• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.3
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• pp.377-396
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• 2019

Explosion after penetration of a warhead in an underground structure generally causes considerable displacement, breakage and extensive damage to the target. Therefore, in order to reduce the damage effect, it is required to design an underground structure protection against penetration. In this study, major factors for improvement of penetration protection performance of reinforced concrete underground structures using applied element method are divided into strength (concrete UCS) and density (concrete thickness, reinforcement layers, reinforcement diameters, reinforcement spacings). Based on these major factors, this study performed numerical analysis of simulation of dynamic response by penetrators under various conditions and analyzed the results. The results of this study are expected to be used as basis materials to improve penetration protection performance of reinforced concrete underground structures.

• Explosives and Blasting
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• v.34 no.4
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• pp.1-9
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• 2016

For underwater steel structure, cut that underwater shaped charge device that combines a spring hose, which is an external device of pressure resistance and flexibility with flexible shaped charge, was invented. As a basic experiment for an optimum condition design, an penetration performance was compared by external device shape. To evaluate the result of an experiment, image analysis was carried out after obtaining the model by using the liquid rubber for the penetrated steel plate. To simulate the penetrating process of shaped charge, the AUTODYN program has been used. As a result of analysis, while the average penetration depth of circular and square shaped external devices were similar, the penetration quality was more uniform in the case of circle. In addition, water infiltration occurred in square case, displacement and strain rate according to the increase of the water pressure were measured high.

• Explosives and Blasting
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• v.36 no.1
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• pp.1-11
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• 2018

In this study, several underwater steel cutting tests and AUTODYN numerical analyses were conducted to evaluate the penetration performance of a shaped charge device. Parameter analyses for the contribution rate were conducted by using the robust design method. The parameters adopted in this study were chamber type, stand-off, and wire setting, each of which had three levels in the analysis. Analysis results showed that the contribution rate was most affected by the stand-off, followed by the chamber type and wire setting. Experiments of underwater steel cutting were conducted at water depth of 25m. As expected, the experiments and numerical simulation showed similar results for underwater steel cutting performance, and thus the feasibility of the shaped charge device for underwater steel cutting at deep water depth was verified.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.02a
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• pp.3-8
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• 2002

본 연구는 트랙터 부착형 자동 토양경도 측정 시스템의 개발에 관한 연구로서, 우리나라 토양조건이나 작업형태에 맞는 에너지 절감형 트랙터 로타리날을 개발하기 위한 전단계 연구로서, 기존에 개발된 로타리날과 개량, 보완되어 개발될 로타리날의 성능을 비교 분석하기 위하여 수동 토양경도 측정기의 부정확성을 개량하여 측정의 정확성을 통한 동일 실험조건에서의 실험을 실시하고자 자동으로 작동되며 토양경도측정을 할 수 있는 트랙터 부착형 자동 토양경도 측정 시스템을 개발하는데 목적이 있으며, 그 구체적인 연구 결과는 다음과 같다. (1) 시스템은 토양경도 측정부, 측정장치 구동부, 그리고 트랙터와의 연결부로 구성되었다. (2) 시스템 작동에 필요한 전원공급을 트랙터 배터리에서 공급하였다. (3) 토양경도 측정시 토양속에 돌이나 이물질 층이 형성되어 있는 경우에 콘 페니트로메타가 관입하다가 큰 관입저항 때문에 관입저항 한계설정치까지 가기전 더이상 관입을 못하는 경우가 발생하였다. (5) 성능실험시 관입심이 깊을수록 시험포장 전체에서 대체적으로 토양경도가 높은 것으로 나타났으며, 토양속의 돌이나 이물질 등에의해 경도가 급격히 증가하는 부분이 있는 것으로 사료된다. 이상의 결과에서 살펴보면 본 시스템은 토양경도 측정에 적절하다고 사료된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2359-2368
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• 2013

Cone penetration tests (CPTs) have been increasingly used for site characterizations. However, the site investigations using CPTs are often limited due to soil conditions depending on the cone size and capacity of the CPT system. The small sectional area of a miniature cone improves the applicability of the CPT system due to the increased capacity of the CPT system. A continuous intrusion system using a coiled rod allows fast and cost effective site investigation. In this study, the performance of the continuous intrusion miniature cone penetration test (CIMCPT) system has been evaluated by comparison tests with the standard CPT system at several construction sites in Korea. The results show that the CIMCPT system has a same performance with the CPT system and has advantages on the mobility and applicability. According to field verification tests for scale effect evaluation, the cone tip resistance evaluated by CIMCPT overestimates by 10% comparing to standard CPTs. A crawler mounted with the CIMCPT system has been implemented to improve accessibility to soft ground, and has shown improvement over the truck type CIMCPT system. Therefore, the improved CIMCPT system can be utilized as a cost effective and highly reliable soil investigation methodology to detect the depth of soft ground and to evaluate soil classification.

