• Tunnel and Underground Space
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• v.4 no.1
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• pp.38-46
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• 1994

This paper concerns the design of blasts adjacent to structures and facilities. In order to investigate the site characteristics, measurements of in-situ wave propagation and laboratory tests of rock cores taken from the boreholes were carried out. Effects of rock media and delay intervals on ground vibration levels were identified from over sixty measurements of three times of test blasts. For practical use in the field, an empirical propagation equation was derived so as to reflect the characteristics of rock media and delay effects. Safe limits of vibration level for structures were conservatively established based on various suggested criteria. Safe limits for facilities were adopted so that vibration levels induced by blasting should not exceed the allowable limits specified in the manufacturer's installation condition. Suggested were blast pattern and operation to enhance the rock fracturing and to reduce the ground vibration levels under the restricted conditions.

• Structural Engineering and Mechanics
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• v.54 no.3
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• pp.545-560
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• 2015

In this paper, blast-induced vibration effects on buildings located in rural areas were investigated. Damages to reinforced concrete, adobe and masonry buildings were evaluated in Çatakk$\ddot{o}pr\ddot{u}$ and Susuz villages in Silvan district of Diyarbakir, Turkey. Blasting of stiff rocks to construct highway at vicinity of the villages damaged the buildings seriously. The most important reason of the damages is lack of engineering services and improper constructed buildings according to the current building design codes. Also, it is determined that, inappropriate blast method and soft soil class increased the damages to the buildings. The study focuses on four points: Blast effect on buildings, soil conditions in villages, building damages and evaluation of damage reasons according to the current Turkish Earthquake Code (TEC).

• Journal of Korean Vacuum Science & Technology
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• v.2 no.2
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• pp.97-100
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• 1998

We have investigated the effects of crystalline activation on solid phase crystallization (SPC) of amorphous silicon (a-Si) thin films. Wet blasting and self ion implantation were employed as the activation treatments to induce macro or micro crystalline damages on deposited a-Si films. Low temperature and larger grain crystallization were obtained by the applied two-step activation. High degree of crystallinity was also observed on both furnace and rapid SPC. crystalline activations showed the promotion of nucleation on the activated regions and the retardation of growth in an amorphous matrix in SPC. The observed behavior of two-step SPC was strongly dependent on the applied activation and annealing processes. It was also found that the diversified effects by macro and micro activations on the SPC were virtually diminished as the annealing temperature increased.

• Structural Engineering and Mechanics
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• v.60 no.6
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• pp.923-937
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• 2016

The common prospect in diminishing mine-blast vibration is decreasing vibration with increasing distance. This paper indicates that, contrary to the general expectancy, vibration waves change their forms when they are travelling through the low velocity layer like coal and so-called guided waves moving the vibration waves to longer distances without decreasing their amplitudes. The reason for this unexpected vibration increase is the formation of guided waves in the coal bed which has low density and low seismic velocity with respect to the neighboring layers. The amplitudes of these guided waves, that are capable of traveling long distances depending on the seam thickness, are several times higher than that of the usual vibration waves. This phenomenon can many complaints from the residential areas very far away from the blasting sites. Thus, this unexpected behavior of the coal beds in the surface coal mines should also be considered in vibration minimization studies. This study developed a model to predict the effects of guided waves on the propagation ways of blast-induced vibrations. Therefore, vibration mitigation studies considering the nearby buildings can be focused on these target places.

• Geomechanics and Engineering
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• v.18 no.2
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• pp.111-119
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• 2019

Due to certain geological characteristics (high thickness, rocky properties), some underground coal mines require the use of explosives. This paper explores the effects of fragmentation of different decks detonated simultaneously in a single borehole with the use of numerical analysis. ANSYS/LS-DYNA code was used for the implementation of the models. The models include an erosion criterion to simulate the cracks generated by the explosion. As expected, the near-borehole area was damaged by compression stresses, while far zones and the free surface of the boundary were subjected to tensile damage. With the increase of the number of decks in the borehole, different changes in the fracture pattern were observed, and the superposition effects of the stress wave became evident, affecting the fragmentation results. The superposition effect is more evident in close distances to the borehole, and its effect attenuates when the distance to the borehole increase.

