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  137.Evaluating Stability and Functionality of Hybrid Erosion Control Dam for Reducing Debris Flow Damage in Forested Catchment Nea
Kidae Kim, Dongyeob Kim , Junpyo Seo, Changwoo Lee, Choongshik Woo,
Minjeng Kang, Sangseom Jeong, Dongkyun Lee


Abstract:The objective of this study was to develop erosion control dam for preventing disaster in consideration
of characteristics of forested catchment near urban area, and to assess its stability and functionality to see its
practicability in the field. Two types of hybrid erosion control dams were developed including debris flow prevention
dam by using pillar and float board screen type and debris flow control dam by using groyne. Also, review about
their static (sliding, overturning, bearing capacity) and dynamic (member force) stability was carried out. According
to the result, most of the assessed items met standard safety level although there were some cases where assessed
items were short of stability criteria against impact. Also, after miniature flume experiments based on the developed
erosion control dam to prove structure function (material catch, deposit), it turned out the dam decreased flow
sediment amount and velocity while increasing sediment-capturing capacity by 3.5 times on average compared to the
one controlled without erosion control dam. When function of erosion control dam for forested catchment near urban
area is quantified based on future flume experiments in a variety of conditions, the dams can be practically used in
the urban area, contribution to effectively reducing debris flow damage.

Keywords: debris barrier dam, soil erosion control dam, urban area, stability analysis, flume experiment

  136. Evaluation of Dynamic p-y Curve Based on the Numerical Analysis
Jeong-Sik Park, Sang-Seom Jeong

Journal of the Korean Geotechnical Society Vol. 33,(12),2017,pages 59~73

Abstract: Numerical analysis using 3D finite element program (PLAXIS 3D) evaluated the interaction of soil - pile structure under dynamic surface loading. The dynamic p-y curve of the 1-g shaking table experiment by numerical analysis was calculated, and the parametric studies were presented by considering the pile-soil condition, the pile tip condition, and
the loading condition. The frequency of 1.4 Hz is almost equal to the natural frequency of the pile - soil system. The p and y values of resonance phenomenon are significantly different from the results of other frequencies. The results can be summarized by a third order polynomial function representing the trend line in the p-y curve. In the case of a single pile, the shape of the dominant curve was found to be an ellipse by mathematical proof. The elliptic equation can be used for the dynamic design or analysis of soil-pile system.

Keywords: Numerical analysis, Dynamic p-y curve, Resonance phenomenon, 1-g shaking table model test

  135. Analysis of Plugging Effect for Large Diameter Steel Pipe Piles considering Driveability (CEL Method)
Sang-Seom Jeong, Jun-Young Ko, Su-Min Song

Journal of the Korean Geotechnical Society
Vol. 33,(12),2017,pages 21~33

Abstract: This paper presents the analysis for a plugging effect especially when the large diameter steel pipe pile was installed by considering driveability (BPM, blow per meter). The Coupled Eulerian-Lagrangian (CEL) technique was used to simulate the driving of open-ended piles into the soil. To consider the driveability, the applied driving energy for each pile was obtained from the analysis results using the wave equation. The parametric studies were performed for different pile diameters, penetration depths of the pile, soil elastic modulus, and BPM. It was found that the SPI is almost constant with increasing both the pile diameter and the required driving energy. It is also found that the plugging effect is increased with increasing the pile length, resulting in the increase of lateral earth pressure. Based on this study the apparent magnitude and distribution of the lateral earth pressure are proposed for inside portion mobilizing soil plug.

Keywords: Large diameter steel pipe pile, Large deformation FE analysis, Coupled Eulerian-Lagrangian technique, Driveability, Plugging effect, Soil Plugging Index(SPI), Lateral earth pressure coefficient

  134. Analysis of Load Sharing Ratio of Piled Raft Foundation by Field Measurement
Sang-Seom Jeong, Jun-Hwan Lee, Jong-Jeon Park, Yang-Hoon Roh, Moon-Hyun Hong

Journal of the Korean Geotechnical Society
Vol. 33,(8), 2017, pages 41~52

Abstract: In this study, field measurements were investigated to analyze the load sharing ratio and behavior of piled raft foundation. The field measurements were performed for about 300 days from the start of construction. The geometry of the raft is 3.1 m × 3.1 m, and the pre-cast and pre-bored pile is 23 m in length and 0.508 m in diameter. Based on the field measurements, the load-settlement relationship of the piled raft foundation was obtained, and the load sharing ratio of the pile was converged to 70% at ultimate loading condition. The load sharing ratio of the pile increased as the settlement increased, and this is because the surface friction of the weathered soil, which is at the lower ground, was significantly increased. Based on the results of the field measurements, load transfer curves were obtained and applied to a numerical analysis by using load transfer method.

