모래와 세립토로 구성된 소수성 흙의 습윤성 분석

박정준,이기철,유승경,윤중만,홍기권 한국지반신소재학회 2023 한국지반신소재학회 논문집 Vol.22 No.4

본 연구에서는 흙 입자 표면이 소수성으로 구현된 사질토에 대하여 세립분 함유율이 사질토의 습윤성에 미치는 영향을 평가하기 위한 시험을 수행하였다. 습윤성은 주문진 표준사와 세립토가 함유된 사질토에 대하여 물방울 시험 결과로부터 얻은 접촉각으로 평가하였다. 시험 결과, 모래와 세립토로 구성된 사질토의 습윤성은 소수성 수준과 세립토 함유율 조건에 따라 변화하였다. 세립토 함유율이 사질토의 습윤성에 미치는 영향을 평가한 결과, 5% 세립토 함유율 조건에 있어서 소수성 수준이 1%와3%인 사질토의 접촉각은 표준사의 접촉각에 비하여 각각 94.4%, 32.4%가 감소하였다. 그리고, 소수성 수준이 5%인 경우, 5%와 10%의 세립토 함유율 조건에 대한 접촉각 감소율은 각각 24.4%와 37.3%였다. 즉, 세립토 함유율은 사질토 접촉각의크기 및 증감율에 큰 영향을 미치기 때문에, 오염물 거동 예측에 있어서 지반의 세립토 함유율에 따른 습윤성 평가가 수반되어야 한다. This study described the test results to evaluate the effect of fines content on the wettability of sandy soil composed of hydrophobic soil particles. Wettability was evaluated using the contact angle obtained from the water drop test results for Jumunjin standard sand and sandy soil containing fines content. The test results showed that the wettability of sandy soil composed of sand and fine-grained soil changed depending on the hydrophobic level and fines content. The influence of fines content on the wettability of sandy soil was analyzed. It was found that 1% and 3% hydrophobic sandy soil with 5% fines content decreased by 94.4% and 32.4%, respectively, compared to the contact angle of standard sand. In addition, the contact angle reduction ratio for sandy soil with a 5% hydrophobic level and a fines content of 5% and 10% were 24.4% and 37.3%, respectively. In other words, the wettability of the soils should be evaluated considering the fines content to predict the behavior of contaminants, because the fines content has a significant impact on the value and increase/decrease ratio of the contact angle of sandy soil

Fine Particles Migration in High-Clay Content Dredger Fill under Step Vacuum Preloading

( Xiaoqing Yuan ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Vacuum preloading is a soft ground improvement method that has been widely used in many reclamation projects. However, achieving the expected consolidation effect when dealing with high-clay content dredger fill is difficult. The reason is that the vacuum load is usually a one-off operation at 80 kPa in practical, in cases where fine particles of the dredger fill with insufficient structural strength will migrate to the prefabricated vertical drains (PVDs) due to a powerful vacuum suction effect, when a large number of fine particles accumulate at the PVDs and reach a certain thickness, the fine particles will plug the PVDs. Eventually, the PVDs are unable to provide a drainage channel for drainage consolidation, thereby reducing the consolidation efficiency of the dredger fill. The Step Vacuum Preloading method was proposed to reinforce the high clay dredger fill instead of the traditional vacuum preloading method, changing the one-off set to the means of three times step by step in order to make dredger fill to be consolidated fully and reduce the migration of fine particles. In this study, a step vacuum preloading indoor simulation test was conducted, the distribution data of particles in the process of step vacuum preloading monitoring was obtained and the law of fine particles migration is summarized. Furthermore, the mass ratio of silt and clay was primary defined as aggregate clay ratio to reflect the status of migration process. The “aggregate clay ratio” is considered as the indicator of fine particles migration.

