• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.121-128
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• 2005

This paper introduces a method of predicting the behavior of compacted soil with an unsaturated soil mechanics by considering the effect of suction as an increasing consolidation yield stress. Two kinds of experiments were conducted. One is a series of static compaction tests to monitor the suction, and the other is a series of compression tests on compacted soil without soaking. The results of our tests indicate that it is possible to derive the distribution of suction on compaction curves and to hypothesize the changes in void ratio in the compression tests that depends on the suction. In addition, a new method is proposed to estimate the consolidation yield stress of compacted soil with a simple chart including compaction curves.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 1998년도 공동 심포지엄 및 추계학술발표회
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• pp.216-220
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• 1998

Experimental studies were carried out to investigate water diffusion in unsaturated compacted bentonite for a landfill of hazardous wastes. Water content distributions were measured and water diffusion coefficients were determined when the dry densities of compacted bentonite were in the range of 1.4 - 1.8 g/㎤. Resaturation times were also calculated to analyze the ability of the compacted bentonite to retard water movement. The results obtained were as follows: Diffusion model described properly the water migration in unsaturated compacted bentonite. Water diffusion coefficients ranged from 4.30$\times$10$^{-6}$ $\textrm{cm}^2$/sec to 1.93$\times$10$^{-6}$ $\textrm{cm}^2$/sec, and decreased with increasing the dry density. The dry density of compacted bentonite was found to be an important factor to control the resaturation time by water. This study suggests that the domestic compacted bentonite should be a good barrier material against water movement in a landfill of hazardous wastes.

• Geomechanics and Engineering
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• 제20권2호
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• pp.155-164
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• 2020

In recent years, the stability, safety and comfort of trains has received increased attention. The mechanical characteristics and differential settlement of the foundation are the main problems studied in high-speed railway research. The mechanical characteristics and differential settlement of the foundation are greatly affected by the ground treatment. Additionally, the effects of train load and earthquakes have a great impact. The dynamic action of the train will increase the vibration acceleration of the foundation and increase the cumulative deformation, and the earthquake action will affect the stability of the substructure. Earthquakes have an important practical significance for the dynamic analysis of the railway operation stage; therefore, considering the impact of earthquakes on the railway substructure stability has engineering significance. In this paper, finite element model of the CFG (Cement Fly-ash Gravel) pile + cement-soil compacted pile about composite foundation is established, and manual numerical incentive method is selected as the simulation principle. The mechanical characteristics and differential settlement of CFG pile + cement-soil compacted pile about composite foundation under train load are studied. The results show: under the train load, the neutral point of the side friction about CFG pile is located at nearly 7/8 of the pile length; the vertical dynamic stress-time history curves of the cement-soil compacted pile, CFG pile and soil between piles are all regular serrated shape, the vertical dynamic stress of CFG pile changes greatly, but the vertical dynamic stress of cement-soil compacted pile and soil between piles does not change much; the vertical displacement of CFG pile, cement-soil compacted pile and soil between piles change very little.

• 한국지반공학회논문집
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• 제21권5호
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• pp.143-151
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• 2005

본 연구는 불포화토의 역학적 특성, 특히 메트릭 흡인력(matric suction)을 이용하여 다짐토의 압밀 항복응력을 산정하는 방법에 대해 검토되었다. 이를 위해, 두 종류의 시험을 실시하였다. 하나는 흡인력을 측정하기 위하여 정적 다짐시험이 실시하였으며, 다른 하나는 수침시키지 않은 다짐토의 압밀시험을 실시하였다. 그 시험 결과, 다짐곡선 상에 흡인력의 분포를 나타낼 수 있었으며, 압밀시험에서 간극비의 변화는 흡인력에 의존하는 것을 알 수 있었다. 이상의 시험결과를 기초로 하여, 다짐 곡선을 포함하는 다짐토의 압밀 항복 응력을 산정하는 새로운 방법을 제안하였다.

• Geomechanics and Engineering
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• 제22권3호
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• pp.237-244
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• 2020

To achieve a wide suction range, the low suction was imposed on compacted silt specimens by the axis translation technique and the high suction was imposed by the vapor equilibrium technique with saturated salt solutions. Firstly, the results of soil water retention tests on compacted silt show that the soil water retention curves in terms of gravimetric water content versus suction relation are independent of the dry density or void ratio in a high suction range. Therefore, triaxial tests on compacted silt with constant water content at high suctions can be considered as that with constant suction. Secondly, the results of triaxial shear tests on unsaturated compacted silt with the initial void ratio of about 0.75 show a strain-hardening behavior with a slightly shear contraction and then strain-softening behavior with an obviously dilation. As the imposed suction increases, the shear strength increases up to a peak value and then decreases when the suction is beyond a special value corresponding to the peak shear strength. The residual strength increases to fair value and those at high suctions are almost independent of imposed suctions. In addition, the contribution of suction to the strength of compacted silt would not diminish even in a high suction range.

• Geomechanics and Engineering
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• 제28권1호
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• pp.35-48
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• 2022

The effect of discrete polypropylene fibre reinforcement on shear strength parameters, tensile properties and isotropic index of stabilized compacted residual subgrade was investigated. Composites of compacted subgrade were developed from polypropylene fibre dosage of 0%, 1%, 2.5% and 4% and 3% cement binder. Saturated compacted soil benefited from incremental fibre dosage, the mobilized friction coefficient increased to a maximum at 2.5% fibre dosage from 0.41 to 0.58 and the contribution due to further increase in fibre dosage was marginal. Binder stabilization increased the degree of isotropy for unreinforced soil at lower fibre dosage of 1% and then decreased with higher fibre dosage. Saturation of 3% binder stabilized soil decreased the soil friction angle and the degree of isotropy for both unstabilized and binder stabilized soil increased with fibre dosage. The maximum tensile stress of 3% binder stabilized fibre reinforced residual soil was 3-fold that of 3% binder stabilized unreinforced soil. The difference in computed and measured maximum tensile and tangential stress decreased with increase in fibre dosage and degree of stabilization and polypropylene fibre reinforced soil met local and international criteria for road construction subgrade.

