• Explosives and Blasting
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• v.28 no.2
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• pp.86-98
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• 2010

As the quality of life is being upgraded, the public complaints about noise and vibration from construction sites are growing. Despite the disputes over the blasting damage on aquatic lives in river, ocean, and aquarium near construction sites tend to increase, most of existing solutions or regulations on the damages caused by blasting are established for the damages on land. Although the estimated amount of damage is up to several millions of USD, there is no guideline for resolving the dispute related to the underwater vibration. This paper presents an example where the public grievance about the underwater noise was successfully resolved by elucidating the characteristics of underwater sound, deducing the correlations between ground vibration and underwater sound during blast, and predicting the underwater sound level during blasting from the ground vibration measured on the ground near an aquarium basin.

• Journal of the Korean GEO-environmental Society
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• v.12 no.2
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• pp.5-14
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• 2011

The most common problem encountered in domestic tunnel construction sites are solving public resentments caused by damage to adjacent structures and buildings. The most effective excavation method in rock tunnelling is the drilling and blasting, which is the main cause of vibration resulting in the public resentments. In this study, numerical analysis is conducted to compare the vibration reduction effect of line drilling and pre-splitting methods. Furthermore, the numerical simulations are verified and the results are quantified. Finally, various combinations of explosives used in controlled blasting are used and the vibration reduction effects are evaluated, thereby proving the applicability of the controlled blasting for reduction of vibration in tunnelling.

• Tunnel and Underground Space
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• v.16 no.4 s.63
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• pp.347-356
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• 2006

We analyzed case studies doing in-depth inspection of tunnel to maintain safety of existing tunnel in constructing new tunnel near to a existing tunnel with single track. Futhermore, We accomplished in-depth inspection of existing tunnel and numerical analysis. We suggested remedies to security safety of existing tunnel. We applied line drilling and pre-large hole boring method not to have an effect on existing tunnel and convinced the safety of existing tunnel from blast-vibration and blast-noise of numerical analysis. We planed to install basset system to measure displacement of existing tunnel according to excavating new tunnel.

• 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.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.279-282
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• 2008

The vertical forces in rail fasteners at areas of bridge transitions near the embankment and on the pier will occur due to different deformations of adjoining bridges caused by the trainloads. The up-lifting forces is not large problem in the blast track because the elasticity of blast and rail pad buffs up-lifting effect. But, it is likely to be difficult to ensure the serviceability of the railway and the safety of the fastener in the end in that concrete slab track consist of rail, fastener, and track in a single body, delivering directly the up-lifting force to the fastener if the deck is bended because of the end rotation of the overhang due to the vertical load. When the up-lifting force exceeds the clamp force of the fastener clip, the rail pad is out of fastener, which makes decrease the serviceability of the railway, such as noise and vibration. Furthermore, it is possible to reduce the safety of the track as the longitudinal resistance. This study is focused on guideline suggestion to decrease up-lifting force in the fastener adjacent to the civil joint of slab track of bridge throughout the parametric analysis between the vertical spring stiffness of the fastener as the material approach, the space of fastener adjacent to bridge transition, the rigidity of the girder as the geometrical approach and up-lifting force under the train load.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.2
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• pp.1-6
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• 2010

This study presents the practical design modification to improve the retracting performance of the pyro-typed high power pretensioner. 3 components of the pretensioner are redesigned and the usefulness of the design modification is verified by the experiment. During the pretensioning process, the gas blast generated from the gunpowder is transferred to the rack-pinion gear through the manifold. The rack-pinion gear is connected with the spool where the webbing is rolled up. According to the rotation of the pinion, the spool is turned and the webbing is winded. To help the gas blast flow well, the shape of the inner cross section of the manifold is changed. The spur gear design program is developed and used to find the best combination of the rack-pinion gear pair to increase the power transmission efficiency. The pinion guide is installed on the spool to prevent the vibration of the pinion. As a result of the experiment, the amount of the web retraction length is increased when every single design modification is applied. Therefore, the retracting performance of the pretensioner is considered to be improved if the presented design modifications are applied.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.541-555
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• 2020