Bottom Ash의 액상화 저항특성 연구

윤원섭,채영수 한국지반공학회 2011 한국지반공학회논문집 Vol.27 No.6

In this study relative density tests of bottom ash and standard sand were carried out. And cyclic triaxial tests for samples with the relative density of 40%, 55%, and 70% were carried out on the basis of the test results. Cyclic triaxial tests were also conducted for fines content with 55% relative density. Residual samples were divided into No.40, No.60, No.100, and No.200. In order to avoid crashing that can happen when compaction of the sample is initiated, bottom ash was crushed using the a compact mold. In consideration of the crushing characteristics of each residual samples, the fragmentation rate increased up to 30%, which led to the adjustment of fine-grained amount to 10%, 20%, and 30%. Through the repative triaxial test in accordance with the relative density, resistant characteristics of the liquefaction of bottom ash was analyzed. Test results show that, crushing strength of bottom ash was smaller than that of standard sand, resulting in different liquefaction behavior characteristics. And we could find fines content with maximum resistant characteristics of the liquefaction.

남극 장보고기지 현장시료의 액상화거동 특성 연구

박근보(Keunbo Park),김영석(YoungSeok Kim) 한국지반신소재학회 2014 한국지반신소재학회 논문집 Vol.13 No.2

본 연구에서는 남극 장보고기지 부근에서 채취한 시료를 활용하여 동하중에 대한 액상화 저항특성을 파악하기 위하여 반복삼축시험을 실시하였다. 또한 기존문헌과의 비교를 통하여 남극에서 퇴적된 지반의 동적거동을 규명하였다. 시험결과 동일한 압밀응력비에 대한 반복회수와 축변형률 5%를 발생시키는데 필요한 반복응력비와의 관계는 모든 시료에서 초기액상화를 발생시킬 수 있는 반복응력비가 증가할수록 반복회수가 감소하였다. 세립분 함유량이 10%로 증가할수록 액상화 저항강도가 감소하다가 다시 증가하는 경향을 나타내었다. 점착력과 액상화 저항강도와의 관계는 세립분 함유량과 액상화 저항강도와의 관계와 같이 점착력이 증가할수록 액상화 저항강도도 감소하지만 어느 시점 이후에는 반복응력비가 증가하는 경향을 보였다. 또한, 마찰각과 평균입경이 증가할수록 반복응력비가 증가하는 경향을 나타내었다. In this study, in order to take advantage of samples collected in the Jangbogo station, and to grasp the liquefaction resistance characteristics of the dynamic load was performed cyclic triaxial test. Also, through the comparison with the existing literature. The test results, for the relationship between number of cycles for the same cyclic shear stress ratio and the cyclic shear stress ratio to produce an axial strain of 5%, in all samples, the cyclic shear stress ratio to liquefaction for the specimen, which has been liquefied, was increased, whereas number of cycles were reduced. The cyclic shear stress ratio of samples first decrease up to the fine content of about 10%. After this strength level, there is a little increase in cyclic shear stress ratio with increasing fine content. In addition, the cyclic shear stress ratio between cohesive strength, mean particle size, and friction angle decrease but some time later, there was a tendency that cyclic shear stress ratio is a little increased.

Fines-PCC 복합충전제 제조 최적화 연구: 전단력의 영향

박재준,강현,조병욱 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

국내 제지산업은 국제 펄프 가격변동에 영향을 받지 않고 글로벌한 경쟁력을 가지기 위해 끊임없이 노력하고 있다. 상대적으로 고가인 펄프의 사용을 줄이고 저가인 충전제 함량을 증가시켜 생산 원가를 절감시키는 것이 대표적 경향이다. 충전제의 사용량을 증가시키면서, 동시에 저하되는 종이의 강도 저하를 완화시키기 위하여 본 연구팀은 미세분과 충전제를 선응집시켜 복합충전제(fines-PCC composite filler)를 제조하는 기술을 개발하였다. 복합충전제가 원가 절감 및 종이의 강도저하 문제점을 동시에 해결 할 수 있는 것으로 기대하고 있다. 종이의 회분율을 증가시키면서, 저하되는 종이의 감소율을 최소화하기 위하여, 복합충전제 제조 최적화에 대한 연구가 진행 중이다. 본 연구에서는 복합충전제 제조 시, 전단력에 따른 복합충전제의 평균 입도와 이것이 종이 물성에 미치는 영향을 토론할 것이다. 교반속도 조절을 통해 종이의 강도 및 종이의 구조 조절이 가능함을 확인하였다

