• Journal of the Korean Geotechnical Society
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• v.17 no.1
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• pp.109-118
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• 2001

대구지역은 광범위한 층리가 균일한 형태로 발견되는 지역으로 역학적인 이방성을 나타내고 있다. 이러한 이방성을 가진 지반은 지하 구조물의 거동이 등방과 다른 양상을 보이므로 이방성해석이 수행되어야 한다. 이에 본 연구에서 대구지역 셰일에 대해 암판정상 경암과 보통암에 대해 동일한 시료에서 등방과 이방상태의 탄성정수를 층리각도($\beta$)별로 산출하였고 이것을 바탕으로 하여 유한 요소법을 사용한 이방성 해석을 수행하였다. 해석결과 이방상태의 응력과 변위의 결과는 등방과 다름을 알 수 있었다. 변위는 층리각에 따라 등방에 비해 지표면에서 약 3배까지 증가하며, 록볼트는 최대 2.04배, 숏크리트는 2.93배 증가하게 나타난다. 또한, 측압계수(K$_{0}$)가 이방성 암반과 터널구조물에 미치는 영향을 알 수 있었다. 따라서, 본 지역과 같은 층리가 존재하는 지반의 구조물 건설에서 이방성해석이 필수적임을 알 수 있다.

• Korean Journal of Environment and Ecology
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• v.11 no.4
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• pp.480-485
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• 1998

The annual increasing rate of visitors was 3 percent in Soraksan National Park form 1990 to 1997. Secenty nine percent of total visitors in Soraksan National Park has visited Oysorak district due to convenient access and facilities. Approximately, 6~17 percent of visitors passing through Sorakdong ticket office at Oysorak district has climbed up Taech'ongbong(peak), the others have visited Ulsanbawi, Pisondae and Madungnyong close at hand. Climbers from Osekyaksu to Taech'ongbong(peak)were more in autumn than in summer. Visiting pattern in Soraksan National Park showed differences by districts, seasons and days of the week.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.31-37
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• 2011

Understanding of the phase distribution in a multi-phase polycrystalline material is important because it can affect material properties and mechanical behaviors significantly. In this research, probability functions (two-point correlation and lineal-path functions) are used to represent the phase distributions of microstructures. The two-phase microstructures with random phase distribution are reconstructed using probability functions and compared with original samples. Mechanical behaviors of the virtual samples for different directions are evaluated using a finite element method. It is confirmed that microstructures with the same statistical characteristics can be generated using the reconstruction method. It is also demonstrated that the characteristics of the probability functions and mechanical reponses between the original and reconstructed microsturctures are statistically identical.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.5C
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• pp.201-208
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• 2010

In this study, the ground settlement was investigated by using monitoring data of the test sites where vacuum consolidation method and surcharge method were applied for improving deep soft soil. The monitoring data are chosen in ${\bigcirc}{\bigcirc}$ area port construction site reclaimed with very soft dredged clay. These data are analyzed to compare the consolidation characteristics between the different loading methods for soil improvement. Through analysis of the loading time, it is shown that the ground settlement reaches its allowable value under vacuum consolidation loading by about 45% faster than that of the surcharge loading consolidation. This could be explained that vacuum consolidation method makes the isotropic consolidation condition so that the time for reaching a certain final preloading without soil failure can be shortened.

• Journal of the Korean Geotechnical Society
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• v.26 no.2
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• pp.5-14
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• 2010

In this study, cyclic triaxial tests were performed under anisotropically consolidated condition by using irregular earthquake loading to consider in-situ condition and seismic wave. Jumunjin sand with a relative density 50 percent was used in the tests. The consolidation pressure ratio (K) was changed from 0.5 to 1.0. The Ofunato and Hachinohe wave were applied as irregular earthquake loadings and liquefaction resistance strengths of each specimen were estimated from the excess pore water pressure (EPWP) ratio. As a results of the cyclic triaxial tests, EPWP ratio increased with increased K value. It shows that isotropically consolidated sand is more susceptible to liquefaction than anisotropically consolidated sand under equal confining pressure and dynamic loadings. From the test results, the relationship between K and EPWP ratio normalized by effective confining pressure and deviator stress was proposed. And a new factor which corrects the liquefaction resistance strength for the in-situ stress condition is proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.255-260
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• 1993

The behavior of pure silt was investigated by using an automated triaxial testing device. The stress-strain behavior of silt due to the volume deformation tendency was compared with the behavior of clay prior to failure and behavior at failure under monotonic undrained compression and extension conditions. A pure silica flour was chosen to form samples. The isotropically normally-consolidated samples with 450 kPa of effective mean confining pressure and overconsolidated samples through unloading were tested. Based on the experimental results, it was qualitatively identified that the undrained strength of normally-consolidated silt increases due to its dilatant nature which is not seen in clay. Also the overconsolidated silt shows a significantly different behavior under the monotonic loadings due to the volume deformation tendency.

