• Tunnel and Underground Space
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• v.24 no.1
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• pp.97-109
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• 2014

In order to identify the characteristics of the propagation depending on delay time (20, 25 ms) and priming location (top priming, middle priming, bottom priming), test blasts were carried out a total of 4 times using different spacing, burden, drilling length, charge per delay and was derived the formula to predict blast vibration. This study investigated the characteristics of vibration by analysis of the nomogram and prediction of Peak Particle Velocity (PPV) from delay time and priming location by the formula to predict ground vibration. And it analyzed the trends of vibration increase by standards charge 0.5, 1.6, 5, 15 kg. Standards charge is "Blasting design and construction guidelines to road construction" by the Ministry of Land, Infrastructure and Transport. Depending on the charge in favor of vibration control method is proposed. Thus, when the design was to be used as a variable.

• 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.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.1 s.24
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• pp.39-46
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• 2007

The blasting load induced by the explosion of the powder generation the vibration of the ground and affects on nearby ground and underground structures. The structures are possibly damaged and it may create the social problems such as noneconomic construction due to the delay of the construction period especially in urban areas. Therefore, the stability of the nearby structures need to be evaluated. In this study, the stability of the tunnel is estimated and examined by the analytical solution and by using $FLAC^{2D}$ which is one of the programs based on the finite difference analysis.

• Membrane Journal
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• v.14 no.2
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• pp.142-148
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• 2004

This paper presents the enhancement of oxygen transfer efficiency using vibrating intravascular lung assist device (VIVLAD) for patients having chronic respiratory problems. The flow rate was controlled by the pump and monitored by a built-in flow meter. The vibration apparatus was composed of a piezo-actuator, a function generator, and a power amplifier. Gas flow rates of up to 6 L/min through the 120-cm-long hollow fibers have been achieved by exciting a piezo-actuator. The output PVDF sensor and FRF (frequency response function) were investigated by various frequency in VIVLAD. As a result, the maximum oxygen transfer rate was found to occur with maximum amplitude and the transfer of vibration to the hollow fiber membranes. It was excited by the frequency band of 35 Hz at various distilled water flow rates, and various module types.

• Explosives and Blasting
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• v.33 no.2
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• pp.15-24
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• 2015

In general, blast vibrations could make underground cavern unstable by causing relative movements between the surrounding rock blocks that are divided by discontinuities such as joints and faults around the cavern. In the study, a blast guideline was established to obtain the stability of a large-scale cavern for underground crusher room in an open pit limestone mine in Korea. The guideline was suggested in the form of a standard calculation method of the maximum charge per delay for a safe blast. The allowable level of peak particle velocity for the cavern was determined based on the result of a numerical analysis using FLAC2D. The ground vibration data required for the study was obtained from field measurements.

• Computational Structural Engineering
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• v.1 no.1
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• pp.123-133
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• 1988

A method to calculate maximum dynamic deflection, which is close to the measured deflection, was proposed by comparing the real deflection with the claculated one in three span continuous highway steel bridge. From this, the pattern of variation of impact factors depending an vehicle speeds and weights was studied in simple and continuous bridges. From the numerical analysis, it was known that the maximum dynamic deflection which is close to the measured one could be obtained by using the transformed flexural rigidity of a bridge, and the factors are generally increased with increasing vehicle speed. However, it was thought that there are some problems in the code specification about the impact factors of the continuous bridges.

• Composites Research
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• v.34 no.6
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• pp.380-386
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• 2021

This paper aims to improve the critical speed of power-take-off (PTO) shafts by using carbon fiber reinforced plastics (CFRPs). The PTO shaft was designed with titanium-CFRPs hybrid structure in order to compensate the low shear strength of CFRPs. Based on the requirements for PTO shafts, the dimensions of PTO shafts were determined through a parametric study. To evaluate the performance of the PTO shaft, a vibration test, a static torsion test, and a torsion durability test were performed. In the vibration test, the critical speed of PTO shafts was 20570 rpm, which was 7.5% higher than that of titanium shafts. Additionally, it was confirmed that the maximum allowable torque of the PTO shaft was 2300 N·m. Finally, under repeated load in the range of 11.3 to 113 N·m, the fatigue failure in the PTO shaft did not occur up to 10⁶ cycles.

• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.71-86
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• 2023

Rock blasting tests using underground penetration-type displacement sensors were conducted, and three-dimensional finite element numerical analyses were performed to assess their applicability and mitigate slope hazards during rock blasting. Additionally, parameters influencing vibration velocity were investigated during the tests. The results confirmed that underground penetration-type displacement sensors are suitable for monitoring rock slope behavior, and the numerical analyses revealed that the most influential parameter on vibration velocity during rock blasting is the unit weight. Furthermore, it was observed that vibration velocity decreases significantly with distance from the blast source, and proximity to the source leads to substantial variations in vibration velocity due to differences in elastic modulus and unit weight. Changes in internal friction angle and adhesive strength had minimal impact.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.461-468
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• 2001

지진등에 의해 유발된 동 하중에 의한 지반-구조물 계의 응답은 지반-구조물사이의 경계에서의 마찰특성과 미끄러짐에 의해 크게 영향을 받게 된다 본 논문에서는 진동대(Shaking table)를 이용하여 조립토와 건설재료(Steel)의 경계에서 지반으로부터 지중구조물에 전달되는 전단응력 의 전달정도를 파악하기 위한 실험을 실시하였다. 본 실험에서 설정한 미끌어짐속도 범위내에서는 미끄러짐속도 변화에 따른 조립토와 건설재료(Steel)사이의 동마찰계수의 변화가 작다는 사실이 관찰되었다. 그리고 조립토의 평균유효입경의 변화가 동마찰계수에 미치는 영향도 함께 조사되었다. 또한 이 동마찰계수를 같은 조립토에 대한 평면변형률시험을 통해 얻어진 최대내부마찰각으로부터 구한 마찰계수와 비교하여 정량화하였다.

• Explosives and Blasting
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• v.33 no.3
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• pp.29-50
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• 2015

Safe blast criteria based on the concept of scaled distances can be obtained from the statistical analysis on measured peak particle velocity data of blast vibrations. Two types of scaled distance widely used in Korea are the square root scaled distance (SRSD) and cube root scaled distance (CRSD). In contrast to SRSD scheme, however, the function of maximum charge per delay for CRSD increases without bound after the intersection point of these two functions despite of the similar goodness of fits. To prevent structural damage that may be caused by the excessive charge in the case of CRSD, it is suggested that CRSD be used within a specified distance slightly beyond the intersection point. On the other hand, there are several attempts that predict vibration level(VL) from the peak particle velocity(PPV) or estimate VL based on the scaled distances without considering their frequency spectra. It appears that these attempts are conducted in blasting contracts only for the purpose of satisfying the environment-related law, which mainly deals with the annoyance aspects of noises and vibrations in human life. But, in principle there could no correlation between peaks of velocity and acceleration over entire frequency spectrum. Therefore, such correlations or estimations should be conducted only between the waves with the same or very similar frequency spectra. Finally, it is a known fact that structural damage due to ground vibration is related to PPV level, the safety level criteria for structures should be defined by allowable PPV levels together with their zero crossing frequencies (ZCF).