• Geotechnical Engineering
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• v.11 no.3
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• pp.55-68
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• 1995

This paper is the analysis of the relationship between RQD and decay constant, blasting vi bration constant of cube root scaling and square root scaling, through experimental blast ins test in subway construction for excavation of shaft hole by bottom blasting. The magnitude of particle velocity is largely effected by the distance from blasting source, the maximum charge per delay and the properties of ground. In order to verify the effects of ground properties on blast-induced vibration, the relation-ship between magnitude of blasting vibration and Rock Quality Disignation which stands for joint property was studied. The results of test are verified that blasting vibration constant "K" and the absolute value("n") of decay constant relatively increse as RQD increased. According to the result, it can be predict the particle velocity by the blast -induced vibration in bottom blasting pattern.om blasting pattern.

• Explosives and Blasting
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• v.34 no.2
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• pp.18-30
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• 2016

A drill & blasting method using explosives is the most efficient way to break the rock in the urban projects. However, the blasting method cause vibration, noise and fly-rock as blast pollutions so that blasting wroks are restricted by adjacent structures such as apartment and residence houses. To conduct blasting works at near structures, the numbers of blast-holes a blast and the size of the blast are limited by kinds of detonators and initiation methods. So, the production rate is reduced and the construction period should be increased. Therefore, in this case the deck-charge blasting methods using available detonators in domestic market were designed and evaluated in order to confirm the application possibilities in specific urban sites.

• Tunnel and Underground Space
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• v.5 no.2
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• pp.134-143
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• 1995

Effects of blasting vibrations on curing concrete have not been well studied. As a result, unreasonable and strong blasting vibration constraints have been placed on blasting when it occurs in the vicinity of curing concrete. To study the effects of blasting on curing concrete blocks of 33.3X27.7X16.2 cm were molded and placed on the quarry. Several sets of concrete blocks were subjected separately to peak vibrations of 0.25, 0.5. 1.0, 5.0, and 10cm/sec. The impulses of blasting vibrations were applied with thirty-minute intervals. Along with unvibrated concrete blocks, the vibrated concrete samples cored with 60.3 mm in diameter were measured for elastic moduli, sonic velocity and uniaxial compressive strength. Test results can be summarized as follows; 1. The blasting vibrations between 6 and 8 hours after pour generally lowered on the uniaxial compressive strength of the concrete. 2. A low blasting vibration of 0.25 cm/sec did not affect the uniaxial compressive strength. As the magnitude of the blasting vibration increases, compressive strength of concrete is decreased. 3. Physical properties of the P-wave velocity, Young's modulus, and Poisson's ratio showed a weakly decreasing trend in the concrete blocks vibrated between 6 and 8 hours after pour.

• Tunnel and Underground Space
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• v.16 no.3 s.62
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• pp.232-240
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• 2006

In this paper, the blasting load has been calculated using Input Identification method and measured data in borehole blasting to reflect the exact blast behavior and soil vibration. The fitness of calculated blasting load is examined by comparing measured data and results of numerical analysis. According to the results, blasting load estimated by Input Identification method was more adequate than proposed blasting pressure equation in the reflection of blast behavior and soil vibration. In addition, it showed more reasonable results at the evaluation of structure's vibration in the 3D finite element method.

• Explosives and Blasting
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• v.41 no.4
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• pp.29-40
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• 2023

Rock blasting is utilized in various fields such as mining, tunneling, and the construction of underground structures. The role of rock blasting technology has became increasingly significant with the growing utilization of underground cavity. Blast hole pressure, generated during rock blasting, is a critical variable directly impacting factors such as crushing and blast vibration. It stands out as one of the most important parameters for assessing explosive performance and predicting blasting effects. While blast hole pressure has been studied by several researches, comparisons are challenging due to variations in experimental conditions such as explosive type, charge, and blasting conditions. In this study, blast hole pressure sensors and observation hole pressure sensors were developed to measure pressure during single-hole blasting, The experimental results were then used to discuss the propagation characteristics of pressure around the blast hole and the corresponding blast vibration.

