• Journal of the Korean Professional Engineers Association
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• v.44 no.1
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• pp.44-47
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• 2011

Huge amount of energy produced by an underground nuclear test is released into the surrounding rock. Depending on the properties of the bed rock surrounding the detonation and overlaying it a variety of effects can occur. At some particular depth the increasing amount of material thrown upward is exactly balanced by the decreasing fraction escaping the crater, the crater volume reaches to a maximum. This depth is called the optimum depth of burial and varies somewhat with the geology of the site, being greater for less dense and structurally weaker material.

• The Journal of Engineering Geology
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• v.19 no.1
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• pp.1-8
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• 2009

Geophysical surveys were conducted on an upper part of a natural slope located at Daejeon University. Electrical resistivity and seismic refraction measurements were carried out to obtain information on a weathered zone and internal structure at shallow depth, while AMT measurement a bed rock and geological structure at deep depth. With all the techniques applied, these results show a good correlation between electrical resistivity images and refraction velocity distributions for the characterization of a weathering and geological structure at depth. In particular, AMT survey seems to be the powerful tool for detecting a distribution of a bed rock with deep depth. The combined geophysical investigation produced a detailed image of a subsurface structure and improved well in the interpretation.

• Tunnel and Underground Space
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• v.28 no.3
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• pp.232-246
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• 2018

In this study, the relationship between in situ seismic wave velocities and RMR (rock mass rating) was investigated in a test bed for the examination of the basis of rock classification (RMR) based on seismic wave velocity. The seismic wave velocity showed a monotonous increase with depth. It was also found that there was no systematic correlation between the seismic wave velocity (Vp) and other parameters (RQD, joint spacing, UCS, rock core Vp, and RMR) collected at the same depth of the same borehole. However, correlative relation was observed among RMR, RQD, and joint spacing. On the other hand, when all the data in the borehole (three holes) are examined without considering the depth, Vp still shows no correlation with RMR parameters (e.g., correlative coefficient for uniaxial compressive strength and joint spacing are 0.039 and 0.091, respectively), but Vp shows weak correlative relation with RMR and RQD (correlative coefficient for RQD and RMR are 0.193 and 0.211, respectively). Thus, it is found that it is difficult to deduce physical properties of rock mass directly from seismic wave velocities, but the seismic wave velocity can be used as a tool to approximate rock mass properties because of weaker correlation between Vp and RMR with RQD. In addition, the velocity value of for soft and moderate rocks suggested by widely used construction standards is slower than that of the observed velocity, implying that the standards need to be examined and revised.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.221-228
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• 2005

The economic growth brought the demand of bridge connected to island and land increasingly in Korea. Therefore, Civil engineer has faced a lot of problem to be considered such as structural stability, economic feasibility and constructional method. At the bridge site to be constructed, the depth of water is about 24m, the thickness of weathered rock overlaying bed rock is thicker than 36m. If open caisson foundation is supported in bed rock, the hight of foundation is about 60m. It is difficult to construct in these conditions. If open caisson foundation is supported in weathered rock, the size of the foundation should be increased. And If we apply the pile foundation, the higher construction cost will be needed. Under the circumstances, we need a new foundation type-composite foundation that is consisted of open caisson and cast-in-place piles. Because the design concept of composite foundation is not presented in Korea Bridge Design Standard, we are willing to clear the bearing behavior of composite foundation by numerical analysis in this paper.

• Journal of the Korean Institute of Landscape Architecture
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• v.15 no.1
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• pp.9-16
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• 1987

In Seoul metropolitan area, rockily denuded fores lands are widely distributed. Out of the rock-exposed hillslopes, Kwanak-Samsung mountains and Bookhan-Dobong mountains areas are the most severely eroded land at present To develope the rehabilitation measures for the rock-exposed hillslopes, it is essentially required that mechanisms of rock debris production and movement from the rock-exposed hillslopes should be studied. And also, suitable experiments for planting techniques should be practised at the field level. In this context, some experiments for the on-site fixation of the unstable stone-debris including plantation establishments on the rock-exposed hillslopes, have been carried out for 4 years from 1983 to 1986 at Kwanak mountain hillslopes. The results may be summarized as follows : 1) The soil environment-tolerable tree species for plantation extablishment on rock-exposed hillslopes include Buxus microphylla var. koreana, Forsythia koreana, Juniperus chinensis var. sargentii, Alnus hirsuta and Pinus rigida. These trees have, however, been showed fairly good growth performence at the places having more than about 30cm of soul layer depth above rock-bed. 2) In raising of seedlings to plant on the rock-exposed hillslopes, containerized seedling practices knave been appeared as the most adoptable measures. 3) In fixation of the unstable stole debris-and-sands on the on-site of rock. exposed hillslopes, the stone-lined barrier measures are more effective at comparatively large-sized places of rock-exposed hillslopes while the stone-bowed barrier measures are more effective at small-sifted isolated sold-debris places. The stone-buttressed terraces measures are more effective at the soil-composed hillslopes rather than rock-exposed hillslopes.

