• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.5
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• pp.469-485
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• 2016

The failure of rock mass around deep tunnel, different from shallow tunnel largely affected by discontinuities, is dominated by magnitudes and directions of stresses, and the failures dominated by stresses can be divided into ductile and brittle features according to the conditions of stresses and the characteristics of rock mass. It is important to know the range and the depth of the V-shaped notch type failure resulted from the brittle failure, such as spalling, slabbing and rock burst, because they are the main factors for the design of excavation and support of deep tunnels. The main features of brittle failure are that it consists of cohesion loss and friction mobilization according to the stress condition, and is progressive. In this paper, a three-dimensional numerical model has been developed in order to simulate the brittle behavior of rock mass around deep tunnel by introducing the bi-linear failure envelope cut off, elastic-elastoplastic coupling and gradual spread of elastoplastic regions. By performing a series of numerical analyses, it is shown that the depths of failure estimated by this model coincide with an empirical relation from a case study.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.903-906
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• 2001

The objective of this experimental study was to understand the effect of horizontal shear bar on the shear behavior of R.C. deep beams. Therefore, in the test program, the horizontal shear bar ratio($\rho_{sh}$) and shear span-to-overall depth ratio(a/h) are considered as two main variables. Test results indicate that for deep beams with a/h equal to 1.0, horizontal shear bar is less efficient in restricting the diagonal crack width development and enhancing the ultimate shear strength. So, it can be concluded that shear resistance of horizontal shear bar is related to a/h rather than clear span-to-effective depth ratio($l_{n}$/d) recommended in ACI code.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.162-167
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• 2000

The warm deep drawability in square cup drawing is investigated about a newly developed high-strength steel sheet with retained austenite which is transformed into martensite during forming. For this investigation, six steps of temperature ranges, from room temperature to $250^{\circ}C$, and five kinds of drawing ratio, from 2.2 to 2.6 were adopted. As a result the maximum drawing force and the maximum drawing depth were affected by the elevated temperatures, and the more stable thickness strain distribution was observed to the elevated temperatures. But blue shortness happened over $200^{\circ}C$. The FEM analysis using the LS-DYNA code is adopted to compare the experimental results with the analytical results for thickness strain distribution.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1155-1158
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• 2006

This paper presents a study on the construction condition and environmental effect of deep soil mixing. Construction condition means the difference in unconfined compressive strength with respect to the depth and location of samples. Environmental effect means alkalinity diffused from soil stabilizer. The experimental results indicate that the unconfined compressive strength vary with respect to the depth, and doesn't show consistency pattern. So, in field application we must decide a mixing ratio enough to satisfy the least unconfined compressive strength. The difference in unconfined compressive strength with respect to the location of samples is negligible. The generation of alkalinity from soil stabilizer is reduced by permeating in non-improved soil and it is expected that the diffusion of alkalinity has no environmental effect on soil and ground water.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.537-544
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• 2005

We find out many soft ground deep excavation cases where results of careless overexcavation accelerate the advance of loosening zone of adjacent ground, bucklings of struts and bottom heaves happen due to delayed supporting time. This article introduces a soft ground deep excavation case where steel pipe sheet piles were used with struts as an earth retaining system. There were 2 times of buckling in the supporting system and heaving of bottom ground due to overexcavation and insufficient penetration depth of the steel pipe sheet piles. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

• Journal of Mechanical Science and Technology
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• v.15 no.7
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• pp.839-846
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• 2001

Some deep drawing characteristics at elevated temperatures were investigated for the SCPI steel sheets by using a Cr-coated die. For this investigation, six different temperatures between room temperature and 250$\^{C}$, and six different drawing ratios ranging from 2.4 to 2.9 were considered. As a result, the limiting drawing ratio, the maximum drawing force and the maximum drawing depth were found to be affected sensitively by temperature, and more stable through-thickness strain distribution was observed at elevated temperatures. Some experimental results compared favorably with theoretical results obtained by using the finite element method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.63-70
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• 1999

Some deep drawing characteristics to the elevated temperatures were investigated for the SCP1 steel sheets by using the Cr-coated die. For this investigations six steps of temperature ranges from room temperature to 25$0^{\circ}C$ and six kinds of drawing ratio from 2.4 to 2.9 were adopted. As a result the limiting drawing ration maximum drawing force and the maximum drawing depth were sensitively affected by the elevated temperatures and the more stable thickness strain distribution was observed to the elevated temperatures, Some experimental results were compared with analytical results using the DYNA-3D code.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.319-321
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• 2007

This paper introduces a general overview of the 6000m class deep-sea ROV. Hemire and Henuvy. and then describes its motion control system. It is developed by Korea Ocean Research & Development Institute(KORDI) for 6 years since 2001. sponsored by the Ministry of Maritime Affairs and, Fisheries (MOMAF). Hemire is remotely operated by a fiber optic telemetry. where 6 thrusters are controlled by operator in manual mode and by auto depth control and auto heading control in auto mode. In this paper. operational mechanism of manual and automatic mode with some convenient functions for operator is desc.ribed. Finally, results of sea trial conducted at the Philippine sea where a depth is 5.770m are shown.

• Transactions of Materials Processing
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• v.8 no.3
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• pp.221-221
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• 1999

Warm deep drawability in a square cup drawing was investigated using a newly developed high-strength steel sheet with retained austenite that was transformed into martensite during formation. For this investigation, six different temperatures between room temperature and 250℃, and five different drawing ratios ranging from 2.2 to 2.6 were considered. The results showed that the maximum drawing force and the drawing depth were affected by the change in temperature, and a more stable thickness strain distribution was observed at elevated temperatures. However, blue shortness occurred at over 200℃. FEM analysis using the LS-DYNA code was used to compare the experimental results with the numerical results for the thickness strain distribution.

• Transactions of Materials Processing
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• v.9 no.2
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• pp.186-192
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• 2000

Some deep drawing characteristics to the elevated temperatures were investigated for the SCPI steel sheets by using the Cr-coated die. For this investigations, six steps of temperature ranges, from room temperature to 25$0^{\circ}C$, and six kinds of drawing ratio, from 2.4 to 2.9 were adopted. As a result, the limiting drawing ratio, maximum drawing force, and the maximum drawing depth were sensitively affected by the elevated temperatures, and the more stable thickness strain distribution was observed to the elevated temperatures. Some experimental results were compared with analytical results using the DYNA-3D code.