Keywords: Piled raft foundations, Load sharing, Field measurement, Load-transfer curve, Load-settlement

  133. Analysis of Dynamic Behavior of a Single Pile in Dry Sand by 1g Shaking Table Tests
Hyun-sung Lim, Sang-Seom Jeong

Journal of the Korean Geotechnical Society Vol. 33,(7) ,2017,pages 17~28

Abstract: This paper presents the investigation of dynamic behavior of a single pile in dry sand based on 1g shaking table tests. The natural frequency of soil-pile system was measured, and then a range of loading frequency was determined based on the natural frequency. Additionally, the studies were performed by controlling loading accelerations, pile head mass and connectivity conditions between pile and cap. Based on the results obtained, relatively larger pile head displacement and bending moment occur when the loading frequency is larger than the natural frequency of soil-pile system. However, the slope of the p-y curve is smaller in the similar loading frequency. Also, it was found that inertia force like input acceleration and pile head mass, and relation of the natural frequency of soil-pile system and input frequency have a great influence on the slope of dynamic p-y curve, while pile head conditions don’t.

Keywords: 1 g shaking table test, Natural frequency, Dynamic p-y curve, Dry sand, Single pile

  132. Analysis of Skin Friction Behavior in Prebored and Precast Piles Based on Field Loading Test
Gyung-Ja Jung, Do-Hyun Kim, Chul-Ju Lee, Sang-Seom Jeong

Journal of the Korean Geotechnical Society Vol. 33, (1), 2017, pages 31 - 38

Abstract: Skin friction of prebored and precast pile may be one of the most critical factors affecting the bearing capacity and settlement. Special attention was given to the interface behavior of pile-cement milk-surrounding soil when the load is acting on the prebored and precast pile. The cases of single pile were analyzed through a three-dimensional finite element approach and pile loading tests. A series of numerical analyses of the interface of pile-cement milk-soil was conducted with the proposed t-z curve and field measurements. It is shown that the use of cement milk around the pile increases the skin friction and reduces the pile settlement. It is also known that the suggested t-z curve between the cement milk and the soil, enhances the accuracy of the numerical analysis results.

Keywords: Prebored and precast pile, Finite element method, Interface modeling, Load-settlement curve, t-z curve

  131. The Analysis of Skin Friction on Small-scale Prebored and Precast Piles Considering Cement Milk Influence
Jong-Jeon Park, Gyung-Ja Jung, Sang-Seom Jeong

Journal of the Korean Geotechnical Society Vol. 33, (1), 2017, pages 5 - 15

Abstract: Skin friction may be one of the most critical factors in designing the prebored and precast pile. Special attention was given to the interface behavior of cement milk-surrounding soil during the installation of prebored and precast pile.
Small-scale field model pile test was conducted for the case of single pile. The size and geometry of the small-scale field model piles were designed with pile length 1.3m, boring diameter 0.067 m. Quick maintain-load test was conducted for the cases of boring diameter 150, 125, 90, 86, 74 mm and water-cement ratio 90, 70, 60%. It was shown that the bearing capacity of the pile increased as the cement-water ratio and cement milk thickness increased. Considering the scale effect between the small-scale model test and the actual construction site, it was found that cement milk thickness of 0.1∼0.4D (50∼200 mm) was reasonable for the stability of the structure. Also, the proper cement paste water / cement ratio was about 70% when considering the results of this study and quality control.

Keywords: Small-scale field model pile test, Prebored and precast pile, Load-settlement, Water/Cement ratio,
Boring diameter

  130. A Study on the Excavation Damage Zone (EDZ) under TBM Advancement Based on Large Deformation Technique (CEL)
Seoung-Yeon Lee, Do-Hyun Kim, Sang-Seom Jeong

Journal of the Korean Geotechnical Society Vol. 32, (12), 2016, pages 5 - 13

  129. A Proposed Analytical Model for the Debris Flow with Erosion and Entrainment of Soil Layer
Kwangwoo Lee, Hyundo Park, Sangseom Jeong

Journal of the Korean Geotechnical Society Vol. 32, (10), 2016, pages 17 - 29

  128. Influence Factors on the Degree of Soil Plugging for Open-Ended Piles
Sangseom Jeong, Junyoung Ko

Journal of the Korean Geotechnical Society Vol. 32, (5), 2016, pages 27 - 36

  127. A Study on the Rational Application of 3D Numerical Analysis for Anchored Earth Retaining Wall
Sangseom Jeong, Jaeuk Sim, Sungjune Lee

Journal of the Korean Geotechnical Society Vol. 32, (4), 2016, pages 29 - 39

  126. Rainfall Threshold (ID curve) for Landslide Initiation and Prediction Considering Antecedent Rainfall
Moonhyun Hong, Junghwan Kim, Gyungja Jung, Sangseom Jeong

Journal of the Korean Geotechnical Society Vol. 32, (4), 2016, pages 15 - 27

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