• Journal of the Korean GEO-environmental Society
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• v.15 no.6
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• pp.75-83
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• 2014

Suction bucket foundation is installed with the differential pressure created by pumping water out of bucket. Bucket foundation has usually been utilized in mooring anchor for offshore platform or floating oil and gas production facilities in the open sea. After suction bucket foundation successfully was applied as the foundation for offshore wind turbines in Europe, it recently attracts much attention in Korea, too. To estimate the penetration resistance of the suction bucket foundation is one of the important matters that should be considered during its installation. This study carried out a series of model tests to investigate the penetration resistance of suction bucket foundation. And the mobilized soil strength factor was reviewed through comparing the experimental results by two installation ways (e.g., push-in-load and suction) and the results calculated by the conventional equation.

• Journal of the Korean Geotechnical Society
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• v.38 no.11
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• pp.97-106
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• 2022

The domestic auger-drilled pile method generally manages the driving penetration (set) value with the final stage of construction. The penetration value has been estimated by manual measurement for a long time. The automation technology is yet to be applied due to workability and high-cost limitations, despite safety issues and lack of reliability in measured results. In this study, a non-contact pile penetration measurement device was developed. Further, the field performance was verified by comparing the measurements with a conventional automation device. In addition, the on-site field quality control method was analyzed using the penetration measuring device. The field experiments confirmed that more reliable bearing capacity estimation could calculate the dynamic damping coefficient and the modified Hiley formula with the developed device. Furthermore, it can be used for pile construction management from the bearing capacity viewpoint, even for piles not subjected to dynamic load tests. 

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.2
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• pp.161-167
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• 2016

In this study, the effect of wall curvature and post-tension force on impact resistance is evaluated by numerical analysis method. A total of twelve cases with two parameters such as wall shape of flat and curved, and consideration of post-tensioning force were included in this study. A 3D detailed finite element model of commercial passenger plane engine is utilized as projectile. The depths of penetration and central displacement calculated from the numerical simulations were compared and analysed. As the results of the numerical simulations of this study, penetration depth was reduced approximately 60~80% due to the application of post-tension force, but the decrease of maximum central displacement was not remarkable. Also, the effect of curvature was relatively insignificant.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.4
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• pp.1-10
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• 2008

Shear wave velocity($V_S$), which can be obtained using various seismic tests, has been emphasized as representative geotechnical dynamic characteristic mainly for seismic design and seismic performance evaluation in the engineering field. For the application of conventional geotechnical site investigation techniques to geotechnical earthquake engineering, standard penetration tests(SPT) and piezocone penetration tests(CPTu) together with a variety of borehole seismic tests were performed at many sites in Korea. Through statistical modeling of the in-situ testing data, in this study, the correlations between $V_S$ and geotechnical in-situ penetrating data such as blow counts(N value) from SPT and piezocone penetrating data such as tip resistance ($q_t$), sleevefriction($f_s$), and pore pressure ratio($B_q$) were deduced and were suggested as an empirical method to determine $V_S$. Despite the incompatible strain levels of the conventional geotechnical penetration tests and the borehole seismic tests, it is shown that the suggested correlations in this study are applicable to the preliminary estimation of $V_S$ for Korean soil layers.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.4C
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• pp.149-157
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• 2012

In order to investigate the soil disturbance induced by anchor-shoe for PVD installation and the anchoring mechanism, a new two dimensional testing system was developed. By using the developed testing system, 1g and centrifuge model tests were performed, simulating the driving-retrieval process of both conventional symmetric anchor shoe and new asymmetric anchor shoe. Various size anchor-shoes were simulated and the results were compared. The images recorded during the installation were analyzed by image processing technique. The results of the image analysis presented the clay disturbance depending on the size and type of anchor shoe. In addition, from the retrieval process, the anchoring mechanism was revealed and the holding capacity was measured. As results, the size of anchor shoe influences the soil disturbance and holding capacity. The new asymmetric anchor shoe reduces the soil disturbance and improves anchoring performance.