The grouting method is used for reinforcing and waterproofing the soft ground, increasing the bearing capacity of structures damaged by lowering or subsidence due to rise and vibration, and for ordering. This study attempted to develop a blast furnace slag-based cementless grout material to increase the strength and hardening time of the grout material using reinforcing fibers. In this regard, in this study, it was used in combination with calcium hydroxide, which is an alkali stimulant of the three fine powders of blast furnace slag, and the content of calcium hydroxide was used by substituting 10, 20, and 30% of the fine powder of blast furnace slag. In addition, in order to compare the strength according to the presence or absence of reinforcing fibers, an experiment was performed by adding 0.5% of each fiber. As the content of carbon fibers and aramid fibers increased, the uniaxial compressive strength increased, and it was confirmed that the crosslinking action of the fibers in the grout material increased the uniaxial compressive strength. In addition, it was confirmed that the gel time sharply decreased as the content of the alkali stimulate increased.

• The Journal of Engineering Geology
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• v.31 no.1
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• pp.67-81
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• 2021

Grouting is used for reinforcement and waterproofing of soft ground to increase its bearing capacity, reduce the impacts of rising or lowering groundwater levels, and reduce subsidence due to vibration and general causes. This study investigated the enhancement of grout strength and hardening time by the addition of reinforcing fibers, and the development of non-cement grouting materials from blast furnace slag. An experiment was performed to measure the increase in grout strength resulting from the addition of 0.5% increments of aramid and carbon reinforcing fibers. The results show that the uniaxial compressive strength of grout increases with increasing content of reinforcing fiber. Comparison of three admixtures of finely powdered blast furnace slag and 10%, 20%, and 30% calcium hydroxide stimulating agent showed that the uniaxial compressive strength of the mixture increases with increasing content of alkaline stimulant; however, the strength was lower than for 100% pure cement. The reaction of calcium hydroxide with blast furnace slag powder, which increases the strength of the grout, is more effective if injected as a solution rather than a powder.

• Explosives and Blasting
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• v.30 no.2
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• pp.29-42
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• 2012

Variables influencing the free face movement due to rock blasting include the physical and mechanical properties, in particular the discontinuity characteristics, explosive type, charge weight, burden, blast-hole spacing, delay time between blast-holes or rows, stemming conditions. These variables also affects the blast vibration, air blast and size of fragmentation. For the design of surface blasting, the priority is given to the safety of nearby buildings. Therefore, blast vibration has to be controlled by analyzing the free face movement at the surface blasting sites and also blasting operation needs to be optimized to improve the fragmentation size. High-speed digital image analysis enables the analyses of the initial movement of free face of rock, stemming optimality, fragment trajectory, face movement direction and velocity as well as the optimal detonator initiation system. Even though The high-speed image analysis technique has been widely used in foreign countries, its applications can hardly be found in Korea. This thesis aims at carrying out a fundamental study for optimizing the blast design and evaluation using the high-speed digital image analysis. A series of experimentation were performed at two large surface blasting sites with the rock type of shale and granite, respectively. Emulsion and ANFO were the explosives used for the study. Based on the digital images analysis, displacement and velocity of the free face were scrutinized along with the analysis fragment size distribution. In addition, AUTODYN, 2-D FEM model, was applied to simulate detonation pressure, detonation velocity, response time for the initiation of the free face movement and face movement shape. The result show that regardless of the rock type, due to the displacement and the movement velocity have the maximum near the center of charged section the free face becomes curved like a bow. Compared with ANFO, the cases with Emulsion result in larger detonation pressure and velocity and faster reaction for the displacement initiation.

• Explosives and Blasting
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• v.22 no.1
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• pp.57-65
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• 2004

Explosive blasting in tunnel excavation produces ground vibration and air blast as its side effects, which may cause complaints from nearby residents. This study was intended to investigate the propagation characteristics of ground vibration induced by tunnel blasting and to evaluate its effects on the residential structures near the site. We have conducted field measurements for 6 blasts and acquired vibration data from 70 measuring points, some of which on positioned inside the tunnel for comparative reason. Various documentation was reviewed to determine an allowable level of peak particle velocity for the residential structures in the area and the allowable limit was set to 0.5 cm/sec. Propagation equations for peak particle velocities were derived from regression analyses using the data acquired at both the surface and the underground tunnel. Finally we proposed appropriate predictive equations for the two areas and a safe blasting criterion.