• Geotechnical Engineering
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• v.9 no.4
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• pp.27-36
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• 1993

The drained and undrained behavior of pure silt was investigated experimentally. Special attention was given to the stress-strain behavior of silt prior to failure and behavior at failure under monotonic and cyclic loading. A pure silica flour was chosen to form samples with two different densities of D,=80%, eo=0.68 and D,=35%, eo=0.9. The isotropically consolidated samples were tested in the triaxial testing device under monotonic undrained, drained compression and extension conditions. Also samples were tested under cyclic undrained condition. Based on the experimental results. it was qualitively identified that the overall behavior of silt is similar to that of sand. When compared with clay, silt shows a significantly different behavior due to its dilatant nature under both the monotonic and cyclic shear loadings.

• Tunnel and Underground Space
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• v.12 no.3
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• pp.220-228
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• 2002

Thermal flow through jointed rock mass was analyzed by numerical methods. The effect of a single set of joints on the heat conduction was analyzed by one-dimensional model and compared with the analytical solution. When a joint is completely dry, the joint behaves as a thermal break inducing jumps in temperature distribution even at steady state. Therefore when joints are completely dry, individual joint has to be taken into consideration to get a good result. When joints are partially or fully saturated, the thermal conductivity of the joints increases drastically and the jumps in temperature distribution become less severe. Therefore the effect of joint in heat conduction can be well absorbed by continuum anisotropic model whose thermal properties represent overall thermal properties of the intact part and the discontinuities. Since the effect of joints becomes less important as the degree of the saturation increases, the overall thermal response of the rock mass also becomes close to isotropic. Therefore it can be concluded that a great effort has to be made to obtain a precise in-situ thermal properties in order to get a good prediction of the thermal response of a jointed rock mass.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.4
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• pp.103-112
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• 1991

In this study, a numerical model was established and applied to simulate the steady-state groundwater and heat flow in an isotropic, heterogeneous, three dimensional aquifer system with uniform thermal properties and no change of state. This model was developed as an aid in screening large groundwater-flow systems as prospects for underground waste storage. Driving forces on the system are external hydrologic conditions of recharge from precipitation and fixed hydraulic head boundaries. Heat flux includes geothermal heat-flow, conduction to the land surface, advection from recharge, and advection to or from fixed-head boundaries. The model uses an iterative procedure that alternately solves the groundwater-flow and heat-flow equations, updating advective flux after solution of the groundwater-flow equation, and updating hydraulic conductivity after solution of the heat-flow equation. Dierect solution is used for each equation. Travel time is determined by particle tracking through the modeled space. Velocities within blocks are linear interpolations of velocities at block faces. Applying this model to the groundwater-flow system located in Jigyung-ri. Songla-myun, Youngil-gun. Kyungsangbuk-do, the groundwater-flow system including distribution of head, temperature and travel time and flow line, is analyzed.

• Geotechnical Engineering
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• v.12 no.5
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• pp.17-26
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• 1996

The undrained behavior of Asan marine soil was investigated by using an automated triaxial testing device. The stress-strain behavior at the preand postfailure state of marine soil under undrained compression and eatension conditions was compared with the behavior of pure silt, pure clay and the overall behavior of Asan marine soil was predicted with the modified Camflay model and the bounding surface model. The marine soil sampled in Asan bay area was clayey silts with 70oA silt-30% clay content and the testing samples were prepared in both undisturbed and remolded conditions. All samples are normally consolidated with 400 kPa of effective mean confining pressure and each sample is unloaded to 200, 100, 67 kPa, respectively. And then the shear test was performed with different confining pressure. According to experimental results, there exists an unique failure line whose slope is lower than silt's and higher than clay's. It is identified that the undrained shear strength of normally consolidated samples increases after crossing the phase transformation line because of volume dilation tendency which is not seen in clay. Overconsolidated samples show different soil behavior compared with pure silt due to its tendency of change in volume. It is also found that the overall behavior of Asan marine soil cannot be predicted precisely with the modified Cam-clay model and the bounding surface model.