• Explosives and Blasting
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• v.32 no.3
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• pp.10-17
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• 2014

In this study, the effect of the hole spacing and the detonation delay time in the long hole blasting of two free surface rock mass on the variation of the principal strains in the vicinity of blasting holes is investigated by use of the finite element program, Visual FEA. The cross section perpendicular to blasting holes is modelled and the maximum principal strains at some major points in the cracking zone are examined. As a result, it was found that the maximum principal strain in the cracking zone becomes larger in the long hole blasting with the narrower hole spacing and the longer detonation delay time. The maximum principal strain was affected by the detonation position in charge hole.

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.2
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• pp.197-208
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• 2022

The existence of shallow bedrock and the desire to use underground space necessitate the use of blasting methods. The standard blasting method under water after drilling is associated with certain technical difficulties, including reduced detonation power, the use of a fixed charge per delay, and decoupling. However, there is no blasting method to replace the existing blasting method. In this paper, a dry hole charged with ANFO blasting is assessed while employing a dry hole pumping system to remove water from the drill borehole. Additional standard blasting is also utilized to compare the blasting performances of the two methods. The least-squares linear regression method is adopted to analyze the blasting vibration velocity quantitatively using the measured vibration velocity for each blasting method and the vibration velocity model as a function of the scaled distance. The results show that the dry hole charged with ANFO blasting will lead to greater damping of the blasting vibration, more energy dissipation to crush the surrounding rock, and closer distances for the allowable velocity of the blasting vibration. Also, standard blasting shows much longer influencing distances and a wider range of the blasting pattern. The pilot test confirms the blasting efficiency of dry hole charged with ANFO blasting.

• Explosives and Blasting
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• v.31 no.2
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• pp.32-39
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• 2013

Generally, The way of long hole blasting is carried out in coal-face, basic excavation for dam, mine etc. Recently, this long hole blasting has been implemented in civil engineering for efficiency & economic feasibility. National express no.600 of Pusan outer high-express ${\bigcirc}$ construction site with four lanes of the length of 8km was also a site applied by long hole blasting. But After blasting, tunnel advance rate is less than 75%. As a result of that, Follow-up working time is influenced. Thereby, The total of working process is significantly so increased that planned excavation cannot be implemented many times. For not only improve excavation rate but reduce working process time in job site, we introduce blasting case which apply the ${\phi}36mm$ explosive suited for high desity of charging among long hole blasting in order to overcome mentioned problem.

• Explosives and Blasting
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• v.20 no.3
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• pp.59-71
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• 2002

The points of this design case are the planning and excavation method of a new double-tracked railroad tunnel which is approx. 11∼22 meters apart from existing single-tracked railroad tunnel. For the optimum excavation method some needs are required in design stage, such as the reduction of noise and vibration, public resentment, damage of buildings and construction costs. Hence the estimation and application of allowable noise and vibration criterion is important. The ground coefficient (K, n) of this site is determined by field trial blasting. The excavation method is chosen to satisfy the allowable noise and vibration criterion. In addition, in order to ensure the stability of existing single-tracked railroad tunnel, the instrumentation of maintenance level is accompanied during the construction stage. As a result of this design condition, central diaphragm excavation with line drilling and pre-large hole boring blasting is applied to the area within 15 meters apart from existing tunnel. And above 15 meters apart, pre-large hole boring blasting is designed.

• Explosives and Blasting
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• v.32 no.2
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• pp.9-15
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• 2014

A number of concrete columns were blasted using TNT to study the propagation characteristics of ground vibration caused by different loading conditions in the blast hole of the columns. For each loading condition, peak particle velocity measured on the ground was analyzed. The regression analysis revealed that the use of square blast hole results in smaller vibration magnitude and faster decaying time than the case with circular blast hole. The analysis also showed that the blasting in the closed hole leads to larger vibration magnitude than the blasting in the hole penetrating the column, whereas the difference in vibration decaying time is negligible.

• 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.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.100-108
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• 2017

Because of urbanization, Industrialization and expansion of transportation network, blasting works are recently increasing in construction field. The blasting work influences environmental effects to residents and the safety of facilities around the working place, so the development of blasting technology is needed to reduce the damage to residents. The blasting mechanism in the hole was studied and tested in the blasting sites by the difference of diameter between explosives and drilling hole, which is named by the decoupling effect. This effect was tested by changing the medium between explosives and hole wall in three working sites(railway, highway and industrial complex). The vibration velocity of blasting was recorded and vibration equations were produced by regression analyses. Finally, the structure separation distance was derived using these equations. The testing results show that the specific gravity of medium is larger, the separation distance is smaller and the duration time of blasting is shorter in case of large specific gravity of medium, so the vibration effect stops more fastly in the water compared with the air.

• Explosives and Blasting
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• v.41 no.4
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• pp.41-50
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• 2023

This study, a vertical double-deck method using an electronic detonator was applied to increase excavation volume and reduce blast pollution. In the double deck method, there is a possibility that blasting efficiency may be reduced if bottom deck blasting is carried out without the free surface being completely formed after upper deck blasting. And for this reason, the blasting efficiency of the double deck method varies depending on the deck delay time. Therefore, in this study, we proposed four deck delay times applying 1 to 5 times the hole delay time. And blasting efficiency was evaluated according to fragmentation analysis. As a result of the fragmentation evaluation, the fragmentation of pattern 4 (deck delay time = hole delay time×5) was the best, but it was confirmed that fragmentation efficiency increased significantly from pattern 3 (deck delay time = hole delay time×3). Accordingly, it is analyzed that when blasting a vertical double deck, the deck delay time must be at least three times the hole delay time to obtain an efficient blasting effect.

• Explosives and Blasting
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• v.41 no.4
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• pp.17-28
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• 2023

Recently, the utilization of underground space for research facilities and resource development has been on the rise, expanding development from shallow to deep underground. The establishment of deep underground spaces necessitates a thorough examination of rock stability under conditions of elevated stress and temperature. In instances of greater depth, the stability is influenced not only by the geological structure and discontinuity of rock but also by the propagation of ground vibrations resulting from earthquakes and rock blasting during excavation, causing stress changes in the underground cavity and impacting rock stability. In terms of blasting engineering, empirical regression models and numerical analysis methods are used to predict ground vibration through statistical regression analysis based on measured data. In this study, single-hole blasting was conducted, and the pressure of the blast hole and observation hole and ground vibration were measured. Based on the experimental results, the blast pressure blasting vibration at a distance, and the response characteristics of the tunnel floor, side walls, and ceiling were analyzed.