• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.175-183
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• 1999

Recently, problems related to vibrations of decomposed granite soils have acquired increasing attention in Korea because those soils cover approximately one third of the country. Both resonant column and cyclic triaxial test were performed to investigate deformation characteristics of unsaturated and cement-mixed decomposed granite soils in Suwon region. The important soil parameters in this respect are the shear moduli, dynamic moduli of elasticity and damping ratios. The dynamic parameters are influenced by variables such as strain amplitude, ratio of loading cycles, and degree of saturations, etc. Test results and data have shown that the optimum degree of saturation to the maximum shear modulus due to a capillary menisci effect was about 17~18 % at low strain amplitude and 10~15 % at intermediate strain amplitude. This paper suggests the range of threshold strain and mean shear modulus of decomposed granite soils in Suwon region. It also proposed the empirical relationship between the dynamic parameters for cement-mixed and non-mixed decomposed granite soils.

• Journal of the Korean Geotechnical Society
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• v.18 no.6
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• pp.83-101
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• 2002

Elastic waves provide an important information about the soil mass in the near-surface. Soil properties in relation to elastic wave parameters are clarified to facilitate the application of geophysical technique to soil characterization. As an example, experiments are performed to gain further insight into the behavior of unsaturated particulate materials using bender elements. The small strain stiffness is continuously measured on specimens subjected to drying, and changes in stiffness are related to changes in interparticle forces such as capillarity, bonding due to ion sharing, buttress effect due to fine migration, and cementation due to salt precipitation. The rate of menisci regeneration is studied after a perturbation as well. Finally, several phenomena associated with the evolution of capillary forces during drying are identified.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6C
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• pp.303-311
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• 2009

In this study, weakly cemented sand was cured at air dry condition with different periods (3, 7, 14, 21, 28 days) and its unconfined compressive strength was evaluated. As a result, the strength of specimens with low cement ratios such as 4 and 8% increases until 7 days curing but, after 7 days, their strength continuously decreases. The strength of specimens with relatively high cement ratios such as 12 and 16% increases up to 7 days curing and then stays almost constant until 21 days. After 21 days curing, their strength suddenly dropped down, which is much lower than the strength of 3 days curing specimen. A cemented sand and gravel called CSG, which is highly permeable, could be exposed to repetitive drying and wetting conditions due to rainfall or groundwater table change during curing. In this study, the weakly cemented sand is exposed to repetitive drying and wetting and then its unconfined compressive strength was evaluated. As a result, the strength of a specimen with 27 days drying condition following 1 day wetting was at maximum 35% lower than the one cured under 28 days drying. The strength degradation due to wetting decreases as a cement ratio increases. However, the strength of a specimen with repetitive drying and wetting increases as the number of wetting increases until 3 cycles. After 3 cycles of drying and wetting, the rate of strength increase decreases due to an insufficient water for hydration or stays constant. If the sufficient water supply is provided to cemented sand during curing, the target or design strength increase can be achieved. Otherwise, the strength degradation due to wetting should be considered at the design stage.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.468-474
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• 2010

최근 국내에서 연약지반개량을 위하여 적극 도입되기 시작한 차세대 지반처리기술인 경량혼합토공법의 배합설계에 대한 고찰을 하였다. 경량혼합토는 건설잔토나 준설토 및 현장에서 발생하는 점토나 실트질 흙을 사토처리 하지 않고 현장에서 유용할 수 있는 매우 경제적이고 환경적인 공법으로서 일본에서는 지난 10여년에 연간 수백만톤의 경량혼합토를 생산하여 건설현장에 적용한 실적을 보유하고 있다. 특히 폐자원(폐타이어가루, 왕겨)을 경량혼합토에 첨가하여 건설재료 재활용을 위한 역학적 실험을 수행하였다. 본 연구에서는 경량혼합토를 제작하기 위해 필요한 배합설계변수인 원료토의 중량, 함수비 및 기포재와 첨가할 물의 양, 그리고 강도를 발현하기 위하여 필요한 고화재로서 시멘트첨가량에 대한 최적의 배합설계에 대한 분석을 하였다. 지금까지 제안된 시멘트함유량은 초기의 경량혼합토 목표강도가 주어지면 원료토의 조건에 따라 원하는 비중과 강도를 토대로 적절하게 현장에 적합하게 결정하는 단계에 있으나 일부 현장에서 지나친 목표강도 설정으로 과대한 시멘트를 사용하는 사례가 많아 국가적으로 막대한 손실을 초래하고 있다. 본 논문에서는 경량혼합토의 목표강도을 분석하고 그에 따른 최적의 시멘트함유량을 제시하고자 한다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.37-44
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• 2017

