• 한국농공학회지
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• 제36권4호
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• pp.87-94
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• 1994

The aim of the work descrihed in this paper is to study a characteristics of an unsaturated soil for the different matric suctions. To this end, a series of suction controlled isotropic and triaxial compression tests is conducted on silty sands. Matric suction is controlled by the axis translation technique using high air entry ceramic disk. Total volume change, air and water volume changes are measured by the device made for the experiment. The specimens are compacted using a half of Proctor compaction energy and with the water contents of 5% drier than the optimum moisture contents. Isotropic compression and triaxial compression tests are conducted on the specimen at each equilibrium state of matric suction. From test results, volume changes and deviator stresses are analyzed at each state and their relationships are formulated.

• 한국지반공학회논문집
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• 제37권1호
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• pp.17-27
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• 2021

불포화토의 함수특성시험은 오랜 기간이 소요된다. 이를 줄이기 위하여 고압 공기합입치 디스크를 마이크로 멤브레인으로 대체하였다. 마이크로 멤브레인을 적용한 함수특성시험을 수행하여 그 결과를 세라믹 디스크를 이용한 시험결과와 비교하였다. 5개 지역에 대하여 많은 시료를 분석한 결과 마이크로 멤브레인을 적용한 함수특성곡선은 세라믹 디스크를 이용한 시험결과와 유사한 것으로 검증되었다. 이로 인하여 마이크로 멤브레인을 이용하여 신속한 절차기법을 개발하여 많은 양의 함수특성 성과를 획득할 수 있게 되었다. 그리고 마이크로 멤브레인을 이용한 시험을 포함하여 총 5개지역 29개 시료에 대한 함수특성곡선 데이터베이스를 구축하였다. 국내 풍화토에 대하여 불포화 수리특성은 세 그룹으로 분류할 수 있었다. 각 그룹은 van Genuchten 모델 물성치 n값에 따라서 분류되며 n값은 간극비의 함수로 상관관계를 찾을 수 있었다.

• 한국농공학회지
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• 제39권1호
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• pp.93-101
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• 1997

This paper presents yield surfaces and hardening laws for describing the state of an unsaturated soil under isotropic compression and suction changes. The yield surface is formulated within the framework of hardening plasticity using two independent sets of stress variables : the excess of total stress over air pressure and the suction. And the application of the yield surfaces and hardening laws are confirmed from the result of the experiment. To this end a series of suction-controlled isotropic tests are conducted on clayey soils. Matric suction is controlled by the axis translation technique using high air entry ceramic disk. The specimens are compacted using a half of Proctor compaction energy with 5 % lower of water content than the optimum moisture contents. From test results, existence of the yield surfaces and an application of hardening laws to samples are confirmed by comparison between test and predicted results. And it is confirmed that LC yield locus is extened with the total plastic deformations induced by suction or stress changes, however, SI yield locus is only extended with the plastic deformations by induced suction changes.

• 한국농공학회지
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• 제38권3호
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• pp.101-110
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• 1996

The aim of the work described in this paper is to develope a constitutive model for the prediction of an unsaturated clayey soil and to confirm the application of the model. To this end a series of suction controlled isotropic and triaxial compression tests are conducted on clayey soils. Matric suction is controlled by the axis translation technique using high air entry ceramic disk. Total volume change, air and water volume changes are measured by the device made for the experiment. The specimens are compacted by dynamic compaction using a half of Proctor compaction energy with the water contents of 5% drier than the optimum moisture contents. From test results, volume changes and deviator stresses are analyzed at each state and their relationships are formulated. And the application of the model to clayey soils is confirmed by the comparison between test and predicted results. During drying-wetting and loading-unloading processes for isotropic states, the agreement between predicted and test results are satisfactory. And predicted deviator stresses are well agreed with the test results in shearing process, but volumetric strain is not well agreed with the test results in high suctions.