• Explosives and Blasting
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• v.29 no.2
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• pp.67-80
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• 2011

Recently, the number of structure demolitions has increased in both civil and architecture fields due to various reasons such as redevelopment of a city, utilization of sites and restoration of deteriorated structures. In the past, domestic shell structures had been constructed with brick masonry and they were not high. Therefore, their demolition had been executed with ease. Recently, however, taller reinforced concrete shell structures have become a target for the destruction. Under these circumstances, how to efficiently demolish a structure and how to minimize effects of the destruction on environment including vibration and noise have become a main issue. One of the possible solutions is the explosive demolition. In this study, a case of explosives demolition of the stack, which is located in Jeju Thermal Power Plant in Republic of Korea and is 70 m tall, is addressed. In order to fall down the structure against the desired direction, 13.5 kg dynamite and 100 electric detonators were used.

• Explosives and Blasting
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• v.36 no.3
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• pp.10-18
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• 2018

The dynamic behaviour of the rock mass under the dynamic load is different from the static application of the maximum load of the same size. An experimental approach to investigating rock behavior under dynamic loads is more difficult than that under static conditions in control of dynamic loads, measurement and analysis of the results. Numerical methods are less constrained by performing the experiments numerically, rather than experimental ones, so they can be very powerful analytical tool at the design stage. However, even if the algorithms of the analysis method are appropriate, careful analysis is required because the calculation results may vary largely depending on input data and boundary conditions. In this paper, when investigating the behavior of rock structures under dynamic load numerically, the effects of boundary conditions, dynamic load and calculation time step, and dynamic load characteristics on the calculation results were reviewed to provide guidance on setting up boundary conditions and calculation time step related to dynamic analysis.

• Explosives and Blasting
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• v.22 no.3
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• pp.85-95
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• 2004

A damage criterion by blast vibration & noise has to be established through a engineering view point. Though a blast vibration has effects on human and structure, they have experienced a different damage. Thus, a damage criterion for structure needs to get a peculiar criterion which are different from one for human. At present, blast damage criterions authorized by government are Vibration & Noise Act made by Ministry of Environment and blast damage criterion of specifications for tunnel made by Ministry of Construction & Transportation. Vibration & Noise Act is based on the response of human, and while it has some application problems, it turns out to be partly rational. But, blast damage criterion of specifications for tunnel has unreasonable guidelines. In this article, its problems are reviewed and a alternative blast damage criterion is suggested.

• Explosives and Blasting
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• v.37 no.4
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• pp.26-35
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• 2019

In designing a gravity-type anchorage of earth-anchored suspension bridge, the contact friction between a blasted rock mass and the concrete anchorage plays a key role in the stability of the entire anchorage. Therefore, it is vital to understand the shear behavior of the interface between the blasted rock mass and concrete. In this study, a portable 3D LiDAR scanner was utilized to scan the blasted bottom surfaces, and rock surface roughness was quantitatively analyzed from the scanned profiles to apply to 3D FEM modelling. In addition, based on the 3D FEM model, a three-dimensional dynamic fracture process analysis (DFPA-3D) technique was applied to study on the shear behavior of the interface between blasted rock and concrete through direct shear tests, which was analyzed under constant normal load (CNL). The effects of normal stress and the joint roughness on shear failure behavior are also analyzed.

• Tunnel and Underground Space
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• v.9 no.1
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• pp.64-71
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• 1999

A numerical analysis was performed to investigate the effects of notched blasthole in controlling the fracture plane. Analyzed were elastic and elasto-plastic response of rock, and fracture propagation under static and dynamic load conditions. Results showed that the region exceeding the tensile strength extended up to three times the radius of a normal blasthole in elastic analysis, while fifteen times in elasto-plastic analysis. It was shown that a crack was driven from the notch tip up to the distance of 23 times the hole radius in the case of a notched blasthole with a notch of 5 mm in depth and 30 mm in length.