모래의 입도분포와 세립분 함유량에 따른 액상화 저항특성 비교

서혁,김대현 조선대학교 공학기술연구원 2019 공학기술논문지 Vol.12 No.1

he liquefaction phenomenon occurs when the groundwater is pumped up through the top of sediments as the pore pressure increases due to the earthquake. There have been many studies on the loose sandy soils and various samples through repeated triaxial compression tests and shaking table tests, but there have been few studies on the effects of particle size distributions and the fine contents of sand on the liquefaction of sand. In this study, the undrained repeated triaxial compression tests were performed on sands with different particle size distributions, confining pressures, relative densities, and deviatoric stresses. The results of analysis showed that, with increasing relative density, SW(Well-graded sand) samples had higher liquefaction strength than SP(Poor-graded sand) samples. This is due to the lower void ratio of sand in SW samples than in SP samples. It was also found that the liquefaction strength decreased with a high fine content due to he rapid destruction of the filling of fine particles between the soil particles, leading to lower liquefaction strength.

Micro X-ray CT 촬영을 통한 동결 사질토 시료의 세립분 함유량에 따른 입자간 거리 분석

채덕호(Deokho Chae),이장근(Jangguen Lee),김광염(Kwang-Yeom Kim),조완제(Wanjei Cho) 한국지반환경공학회 2017 한국지반환경공학회논문집 Vol.18 No.1

Chae et al.(2015)에 따르면 동결 사질토의 역학적 거동은 동결온도와 세립분 함유량에 따라 크게 영향을 받는 것으로 나타났다. 이러한 원인으로 동결온도에 따른 부동수분의 차이일 것이라는 의견과 세립분 함유량 및 간극 내 얼음에 의해 사질토 입자들 이격거리 차이에 의한 것이라는 의견이 제시되었다. 제시된 두 가지 의견 중 사질토 입자들 이격거리의 확인을 위해 micro X-ray CT 촬영을 수행하였다. X-ray CT 촬영에 의한 비파괴 검사는 최근 지반공학 분야에서 진행되고 있는 다양한 융복합 연구 중 하나로 CT 촬영을 통하여 지반재료의 내부 구조를 마이크로미터 단위의 높은 해상도를 통해 평가할 수 있는 방법이다. 본 연구에서는 -5, -10, -15℃의 동결온도에서 성형된 5, 10, 15%의 세립분을 포함하고 있는 동결 사질토 공시체에 대하여 micro X-ray CT 촬영을 수행하고 기존의 개발된 이미지 해석 기법을 적용하여 동결 사질토 내의 조립질 입자들의 최단거리 및 평균거리를 통하여 세립분 함유량 및 동결온도가 조립질 입자간의 거리에 미치는 영향을 파악하고자 하였다. X-ray CT 촬영 결과, 동결온도 및 세립분 함유량은 동결 사질토 내 입자간 거리에는 큰 영향을 미치지 않는 것으로 나타났다. The mechanical characteristics of frozen sand greatly depend on the frozen temperature and the fine contents according to the previous study by Chae et al. (2015). There are two hypotheses to explain this experimental results; one is the unfrozen water contents greatly affected by the fine contents and frozen temperature and the other is the sand particle spacing greatly affected by the pore-ice. To evaluate the latter hypothesis, the micro X-ray CT scan was performed. The micro X-ray CT scanning, one of the actively performed interdisciplinary research area, has a high resolution with micrometer unit allows to investigate internal structure of soils. In this study, X-ray CT technique was applied to investigate the effect of the frozen temperature and fine contents on the sand particle minimum and average spacing with the developed image processing techniques. Based on the spacing analysis, the frozen temperature and fine contents have little influence on the sand particle spacing in the frozen sand specimens.