• Tunnel and Underground Space
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• v.17 no.1 s.66
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• pp.1-8
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• 2007

In Norway, about 30 subsea tunnels have been constructed over the last 20 years. The minimum depth of 17 subsea tunnels is 56 m and rock cover are between 23 and 49 m. As the project areas for subsea tunnel are covered by water, special investigation techniques need to be applied and the investigation results are more uncertain than that of most conventional tunnel projects. The indefinite potential of water inflow and the salinic character of ingress water represent considerable problems for tunnel equipment and rock support materials. The least stable conditions are represented by major faults or weakness zones containing heavily crushed rock and clay gouge. This paper introduces the Oslofjord subsea tunnel project including minimum rock cover requirement, risk of water inflow, investigation costs, construction costs, and traffic & operation costs.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.287-292
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• 1998

The phenomena of local scour due to a current from a seadike closure gap which is protected by rock, then on to an erodible bed, have been studied. Based on the data of hydraulic model test, the scour characteristics have been investigated for the variation of maximum scour depth with time until reaching equilibrium stage and the shape of ultimate scour hole. A brief evaluation of DHL formula for the relationship between maximum scouring depth and time and a dimensionless form leading to time-scale introduced. On the basis of DHL formula, modified DHL formula denoted DHL-RDC formula is extend to the range of estimation of scour depth compared to DHL formula verified by model test.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1571-1580
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• 2008

Subsea tunnels that link land to island and among nations for transportation, efficient development of limited surface and pursuit of economic development should be designed to support pore water pressure on the lining. It is generally constructed in the bed rock of the sea bottom. When the tunnel excavation face meets fractured-zones below sea bottom, collapse may occur due to an increase of pore water pressure and large inflow. Such an example can be found in the Norwegian subsea tunnel experiences in 1980's. In this study hydraulic behavior of tunnel heading is investigated using numerical method based on the collapse of Norwegian subsea tunnel. The effect of pore water pressure and inflow rate were mainly concerned. Horse-shoe shaped model tunnel which has 50 m depth from the sea bottom is considered. To evaluate hydraulic performance, parametric study was carried out for varying relative permeability. It is revealed that pore water pressure has increased with an increase of sea depth. Especially, at the fractured-zone, pore water pressure on the lining has increased significantly. Inflow rate into tunnel has also increased correspondingly with an increase in sea depth. S-shaped characteristic relation between relative permeability and normalized pore water pressure was obtained.

• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.111-122
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• 2005

The data on the pile load tests performed on 35 large drilled shafts are analyzed to investigate the load-settlement characteristics of large drilled shafts embedded in bed rocks. Generally, the settlement of large drilled shafts embedded in bed rocks is too small to determine the ultimated load with application of the regulation in design code for either the total settlement or the residual settlement. Therefore, to determine the yield load of large drilled shafts embedded in bed rocks, p(load)-logS (settlement) curve method, which has been proposed originally for the driven pile, was applied to the investigation on the data of the pile load tests. This technique shows that the yield load can be determined accurately and easily rather than other conventional techniques such as P-S, logp-logS, S-logt, and P-S curve methods. An empirical equation is proposed to represent the relationship between pile load and settlement before the yield loading condition. And the settlement of piles was related with the depth embedded in rock as well as rock properties. Based on the investigation on the data of pile load tests, the resonable regulations f3r both the total settlement and the residual settlement are proposed to determine the yield load of large drilled shafts embedded in bed rocks.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.98-107
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• 2000

Free-field ground motion during earthquake is significantly affected by the local site conditions and it is essential for the seismic design to perform the ground response analysis In this study, ground response analyses based on the equivalent linear method were carried out to evaluate the effects of various ground conditions on the site amplification. Four major factors including the depth of the site(very soft and dense soil), the impedance ratio between soil layer and bed rock, linear analysis versus equivalent linear analysis, and the location of soft soil layer were deeply discussed. Based on the analysis results, the importance of various local site conditions on the site amplification was emphasized.