• Journal of the Korean Geotechnical Society
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• v.31 no.5
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• pp.35-46
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• 2015

In this study, the behavior of self-supported earth retaining wall with stabilizing piles was investigated by using a numerical study and field tests in urban excavations. This earth retaining wall can provide stable support against lateral earth pressures through its use of stabilizing piles that provide passive resistance to lateral earth pressures arising due to ground excavations. Field tests at two sites were performed to verify the performance of instrumented retaining wall with stabilizing piles. Furthermore, detailed 3D numerical analyses were conducted to provide insight into the in situ wall behavior. The 3D numerical methodology in the present study represents the behavior of the self-supported earth retaining wall with stabilizing piles. A number of 3D numerical analyses were carried out on the self-supported earth retaining wall with stabilizing piles to assess the results stemming from wide variations of influencing parameters such as the soil condition, the pile spacing, the distance between the front pile and the rear pile, and the pile embedded depth. Based on the results of the parametric study, the maximum horizontal displacement and the maximum bending moment significantly decreased when the retaining wall with stabilizing piles is used. Moreover, the horizontal displacement reduction effect of influencing parameters such as the pile spacing and the distance between the front pile and the rear pile is more sensitive in sandy soil, with a higher friction angle compared to clayey soil. In engineering practice, reducing the pile spacing and increasing the distance between the front pile and the rear pile can effectively improve the stability of the self-supported earth retaining wall with stabilizing piles.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.3
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• pp.125-131
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• 1989

Since the paved road suffers from various types of repeated loads for the duration of it's life, it is likely to cause permanent deformation and fatigue finaly destroying the pavement performance. Accordingly, if we are to keep the pavement performance in good condition, it is required to take staps to prevent such troubles from happening in each stage of pavement, and thus to improve the stability of pavement. We find it is quite important to settle the problems such as permanent deformation and fatigue rupture by repeated loads both on subbase course and on subgrade. In this regard, we examined the deformation characteristics of soil cements, on which repeated loads are applied. For the effective examination, we chose to use soil-cements made of cohesive soil and sandy soil respectively, which had $20kg/cm^2$ of unconfined compression strength, at the age of 7 days. The experimental results are: 1. The elastic modulus of soil cement from sandy soil is higher than that of soil cement from cohesive soil. 2. The elastic modulus thends to decrease as the repeated loads rund up to 1,000 times, while increasing between 1,000 times and $1{\times}10^5$ times. 3. Unconfined compression strength is seen to increase about 30%.

• Journal of the Korean Geotechnical Society
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• v.36 no.12
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• pp.57-68
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• 2020

In the case of two-dimensional analysis generally applied in the analysis of Earth Retaining Wall, mutual interference occurs due to earth pressure, when the excavation width is small, and in the section where the excavation width is small, and the resulting influence makes it difficult to secure reliability in the horizontal displacement of the retaining wall when performing 2-dimensional analysis in a section with a small excavation width. This study performed two-dimensional and three-dimensional finite element analyses on excavation depth (H) and excavation width (B) under various conditions for the H-pile earth wall, in the geological conditions of clayey soil, sandy soil, and weathered rock, and examined the relationship between excavation width and horizontal displacement according to each condition, to identify the boundary of the excavation width, which is the range of mutual interference caused by earth pressure. As a result, it was possible to clearly distinguish the analytical boundary according to the excavation width only in the clayey soils with relatively large horizontal displacement. It is concluded that it is reasonable to perform a 3D finite element analysis, which is similar to the actual behavior, if the excavation scale (B/H) is 2.0 or less, with the digging width less than 12 m at a digging depth of 10 m or less, and with the the one less than 24 m at a digging depth of 10 m or more, and that 2-dimensional finite element analysis may be used in cases where the excavation width is greater than 12 m when the excavation scale (B/H) is 2.0 or more and the excavation depth is 10 m or less, and the excavation width is greater than 24 m at an excavation depth of 10 m or more.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.131-136
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• 2006