• Explosives and Blasting
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• v.41 no.3
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• pp.13-25
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• 2023

The conventional bench blasting method uses the bottom initiation in all blast holes in a round, whereas the MDS (mixture detonation system) method applies the bottom and top initiations alternately according to the spatial position or temporal sequence of each blast hole. The former and latter are respectively called the SMDS (spatial MDS) and TMDS (temporal MDS) methods. Another variant called MMDS (modified MDS) is designed for the specific use in the site having a fly-rock problem. This study compares the MDS method to the conventional method in the aspect of rock fracturing effect. The comparison is made by numerical simulations for a two-row bench blasting model in the LS-DYNA. The SPH-FEM coupling method is utilized for constructing the blasting model. The SPH elements are used for the rock in the near-field region of the blast holes, and the FEM elements for that in the far-field region. The RHT material model is used for the rock. As a result of the simulations, it was found that up to 0.4 m deeper damaged zone was appeared in the SMDS method than in the conventional method for the case of the burden 1.6 m and bench height 3.0 m. In addition, the fly-rock velocity to the normal direction of the bench slope was appeared about 2.0 m/s lower in the MMDS method compared to the other methods.

• Tunnel and Underground Space
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• v.4 no.3
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• pp.228-236
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• 1994

• Explosives and Blasting
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• v.28 no.2
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• pp.1-16
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• 2010

This study focuses on the phenomenon that the blast damaged zone developed on rock slope surfaces can be affected by joint characteristics rather than by explosive power when the pre-splitting is applied to excavate a jointed rock slope. The characteristics of rock joints on a slope were investigated and categorized them into 4 cases. Also an image processing system has been used for comparing the distribution pattern of rock blocks. From this investigation, it was found that the rock blocks bigger than 2,000 mm occupied 42% in the case of single joint set and it showed the well efficiency of pre-splitting blast. In cases of 2~3 parallel joint sets and 2~3 intersecting joint sets are developed on rock surfaces, the rock blocks in the range of 1,000~2,000 mm occupied 43.6% and 35.8%, respectively, and it showed that the efficiency of pre-splitting was decreased. When more than 3 joint sets are randomly developed, however, the rock blocks in the range of 250~500 mm occupied 35% and there was no block bigger than 1,000 mm. This denotes that the blasting with pre-splitting was not effective. The numerical analysis using PFC2D showed that the blast damaged zone in a rock mass could be directly influenced by the pre-splitting. It is, therefore, required to investigate the discontinuity pattern on rock surfaces in advance, when the pre-splitting method is applied to excavate jointed rock slopes and to apply a flexible blating design with a consideration of the joint characteristics.

• Explosives and Blasting
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• v.20 no.2
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• pp.7-19
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• 2002

The cut is placed high up in the section, the 1st sloping holes below the cut, and divided all the holes located below the 1st sloping holes into a certain area with longitudinal section, to lower pollution made from tunnel blasting. With the sequential blasting machine, after I first blasted holes around the cut holes by a pre-splitting method, blasted the cut area and the 1st sloping holes. The 1st and 2nd sloping holes divided areas are initiated gradually to free face upwards made by the cut. Especially, I pre-splinted contour holes previous blast the before sloping holes from the contours. The ground vibration from the earth surface just over the advance face decreased about 42.0% compare with the down blasting method under the condition of equal charge weight per delay. I controlled the crack and over break of the mother rock by pre-splitting contour holes before blast the first sloping holes from the contours. The peak values of noise and air blast by blasting decreased about 10dB more than the down blasting method. the noise and air blast diminished gradually as a round. The throw distance of the fly rock was decreased about 55%.

• Explosives and Blasting
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• v.23 no.1
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• pp.55-64
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• 2005

Safe and cheap emulsion explosives have recently replaced the existing CD explosives in order for people to reduce the prime cost and to prevent the safety accidents from happening in construction and civil engineering sites. However, the emulsion explosives have been in reality fared with difficulties in terms of the blasting force when using them in the tunnel constructed in the rock mass composed of hard rock. In this regards, this study is to verify their blasting efficiency and possibility of construction by applying MegaMEX, one of the high performance Emulsion explosives, to the rock mass of hard rock. In terms of their blasting efficiency such as advance ratio and fragmentation, it has turned out that they have overcome the limit of the existing Emulsion explosives and they have had the equivalent level of MegaMITE, one of the GD(Gelatin dynamite) types of explosives while they have been also advantageous to the environmental aspects.