• 한국지반공학회논문집
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• 제15권5호
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• pp.43-55
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• 1999

본 연구는 익산다짐풍화 화강토를 사용하여 여러가지 응력경로 시험을 실시하고 관측된 거동을 정확하게 예측할 수 있는 능력으로서 Yasufuku구성모델을 평가하였다. Yasufuku구성모델로 계산된 변형률은 측정치와 대부분 잘 일치하지만 약간의 차이를 나타내기도 하였다. 측정한 변형률과 계산한 변형률 사이에 가장 큰 차이를 보인곳은 증가하는 응력을 갖는 비례하중이 작용할 때 축변형률에 대하여 일어났다. Yasufuku 구성모델은 익산다짐풍화 화강토의 거동을 일정 구속압력하에서 축하중이 작용할 때와 p'-일정하중이 작용할 때 정확하게 추정할 수 있었다.

• 한국농공학회지
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• 제21권2호
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• pp.81-103
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• 1979

The weathered granite soil involves problems in its stability in soil structures depending upon the reduction of soil strength due to the water absorption, crushability, and content of colored mineral and feldspar. As an attemt to solve the problems associated with soil stability, the crushability of weathered granite soil was investigated by conducting tests such as compaction test, CBR test, unconfined compression test, direct shear test, triaxial compression test, and permeability test on the five soil samples different in weathering and mineral compositions. The experimental results are summarized as follows: The ratio of increasing dry density in the weathered granite soil was high as the compaction energy was low, while it was low as the compaction energy was increased. The unconfined compressive strength. and CBR value were highest in the dry side rather than in the soil with the optimum moisture content, when the soil was compacted by adjusting water content. However, the unconfined compressive strength of smples, which were compacted and oven dried, were highest in the wet side rather than in soil with the optimum moisture content. As the soil becomes coarse grain, the ratio of specific surface area increased due to increased crushability, and the increasing ratio of the specific surface area decreased as the compaction energy was increased. The highest ratio of grain crushability was attained in the wet side rather than in the soil with the optimum moisture content. Such tendency was transforming to the dry side as the compaction energy was increased. The effect of water on the grain crushability of soil was high in the coarse grained soil. The specific surface area of WK soil sample, when compacted under the condition of air dried and under the optimum moisture content, was constant regardless of the compaction energy. When the weathered granite soil and river sand with the same grain size were compacted with low compaction energy, the weathered granite soil with crushability had higher dry density than river sand. However, when the compaction energy reached to certain point over limitation, the river sand had higher dry density than the weathered granite soil. The coefficient of permeability was lowest in the wet side rather than in the optimum moisture content, when the soil was compacted by adjusting soil water content. The reduction of permeability of soil due to the compaction was more apparent in the weathered granite soil than in the river sand. The highly significant correlation coefficient was obtained between the amount of particle breakage and dry density of the compacted soil.

• 한국지반공학회논문집
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• 제20권5호
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• pp.5-16
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• 2004

본 연구에서는 토목섬유로 보강된 다짐토의 보강 메카니즘이 제시되며, 이러한 보강 메카니즘은 다짐토의 체적팽창(부의 다일러탄시)을 토목섬유에 의해 구속 억제하는 과정에서 생성되는 효과로 간주된다. 먼저, 실내실험을 위한 구체적인 방법으로서, 토목섬유의 보강효과를 정량적으로 파악하기 위하여 사질토를 다짐하여 공시체를 만들어 그 주위에 토목섬유를 설치한 후 전체적으로 압축전단시험을 실시하였다. 실험에서 초기 다짐도는 각각의 종류에 대하여 다일러탄시의 특성이 다르기 때문에 각각의 공시체에 대하여 변화시켰다. 여기서 전단시험 도중에 다짐토의 다일러탄시 변형을 방지하기 위한 토목섬유에 작용하는 축방향 힘들(axial forces)이 조사되었다. 또한 다짐토의 탄소성 모델과 이러한 모델에 필요한 초기 입력치 값의 결정 방법들이 제시된다. 마지막으로, 탄소성 구성 모델에서 항복 이전의 탄성 영역의 거동을 모사하기 위하여 Hashiguch(1989)가 제안한 subloading surface의 개념을 도입하여, 유한요소(FEM) 해석을 통해 얻어진 결과들을 실내시험의 결과와 비교 분석하였다.

• 한국토양비료학회지
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• 제48권6호
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• pp.628-633
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• 2015

It is necessary to assess soil physical properties and crop growth treated by compaction to establish the soil management standard. This study evaluated the bulk density, strength and crop growth after subsoil compaction for sandy loam and loam on the field in Suwon, Korea. The treatments were compaction and deep tillage. Sandy loam and loam were classified to coarse soil and fine soil, respectively, depending on clay contents. In coarse soil, bulk density of compacted plot was 8~17% greater than control and deep tilled plot. The root growth was worse in compacted plot compared with control. In fine soil, plow pan was not observed in deep tilled plot with 5~19% smaller bulk density than compacted plot and control. Deep tillage improved the crop growth. The soil physical properties by compaction were dependent on clay content and crop growth limit depended on the traffic driving.