일면전단시험은 전단면의 응력을 직접 측정하므로 평면변형시 강도를 파악할 수 있는 등의 많은 장점을 가지고 있으며, 시험조작이 간편하기 때문에 실용적으로도 우수한 것으로 판단된다. 그러나 사질토의 경우에 의한, Dilatancy에 의한 체적변화과정에서 공시체와 전단상자의 주면마찰력이 전단면의 수직 응력을 증감시키기 때문에 구해지는 강도가 과대 또는 과소하게 나타나는 것으로 알려져 있다. 그러나 반력판측에 장착한 하중계를 통해 전단면의 수직응력을 직접 측정 제어하는 형식으로 개선되어 주면마찰력의 영향을 해소하였다. 따라서 본 연구는 반력판측에 하중계를 장착한 개량형 다단식 단순전단시험기를 개발하여 사질토의 정압(CD)조건 전단시험을 수행하여 강도특성과 전단강도에 미치는 영향을 개량형 일면전단시험의 결과와 비교하였다. 그 결과 정압조건의 일면전단시험과 단순전단시험에 의한 강도정수는 조밀한 모래의 경우는 거의 비슷하게 나타나며, 느슨한 모래의 경우는 일면전단이 다소 크게 나타났다. 그리고 단순전단과 일면전단시험에서의 Dilatancy거동에는 큰 차이가 나타나지 않았다.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.99-107
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• 2004

Anisotropic characteristics of deformation are important to understand the particular behavior in the pre-failure state of soils. Recent experiments show that cross-anisotropic moduli of granular soils can be expressed by functions of normal stresses in the corresponding directions, which is closely linked to micromechanical characteristics of particles. Granular soils are composed of a number of particles so that the force-displacement relationship at each contact point governs the macroscopic stress-strain relationship. Therefore, the micromechanical approach in which the deformation of granular soils is regarded as a mutual interaction between particle contacts is one of the best ways to investigate the anisotropic elastic deformation of soils. In this study, a numerical program based on the theory of micromechanics is developed. Generalized contact model for the irregular contact surface of soil particles is adopted to represent the force-displacement relationship in each contact point far the realistic prediction of anisotropic moduli. To evaluate the model parameters, a set of analytical solutions of anisotropic elastic moduli is derived in the isotropic stress condition. A detailed procedure to determine the model parameters is proposed with emphasis on the practical applicability of micromechanical program to analyze the elastic behavior of the granular soils.

• Journal of the Korean Geosynthetics Society
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• v.15 no.2
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• pp.25-33
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• 2016

This study was a basic research to obtain the knowledge of physical properties of the upper sedimented sandy soil in the Nakdong river delta area. The characteristics of shear strength and permeability with fine content and relative density were also investigated. The upper sedimented sandy soil near paddy and lower soft clay layers showed high percentage of fine content, and the rest parts had about 5% of fine content. The specific gravity regardless of depth and location was almost constant. The upper sedimented sandy soil mostly had particle size about 0.1 ~ 0.4mm regardless of sedimentation environment and has illite, a clay mineral, in the entire soil samples. The results of direct shear tests on remolded specimens of the upper sedimented sandy soil revealed that the friction angle and cohesion increased with relative density, but its effect was not significant. The fine content was significant, that as increasing it, the friction angle decreased and cohesion increased linearly. The permeability decreased with relative density and fine content, and the permeability of soil containing more than 15% of fine content was independent on the relative density.

