• Explosives and Blasting
• /
• v.33 no.1
• /
• pp.13-20
• /
• 2015

Recently, as the demand for development and utilization of underground space is increasing worldwide, the blast damaged zone has become a major issue in constructing underground structures. In this study, numerical analyses were performed for modelling a small-scale blasting of rock plates using PFC3D and ANSYS LS-DYNA. In order to verify the analysis results, several test blasts were conducted. It is concluded from the study that the numerical modelling methods well simulate the crack propagation procedure near blast holes under given conditions.

• Explosives and Blasting
• /
• v.25 no.2
• /
• pp.1-10
• /
• 2007

In this paper, the 1/5 scale models of the reinforced concrete colunms were designed and fabricated. The influence of the number of blasting holes on the exposed length of steel bars and vertical load was investigated. The relation between the length of steel bar and the number of blasting holes was examined by performing the blast tests considering the vertical load on the scaled reinforced concrete columns. Weight of scaled column models by blasting and that of exposed was compared with the number of blasting holes. Finally, based on the exposed length of steel bars and vertical load, the number of blasting holes were calculated. Results shows that the number of blasting holes calculated in this study are suitable for scaled structure models test by blasting demolition.

• Explosives and Blasting
• /
• v.33 no.4
• /
• pp.7-13
• /
• 2015

Recently, as the demand for development and utilization of underground space is increasing worldwide, the blast damaged zone has become a major issue in constructing underground structures. In this study, to verify the explosion modelling method for blast-damaged zone (BDZ) around underground cavern, a series of small-scale test blasts was conducted using the concept of momentum trap. According to the test results, the input parameters to the numerical model (ANSYS LS-DYNA) were corrected. It is concluded that the suggested method of miniature blasting and numerical modelling using the MT concept well simulates the velocity of the MT projectile under given conditions.

• Explosives and Blasting
• /
• v.22 no.4
• /
• pp.1-6
• /
• 2004

In this study, dimension and scale factor of explosives were calculated. Proper dimension and scale factor were considered. Scale factor of 1/256 was obtained when scaled factor of the length was l/4. This value is similar to the ratio of explosives of model test and demolition structure. It seemed that scale factor of length should be larger than 1/4.

• Explosives and Blasting
• /
• v.25 no.1
• /
• pp.53-65
• /
• 2007

When doing a blasting demolition on RC structures made of scale models, scale model members considering both a proper scale factor and mechanical characteristics of materials have to be similar to prototype RC members to analyze the collapse behavior of RC structures. In this study. a similitude law considering the density of prototype materials is calculated. Both mix of concrete and arrangement of reinforcement have been described referring to Concrete Standard Specification as well as Design Standard of Concrete Structure. The scale factor on scaled concrete models considering maximum size of coarse aggregate is about one-fifth of a cross section of prototype concrete members. A scale factor on staled steel bar models is about one-fifth of a nominal diameter of prototype steel bar. According to the mechanical test results of scale models, it can be concluded that the modified similitude law may be similar to compressive strength of prototype concrete and yield strength of prototype steel bar.

• Tunnel and Underground Space
• /
• v.21 no.2
• /
• pp.103-108
• /
• 2011

Along with series of concrete block experiments, a demolition experiment was conducted for a scaled concrete box girder bridge to investigate collapse and blast behavior. Tri nitro toluene (TNT), the standard explosive for strength was adopted as concussion charge. The result show that demolition was caused by not only direct detonation pressures at charging spots but also blast pressures at inner wall of concrete box girder.

• Explosives and Blasting
• /
• v.20 no.3
• /
• pp.97-109
• /
• 2002

본 연구에서는 콘크리트 기둥 발파시 단부 조건을 고려하여 수직 하중에 따른 발파에 의한 파쇄형태를 비교하였다. 또한 파쇄도에 대한 정량적인 해석을 위해 상·하단부의 무게비와 각 방향별 단면의 면적비를 비교하였으며, 장전층을 달리한 모형 구조물 발파해 체시 각 층별 기둥의 파쇄형태와 방향별 면적비를 비교하여, 전체적인 구조물의 파쇄도를 비교하였다.

• Explosives and Blasting
• /
• v.22 no.1
• /
• pp.33-43
• /
• 2004

In this study, a comparison was made between the resulting behaviors of scaled model test and particle flow analysis for blasting demolition of a reinforced concrete structure. For the test and analysis, a progressive failure of a five-story structure was considered. The dimension analysis was carried out to properly scale down the real structure into the laboratory size. The test model was made of the mixture of gypsum, sand and water along with soldering lead to analogy reinforcing steel bars. The ratio of mixing components was chosen to best represent the scaled down strength and deformation modulus. The columns and girders of the structure were precasted in the laboratory and assembled right before the blasting test. The numerical analysis of the blasting demolition was carried out using PFC2D (Particle Flow Analysis 2-Dimension by Itasca). The results of the blasting of concrete lahmen structure showed roughly identical demolition behavior between scaled model test and numerical test. For the blasting of the reinforced concrete structure, the results were more identical and closer to the real demolition behavior, since the demolition behavior was better represented in this case due to the increased tensile strength of the component.

• Proceedings of the KSEE Conference
• /
• 2007.10a
• /
• pp.53-59
• /
• 2007

• Computational Structural Engineering
• /
• v.8 no.1
• /
• pp.30-38
• /
• 1995

이방향 천공 발파공법의 실용성을 입증하여 실시공에 착수하기 위해서는 수치해석을 통하여 사전에 종방향 및 방사방향 천공발파에 따른 지표면에서의 지반진동의 영향을 알아보는 것이 필요하였다. 정확한 현장조건과 발파하중이 주어진 상태에서의 정밀해를 구하기 위해서는 시공상의 발파패턴대로 전체 발파공을 모형화하는 것이 필요하나 앞서 언급한 바와 같이 해석목적상 기존공법과 신공법의 지반응답의 차이를 비교하는 것이 주목적이였기 때문에 해석조건을 동일하게 가정하고 발파공도 대표적인 방향성을 가지는 1개공만을 선택하여 해석을 수행하였다. 기존 종방향 천공 발파공법과 신공법인 이방향 천공 발파공법의 상대적 비교를 위한 3차원 동적 해석결과, 관심의 대상이 되는 터널 직상부의 경우 기존의 종방향 천공 발파에 비해 이방향 천공발파는 진동이 두드러지게 감소함을 알 수 있었으며 이는 발파공의 방향성에 따라 지반응답이 크게 영향을 받는다는 것을 의미한다. 따라서 터널굴착시 문제시 되는 지상구조물의 위치에 따라 발파공의 위치를 적절히 조절함으로써 문제발생 예상지역의 진동치를 감소시킬 수 있을 것이라 판단된다. 그러나 이러한 잇점은 확대발파전 파이롯트 터널이라는 자유공간이 존재할 때만 가능하므로 이방향 천공 발파공법은 TBM의 효용성을 극대화시킨 것이라 할 수 있다.