• 한국농공학회:학술대회논문집
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• 한국농공학회 2005년도 학술발표논문집
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• pp.361-366
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• 2005

Since most soils exist above the ground water table, negative pore pressure exist in unsaturated soils. Negative pore water pressure in unsaturated soil affects the soil structure and degree of saturation and it is important for accurate evaluation of unsaturate flow and behavior. This negative pore pressure is called a matric suction which causes an increased shear strength. Therefore, it is required that the effect of increase in the shear strength should be included in a geotechnical analysis. From the test result, the influence of net confining pressure and matric suction on the shear strength was analyzed and strength parameter was increased with matric suction increase and a unliner relationship was found to relate matric suction and shear strength.

• 한국지반공학회논문집
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• 제23권10호
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• pp.57-64
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• 2007

현재 불포화토에 대한 많은 연구가 진행되어 왔고 최근 들어 많은 연구자들이 불포화지반의 안정성을 보다 합리적으로 판단하고 해석하기 위해 불포화상태를 고려한 연구의 필요성을 제기하여 왔다. 이를 위해서는 흡인력에 대한 전단강도의 증진효과를 정량화하고 이를 안정해석에 적용하는 것이 요구되고 있는 실정이다. 따라서 본 연구에서는 불포화 사질토의 전단강도 특성을 규명하기 일해서 국내에 널리 분포하는 화강풍화토 7가지를 대상으로 불포화 삼축압축시험을 수행하였으며, 결과치를 분석하여 강도특성을 규명하고자 한다.

• 한국산학기술학회논문지
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• 제10권11호
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• pp.3287-3295
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• 2009

본 연구는 강우재현장치를 제작하고, 화강암질 풍화토로 조성된 모형사면에 강우 및 사면조건에 따라 모형실험과 수치해석을 실시하였다. 모형실험에서 계측된 체적함수비와 간극수압의 변화특성을 분석하였으며 또한 수치해석 결과와 비교하였다. 체적함수비는 강우강도가 크고 사면경사가 급할수록 한계값에 도달하는데 짧은 시간이 소요되는 반면 강우강도가 작고 사면경사가 완만할수록 많은 시간이 소요되는 것으로 나타났다. 강우강도가 작고 강우지속시간이 짧을수록 더 큰 부의 간극수압을 나타내고 회복하는 시간도 짧은 것으로 나타났다. 이와 반면 강우강도가 크고 강우지속시간이 길수록 부의 간극수압을 회복하는데 오랜 시간이 소요되는 것으로 나타났다. 강우재현 모형실험과 수치해석을 수행한 결과 체적함수비와 간극수압의 분포경향이 유사하게 나타났다. 그러나 체적함수비는 최대 5% 정도, 간극수압은 최대 3kPa 정도의 차이를 보였다.

• 농업과학연구
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• 제39권3호
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• pp.427-439
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• 2012

In this study, an experiment with large-scale model was performed according to raising embankment in order to investigate the behaviour of failure due to overtopping. The pore water pressure, earth pressure and settlement by high water level, a rapid drawdown and overtopping were compared and analyzed. Also, seepage analysis and slope stability analysis were performed for steady state and transient conditions. The pore water pressure and earth pressure for inclined core type showed high value at the base of the core, but they showed no infiltration by leakage. The pore water pressure and earth pressure by overtopping increased at the upstream slope and core, it is considered a useful data that can accurately estimate the possibility of failure of the reservoir. The behavior of failure due to overtopping was gradually enlarged towards the downstream slope from reservoir crest, and the inclined core after the raising embankment was influenced significantly to prevent the reservoir failure. The pore water pressure distribution for steady state and transient condition showed positive (+) pore water pressure on the upstream slope, it was gradually changed negative (-) pore water pressure on the downstream slope. The pore water pressure by overtopping showed a larger than the high water level at the downstream slope, it was likely to be the piping phenomenon because the hydraulic gradients showed largely at the inclined core and reservoir crest. The safety factor showed high at the steady state, and transient conditions did not show differences depending on the rapid drawdown.

• Geomechanics and Engineering
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• 제12권4호
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• pp.707-721
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• 2017

The objective of this paper is to experimentally study the consolidation of saturated silty clay subjected to repeated heating-cooling cycles using a modified temperature-controlled triaxial apparatus. Focus is placed on the influence of the water content, confining pressure, and magnitudes and number of thermal loading cycles. The experimental results show that the thermally induced pore pressure increases with increasing water content and magnitude of thermal loading in undrained conditions. After isothermal consolidation at an elevated temperature, the pore pressure continues to decrease and gradually falls below zero during undrained cooling, and the maximum negative pore pressure increases as the water content decreases or the magnitude of thermal loading increases. During isothermal consolidation at ambient temperature after one heating-cooling cycle, the pore pressure begins to rise due to water absorption and finally stabilizes at approximately zero. As the number of thermal loading cycles increases, the thermally induced pore pressure shows a degrading trend, which seems to be more apparent under a higher confining pressure. Overall, the specimens tested show an obvious volume reduction at the completion of a series of heating-cooling cycles, indicating a notable irreversible thermal consolidation deformation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 봄 학술발표회 논문집
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• pp.520-527
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• 2000