Red mud is an inorganic by-product produced from the mineral processing of alumina from Bauxite ores. The development of alkali-activated slag-red mud cement can be a representative study aimed at recycling the strong alkali of the red mud as a construction material. This study is to investigate the optimum water content, compressive strength, water absorption and efflorescence of alkali-activated slag-red mud soil pavement according to binder type. The results showed that the optimum water content, moisture absorption coefficient and efflorescence area of alkali-activated slag-red mud soil pavement increased but the compressive strength of that decreased as the redmud content increased.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.50-50
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• 2019

최근 국지성 호우 및 하천 제방의 노후화로 인한 제방 붕괴 피해가 빈번히 발생하면서 제방의 안정성 및 표면 보강을 위한 다양한 연구가 시도되고 있다. 본 연구에서는 제방 붕괴에 따른 피해 최소화 및 대책을 수립하기 위한 방법으로 시멘트와 같은 지구온난화를 야기시키는 물질이 아닌 친환경 신소재 바이오폴리머를 흙과 혼합한 재료를 활용하여 제방의 내구성을 강화하기 위한 연구가 수행되고 있다. 이에 안동하천실증연구센터에서는 현장토를 사용하여 높이 1 m, 폭 3 m, 사면경사 1 : 2, 총 길이 5 m 의 중규모 제방모형을 제작하였으며, 공동연구기관인 카이스트에서 개발된 바이오폴리머와 흙을 적정 비율로 혼합한 바이오-소일을 제방 전면에 일정 두께로 피복하여 월류 발생에 따른 제방 안정성 평가 실험을 수행하였다. 1차 실험은 흙 제방 조건이며, 2 3차 실험은 제방 표면에 5 cm 두께로 신소재가 피복된 조건으로 안정된 결과 도출을 위해 반복 실험을 수행하였다. 제방 천단면 및 사면에서의 유속분포를 측정하기 위해 드론 및 비디오카메라를 활용한 LSPIV 기법을 적용하여 실험조건에 따른 표면유속과 월류 흐름이 제방 붕괴에 미치는 영향에 대해 비교분석하였다. 또한 그래픽 소프트웨어를 이용한 픽셀기반 영상분석 기법을 적용하여 시간에 따른 제방사면의 붕괴면적을 산정하여 신소재 피복에 따른 붕괴 지연효과 분석을 통한 신소재 활용 제방의 현장 적용가능성 및 안정성을 평가하였다. 본 연구결과, 흙 제방의 경우 월류 흐름 발생 직후 침식현상이 전개되어 유속분포가 집중되고 있었으며, 이후 발생하는 강한 수직흐름으로 인해 입자추적을 통한 분석이 더 이상 불가능하였다. 신소재 제방의 경우 월류 흐름 발생 직후 침식은 발생하지 않았으며 일정시간동안 유속분포가 유지되었다. 지속적인 월류 흐름으로 인해 제방 끝단에서 침식이 발생하였으며 이때 최대 유속은 3.3 m/s 로 나타났다. 또한 픽셀기반 분석을 통해 30초 단위로 표면손실률을 산정한 결과, 신소재 활용 제방(2, 3차)의 경우 같은 실험조건에도 불구하고 최종 붕괴시간은 약 3배의 차이를 보였으며, 양생 과정에서의 크랙 발생을 최소화한다면 월류 발생 시 상당한 붕괴지연효과가 있는 것으로 판단된다.