지하수위와 세립분 함유량에 따른 지반함몰 메커니즘

김진영,이성열,최창호,강재모,강권수,정효진,홍재철,이재수,백원진,Kim, JinYoung,Lee, SungYeol,Choi, ChangHo,Kang, JaeMo,Kang, KwonSoo,Jeong, HyoJin,Hong, JaeCheol,Lee, JaeSoo,Baek, WonJin 한국농공학회 2017 한국농공학회논문집 Vol.59 No.5

Recently, ground subsidence frequently occurs in downtown area. The major causes of the subsidence on the subsurface were the damages of the water supply and sewer pipelines and excavation works in adjacent areas, etc. Because of these various factors, it is not easy to analyze the tendency of occurrence of ground subsidence. The purpose of this study is to clarify the effect of ground subsidence by the change of the fine particle content and ground water level and to establish the ground subsidence mechanism. In this study, a model soil-box was manufactured to simulate the failure of the old sewer pipe which is one of the causes on ground subsidence. And a model test was conducted to investigate the effects of fine contents and ground water level on the cavity occurrence. From the test results, firstly the higher the ground water level, the faster the primary cavity is formed as the seepage stress increases. As a result, the secondary cavity and the ground subsidence rapidly progress due to the relaxation of the surrounding ground. The total amount of discharged soil was decreased as the fine content increased.

동결융해 반복에 따른 철도노반재료의 전단강도 변화

최찬용(Choi Chan yong),신은철(Shin Eun chul),강현회(Kang Hyoun Hoi) 한국지반환경공학회 2011 한국지반환경공학회논문집 Vol.12 No.7

동절기와 해빙기의 기온차가 큰 지역에서는 일정 깊이까지 동결, 융해 작용이 반복적으로 발생하여 흙의 역학적 특성이 변화를 보이게 된다. 특히 세립분이 많은 흙인 경우 팽창과 수축을 통한 입자의 재배열 등으로 인하여 노반의 연약화가 많이 발생된다. 이러한 노반의 연약화는 지지력이 낮은 지반에서 반복하중이 재하 되었을 때 급격하게 나타날 수 있다. 본 연구에서는 국내의 철도 노반재료로 사용되는 대표 토질 3가지를 대상으로 세립분의 함유량, 간극비의 영향 등을 고려하여 동결융해 반복횟수에 따른 직접전단 시험을 실시하여 그 감소량을 정량적으로 평가하였으며, 이를 통하여 세립분의 함유량과 함수비 조건, 동결융해 횟수 등을 고려할 수 있는 전단강도 저감 모델 식을 제안하였다. In seasonal frozen areas with climatic features, which have a temperature difference in the winter and thawing season, changes of mechanical properties of the soil in the zone could be seen between the freezing and thawing surface. In particular, in soil with many fine particles, a softening of the roadbed usually occurs from frost and thawing actions. The lower bearing capacity is a rapidly progressive the softening of roadbed, and occurred a mud-pumping by repeated loading. In this study, the three kind of sandy soil with contents of fine particles were conducted by directly shear box test with the number of cyclic in freeze-thawing and the water content of soil. Subsequently, the relationship between the shear strength and freeze-thaw cycling time was obtained. The shear strength was decreased with the increase of the freeze-thaw cycling time. A shear stress deterioration of the soil with power function modal is proposal.

Fractal equations to represent optimized grain size distributions used for concrete mix design

Soumia K. Sebsadji,Kaddour Chouicha 사단법인 한국계산역학회 2020 Computers and Concrete, An International Journal Vol.26 No.6

Grading of aggregate influences significantly almost all of the concrete performances. The purpose of this paper is to propose practicable equations that express the optimized total aggregate gradation, by weight or by number of particles in a concrete mix. The principle is based on the fractal feature of the grading of combined aggregate in a solid skeleton of concrete. Therefore, equations are derived based on the so-called fractal dimension of the grain size distribution of aggregates. Obtained model was then applied in such a way a correlation between some properties of the dry concrete mix and the fractal dimension of the aggregate gradation has been built. This demonstrates that the parameter fractal dimension is an efficacious tool to establish a unified model to study the solid phase of concrete in order to design aggregate gradation to meet certain requirements or even to predict some characteristics of the dry concrete mixture.