In the present study, the analytical approaches of vacuum consolidation with horizontal drains were proposed, For dissipating rapidly pore-water in hydraulic fills, vacuum consolidation method applied vacuum pressure in horizontal drains is developed. In the analytical approaches, the governing equation is based on two-dimensional finite strain consolidation theory and the boundary conditions of horizontal drains are considered in applying negative pore-water pressure occurred by vacuum pressure, Also, parametric studies to vacuum pressure and installation pattern of horizontal drains are carried out.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.743-750
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• 2002

Unsaturated soil has a possibility to induce a negative pore water pressure. Until now, saturated soil is mainly focused on the research of soil mechanics. Recently, soil mechanics is researched on two major parts such as saturated and unsaturated soil mechanics. Negative pore water pressure has a non-linear relationship with the water content changes. Soil-water characteristic curves of soil in Korea are not determined. There is no proper characteristic value such as air-entry value and residual water content. In this study, the characteristic curves of reclaimed soil, sand, and weathered granite soil were determined by laboratory tests. Air-entry value and residual water content were determined by fitting methods. Soil-water characteristic curves were estimated based on the particle-size distribution and compared with the laboratory test results. The results of soil-water characteristic curves estimation indicated that Fredlund and Wilson's model is excellent for sand and weathered granite soil. Arya and Paris's model is excellent for reclaimed soil.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.509-516
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• 2002

Rainfall-induced landslides in a weathered granite soil slope have mostly relative shallow slip surfaces above the groundwater table The pore-water pressure of soil above the groundwater table is usually negative. This negative pore-water pressure(or matric suction) has been found to make a large contribution to the slope stability. Therefore, the variation of in-situ matric suction profiles with time in a soil slope should be understood. In this study, a field measurement program was carried out from June to August, 2001 to monitor in-situ matric suctions and volumetric water contents in a weathered granite soil slope. The influence of climatic conditions on the variation of in-situ matric suctions could be found to decrease rapidly with depth. It could be found that decrement of matric suction induced by precipitation is affected not only by the amount and duration of rainfalls but also by the initial matric suction just prior to rainstorms. The soil-water characteristic from the field monitoring tends toward the wetting path of SWCC obtained from the laboratory test.

• 한국농공학회지
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• 제36권3호
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• pp.90-99
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• 1994

To investigate the undrained shear strength characteristics of marine soils with high water content, high compressibility and weak bearing capacity, a series of undrained triaxial tests with pore pressure measurements on undisturbed and disturbed Banwol marine clay in normally consolidated and overconsolidated states is carried out. The results and main conclusions of this study are summarized as follows : 1 . When the consolidation pressure is increased, the maximum deviator stress of disturbed and undistubed clay in normally consolidated state is increased. Pore pressure parameters and internal friction angle of undisturbed clay are greater than those of disturbed clay. 2. The relationship between pore pressure and axial strain of undisturbed clay in normally consolidated state can be expressed as a hyperbolic function like stress-strain relation proposed by Kondner. 3. In the pore pressure-axial strain relation of disturbed clay in normally consolidated state, failure ratio R'f is greatly deviated in the range of 0.7~0.9 proposed by Christian and Desai. 4. For overconsolided clay, when overconsolidation ratio (OCR) is increased, normalized maximum deviator stress is increased and maximum pore pressure is decreased gradually. 5. Cohesion of overconsolidated clay is greater than that of nomally consolidated clay and internal friction angle slightly is decreased. 6. Pore pressure parameter at failure (Af) of overconsolidated clay is varied with OCR, Af becomes negative values with increment in OCR

• 한국지반공학회논문집
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• 제31권8호
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• pp.5-15
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• 2015

불포화 지반에서 선행강우에 의한 강우침투특성을 분석하기 위하여 국내 편마암 풍화토에 대한 일차원 실내강우 침투실험을 수행하였다. 춘천 및 충주지역 시료에 대한 실내모형실험에서 불포화토의 음의 간극수압은 강우 재하시 급격히 감소하고, 강우 종료후 점차 회복되었다. 강우강도가 증가함에 따라 침투속도가 증가하였으며, 선행강우시보다 본강우에서 침투속도가 빠른 것으로 나타났다. 이는 선행강우에 의하여 증가된 지반의 높은 포화도가 본강우시 강우침투속도를 증가시킨 것으로 사료된다. 특히 점토함유량이 많은 충주시료에서 음의 간극수압의 회복 속도와 침투속도가 느리게 나타났다. 유한요소 사면안정에 대한 수치해석 결과는 강우 침투에 의한 음의 간극수압의 감소에 따른 사면 안전율을 감소와 강우 종료후 간극수압의 확산에 의한 추가적인 사면 안정성 저감을 보여주고 있다. 사면의 안전율은 선행강우시 보다 본강우에서 더욱 감소하였다. 선행강우는 불포화지반의 초기 간극수압의 크기와 깊이별 패턴에 지대한 영향을 미치며, 이는 강우 사면의 안정성 해석에 고려해야 할 중요한 요소이다.