• Journal of the Speleological Society of Korea
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• v.30 no.31
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• pp.68-73
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• 1992

필자는 이번 중국 여행으로 중국속의 백두산에 올라가기는 하였으나 5m 밖이 보이지 않는 구름으로 천지는 물론 큰 바위도 볼 수가 없었다. 그러므로 필자가 본 백두산의 지질을 논할 수가 없다. 다만 정상에 오를 때에 보인 발 밑의 흙과 이에 섞인 흰색의 부석을 보았고 검은 돌조각을 보았을 뿐이다. 이도백하에서 버스로 백두산에 접근할 떼에 흔한 다공질 현무암을 볼 수 없었다. 정상 가까이에서 집차를 타고 포장된 길을 오를 떼에는 이미 구름속에 있었다. 또 도로 가는 시멘트로 완전히 포장되어 있었다. 그러므로 필자는 오로지 문헌에 의하여 백두산의 지질을 소개하고자 한다.(중략)

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.4
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• pp.87-96
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• 2004

As a special concrete, which is a mixture of soil, cement and water, has strength like regular concrete for pavement, soil cement has been used in various field such as pavement and soft soil improvement. The objective of this study was to investigate the characteristic of unconfined compressive strength and time dependent behavior of soil cement that is made from decomposed granite soil or coluvial and inorganic solidification liquid. The results showed that the unconfined compressive strength appears to increase as the amount of cement and curing time increase In addition, the strength seems to decrease with increase of the potion of fine particles(No 200 sieve). The result of XRD indicated that there is Vermiculite, the product of reaction, in the soil cement. The dynamic properties of material, such as shear complex compliance, shear complex modulus, and phase angle could be calculated from the hysteresis loop obtained from the Haversine Creep Tests. Finally, creep behavior was able to be predicted from these dynamic properties.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.2
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• pp.88-94
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• 2010

A reliability analysis method is proposed in this paper to quantitatively evaluate the risk for internal stability of a quay wall constructed on the deep cement mixed ground, differentiating from the companion paper that mainly describes the external stability. Failure modes for toe pressure, shear strength of improved ground and extrusion of unimproved soft soil are investigated and compared in the risk estimation of internal stability using MVFOSM, FORM, and MCS. From the reliability analysis results for internal stability of a quay wall, the variance and distribution type of the compressive strength of Deep Mixed Soil-Cement appear to be very affective to the failure probability. On the other hand, other random variables seem to be relatively very insensitive to the probability of failure. It is therefore very important to rationally and accurately determine the probabilistic properties of the in-site compressive strength of Deep Mixed Soil-Cement.

• Journal of the Korean Geotechnical Society
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• v.34 no.10
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• pp.5-16
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• 2018

The ever-increasing amount of waste vinyl is causing big environmental problems. In particular, those from farming industry are sometimes left on site or even illegally reclaimed due to the lack of environmental concerns and capacity for collection, which worsens the situation. It is, therefore, believed that the recycling of waste vinyl is the most ideal solution in the viewpoint of environmental preservation. In this context, the potential of vinyl strip as a ground reinforcing material is investigated to expand the application of waste vinyl recycling. In this study, a series of uniaxial compression tests and resonant column tests were performed for sand specimens reinforced with vinyl strips and cement to investigate their reinforcing effects on static and dynamic behaviors. The changes in the uniaxial compressive strength (UCS), the shear modulus and the damping ratio according to the mixing ratio of vinyl strips and cements were analysed for sand specimens, having 40% and 60% relative densities, under various mixing conditions. As a result, both the static and dynamic reinforcing effects of vinyl strip-cement mixture were confirmed and the optimum mixing ratio was proposed.