factor of rock mass obtained from blasting operation, however, has been seldom classified in a certain criterion. Also the bulking factor of rock mass can be very dependent upon rock types. In order to overcome this limitation obtained from these reasons, the authors studied the experimental bulking factor of rock mass according to the stacking shapes as well as the overburden stresses. Gneiss, limestone and shale were chosen for testing specimens, and each bulking factor has been measured with laboratory test of applying a constant load on the fragmented rock specimens.

• Tunnel and Underground Space
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• v.21 no.1
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• pp.82-92
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• 2011

Stereophotogrammetry is used to extract spatial information of an object by constructing a stereo-image from two or more photos. In this study, stereophotogrammetry was adopted for analyzing blast fragmentation of rock blocks in a quarry site. 2D image processing and stereophotogrammetry were applied to the fragmentation analysis of rock blocks horizontally scattered in a laboratory, and their results were compared with physical measurements using a water tank. Fragmentation of rock muckpiles was estimated in laboratory and field tests by using the stereophotogrammetry and statistical analysis.

• Explosives and Blasting
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• v.23 no.1
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• pp.9-17
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• 2005

This study is to clarify the comparative relationship and mechanical anisotropy of granite distributed in the Nam-weon on the subject of weathered rock mass sea water surroundings. Artificial weathering test is defined as a test, which controls the weathering rate and agents by controlling the weathering rate and agents by artificial environmental of salt water. Increased weathering degree is large indicated by weathering salt water, such as apparent specific gravity, absorption, porosity, uniaxial compression strength, P-wave velocity, slake durability, shore hardness, indirect tensile strength(brazilian test) and cohesion were measured. As the Weathering salt water proceeds, cracks develope increasingly. A number the cracks affect the rock deformation. Therefore, stress-strain curve of weathered salt water rock in one confined state are quite differ from weathered fresh water rock those. A reason of their deformation type is the formation of micro-cracks and potential porosity caused by artificial weathering test.

• Explosives and Blasting
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• v.27 no.1
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• pp.7-20
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• 2009

In this study, 5 steps of different delay intervals are applied to a plasma rock-breaking machine that is driven by electric shocks in order to improve the workability of the traditional single-shot type plasma rock-breaking operation. The sequential steps use the electrolyte volume per delay of 1, 2, 3, 4, 5 kg and it has been analyzed to measure the delay time and level of the ground vibration and noise according to exploding. The delay time of the rock-breaking machine by an electric shock of 5 steps has used about 40~50ms at the electrolyte connected from 1 to 3 holes, about 70~80ms at the electrolyte connected from 4 to 5 holes. It is identified that the extents of the ground vibration is low to 1 over 3~6 compared with that of the emulsion explosives.

• Tunnel and Underground Space
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• v.11 no.3
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• pp.248-256
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• 2001

The cylindrical cut is most frequently used in tunnel blast regardless of their dimensions. In this study the new parallel cut is proposed to raise advance per round, which is considered to be an elevation of the traditional cylinder cuts. The general geometric pattern of a new cut with parallel blast holes is proposed. The detailed burden and spacing between the central blasthole and those of the four section are also given. The blast results between new cut and traditional cylinder cut are given. The main results of this study are as follows. 1) The average advances per rounds in new cuts can reach 99.5% of drilling length. That of traditional cylinder cuts are known approximately 90∼95% 2) Specific charge weight of new cut compare to that of cylinder cut is approximately reduced 5% from 1.363 to 1.297 kg/㎥ 3) Specific drilling rate is also reduced 8% from 2.393 to 2.130 m/㎥ 4) Vibrations, fly rock, and fragmentation produced by the new blast are to be proved superior to those of the traditional cylinder cuts.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.303-310
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• 2002

Overbreak occurred inevitably in a tunnel excavation, Is the main factor for increasing cost and time in tunnel projects. Furthermore the damage to the remained rock mass related to the overbreak can give rise to a serious safety problem in tunnels. As a rule of thumb, causes for the overbreak are inaccuracy in drilling, the wrong design of blasting and selection of explosives, and heterogeneity in rock mass. Specially, the geological features of the rock mass around periphery of an excavation are very important factors, so a lot of researches have been conducted to describe these phenomena. But the quantitative geological classification of the rock mass for the overbreak and the method for decreasing the amount of the overbreak have not been established. Besides, the technical improvement of the charge method is requested as explosives for the smooth blasting have not functioned efficiently. In this study, the working face around periphery of an excavation has been continuously sectionalized to 5∼6 parts, and the new Blastability Index for the overbreak based on 6 factors of RMD(Rock Mass Description), UCS(Uniaxial Compressive Strength) JPS(Joint Plane Spacing), JPO(Joint Plane Orientation), JPA(Joint Plane Aperture) and FM(Filling Material) is proposed to classify sections of the working face. On the basis of this classification, the distance between contour holes and the charging density are determined to minimize the overbreak. For controlling the charging density and improving the function of explosives, the New Deck Charge(N.D.C) method utilizing the deck charge method and detonation transmission in hole has been developed.

• Explosives and Blasting
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• v.39 no.2
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• pp.1-14
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• 2021

Recently, with the development of high-performance processing devices such as GPGPU, a three-dimensional dynamic analysis technique that can replace expensive rock material impact tests has been actively developed in the defense and aerospace fields. Experimentally observing or measuring fracture processes occurring in rocks subjected to high impact loads, such as blasting and earth penetration of small-diameter missiles, are difficult due to the inhomogeneity and opacity of rock materials. In this study, a three-dimensional dynamic fracture process analysis technique (3D-DFPA) was developed to simulate the fracture behavior of rocks due to impact. In order to improve the operation speed, an algorithm capable of GPGPU operation was developed for explicit analysis and contact element search. To verify the proposed dynamic fracture process analysis technique, the dynamic fracture toughness tests of the Straight Notched Disk Bending (SNDB) limestone samples were simulated and the propagation of the reflection and transmission of the stress waves at the rock-impact bar interfaces and the fracture process of the rock samples were compared. The dynamic load tests for the SNDB sample applied a Pulse Shape controlled Split Hopkinson presure bar (PS-SHPB) that can control the waveform of the incident stress wave, the stress state, and the fracture process of the rock models were analyzed with experimental results.