• Journal of the Korean Geotechnical Society
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• v.31 no.6
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• pp.45-58
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• 2015

The aim of this study is to suggest a semi-empirical equation for estimating the hydraulic conductivity of sands using geoelectrical measurements technique. The suggested formula is based on the original Kozeny-Carman equation; therefore varying factors affecting the Kozeny-Carman equation were selected as the testing variables, and six different sands with varying particle sizes and particle shapes were used as the testing materials in this study. To measure both hydraulic and electrical conductivities, a series of constant head permeameter tests equipped with the four electrodes conductivity probe was conducted. Test results reveal that the effects of both pore water conductivity and flow rate in relation between hydraulic conductivity and formation factor (=pore water conductivity / measused conductivity of soil) of tested materials are negligible. However, because the variations of hydraulic conductivity of the tested sands according to particle sizes are significant, the estimated hydraulic conductivity using the formation factor varies with particle sizes. The overall comparison between the measured hydraulic conductivity and the estimated hydraulic conductivity using the suggested formula shows a good agreement, and the variation of hydraulic conductivity with varying Archie's m exponents is smaller compared with varying porosities.

• Journal of the Korean GEO-environmental Society
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• v.5 no.2
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• pp.51-62
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• 2004

Granular compaction piles have the load bearing capacity of the soft ground increase and have the settlement of foundation built on the reinforced soil reduce. The granular compaction group piles also have the consolidation of the soft ground accelerate and have the liquefaction caused by earthquake prevent using the granular materials such as sand, gravel, stone etc. However, this method is one of unuseful methods in Korea. The Granular compaction piles are constructed by grouping it with a raft system. The confining pressure at the center of bulging failure depth is a major variable in relation to estimate for the ultimate bearing capacity of the granular compaction piles. Therefore, a share of loading is determined considering the effect of load concentration ratio between the granular compaction piles and surrounding soils, and varies the magnitude of the confining pressure. In this study, method for the determination of the ultimate bearing capacity is proposed to apply a change of the horizontal pressure considering bulging failure depth, surcharge and loaded area. Also, the ultimate bearing capacity of the granular compaction piles is evaluated on the basis of previous study on the estimation of the ultimate bearing capacity and compared with the results obtained from laboratory scale model tests. And using the result from laboratory model tests, it is studied increase effect of the bearing capacity on the granular compaction piles and variance of coefficient of consolidation for the ground.

• Geophysics and Geophysical Exploration
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• v.13 no.1
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• pp.102-108
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• 2010

The internal structure of a river embankment must be delineated as part of investigations to evaluate its safety. Geophysical methods can be most effective means for that purpose, if they are used together with geotechnical methods such as the cone penetration test (CPT) and drilling. Since the dyke body and subsoil in general consist of material with a wide range of grain size, the properties and stratification of the soil must be accurately estimated to predict the mechanical stability and water infiltration in the river embankment. The strength and water content of the levee soil are also parameters required for such prediction. These parameters are usually estimated from CPT data, drilled core samples and laboratory tests. In this study we attempt to utilise geophysical data to estimate these parameters more effectively for very long river embankments. S-wave velocity and resistivity of the levee soils obtained with geophysical surveys are used to classify the soils. The classification is based on a physical soil model, called the unconsolidated sand model. Using this model, a soil profile along the river embankment is constructed from S-wave velocity and resistivity profiles. The soil profile thus obtained has been verified by geotechnical logs, which proves its usefulness for investigation of a river embankment.

• Journal of Bio-Environment Control
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• v.24 no.3
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• pp.187-195
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• 2015

In this study, a field test of uplift load was carried out using 15 greenhouse foundations fabricated in full scale on a sand soil to examine the uplift capacity of plastic film greenhouse and glasshouse foundations for disasterproof standard. As a result, the maximum uplift capacity of the target greenhouse foundations was shown to be in the range from 11.6kN to 82.4kN according to the differences between the forms and sizes of the foundation. As a result of the examination of the applicability using the field uplift load test result of the theoretical equation proposed for maximum uplift capacity calculation of greenhouse foundations, we found that in general, the conventional theoretical equation for the calculation provided numerical values close to the field test results. However, the soil considered in this study was a sand; thus, in the future, verifying the conventional theoretical equation for the uplift capacity calculation of a cohesive soil would be necessary.