• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.11-20
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• 2018

Surplus soil is commonly used at construction sites, because suitable fill material is not always immediately available and leads to additional costs. However, most surplus soils do not meet the requirement of suitable fill material to achieve the stability and strength of embankments. In this study, Proctor compaction tests and field compaction tests were performed by installing geosynthetics to resolve the problems caused by compacting unsuitable soils. Compaction energy and the number of geosynthetics were changed under the type A- and D- and type A Proctor compaction tests (KS F 2312), respectively. The field compaction testing using geosynthetics was performed on surplus soils of high water content. Optimum water content and maximum dry density of compacted soil decreased and increased by reinforcing geosynthetics, respectively. Compaction curves behaved with geosynthetics as the compaction curves behaved with higher compaction energy. Efficient compaction was possible because the compaction energy increased to 2.10 and 2.71 times the compaction energy required to achieve the same maximum dry density with one and two geosynthetic layer(s), respectively. Furthermore, field compaction tests verified that efficient compaction was possible because the dry density of unsuitable surplus soils of high water content was increased by reinforcing geosynthetics.

• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.65-74
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• 2018

The degree of compaction of embankments is generally measured using the sand replacement method or a soil density gauge. However, these methods include coarse particles, which are relatively large. The degree of compaction is overestimated if the in-situ soil density is simply compared with the density obtained from a Proctor compaction test (KS F 2312, 2001), because the density of coarse particles is higher than that of soil. However, there is no recommended correction for the coarse particle ratio in Korea, thus intentionally increasing the degree of compaction for structures to which large loads are applied or for which compaction is critical. Here, a correction considering the Korean Proctor compaction test and the difference between the maximum allowable particle sizes was recommended after corrections for coarse particle ratios in other countries were collected and analyzed. The degree of compaction was re-estimated by applying the recommended correction to the results of both Proctor compaction and sand replacement tests. The degree of compaction without the correction of coarse particle ratio was overestimated, because the re-estimated degree of compaction decreased as the coarse particle ratio increased. The relatively accurate results obtained from the field application of the correction will offer long-term cost savings due to reduced maintenance fees during operation.

• The Journal of Engineering Geology
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• v.20 no.2
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• pp.191-202
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• 2010

In this study, the relationship between the settlements and the horizontal displacements according to embankment was analyzed at the marine sedimentary grounds for preparation of a site, and then the empirical equations of both the settlement and the horizontal displacement considering the embankment load and the thickness were proposed. To do this, the field and laboratory tests were performed at the improvement section where the pre-loading method was applied, and the field monitoring was performed using various sensors. Based on the results of the tests and monitoring, the ground deposits, soil characteristics and engineering properties were analyzed and the settlements and lateral movements were estimated by the Regression analysis. The ground deposits from the ground surface were composed of reclaimed soils, sedimentary soils and based rocks. The thickness of clay in the sedimentary soils layer was ranged from 3.9 m to 44.5 m. The embankment heights to improve the ground during pre-loading were constructed from 4.7 m to 7.8 m in each section. The settlements during embankment were ranged from 0.959 m to 2.217 m and the lateral movements were ranged from 0.048 m to 0.313 m. As the result of regression analysis, the equations of settlements and horizontal displacements according to embankments may be proposed as $s=0.02h^2+0.11h$ and ${\delta}=0.01e^{0.37h}$, respectively. The proposed empirical equations of the settlements and the horizontal displacements according to embankment on the marine sedimentary ground may be applied to the site where has a similar condition of study area.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1373-1380
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• 2010

The plate loading test(PLT) and the field density test are mainly used on the construction of embankments to control the compaction of a limited layer thickness. These two test methods are very time consuming and inefficient, but they are still commonly used as the methods of quality control for soil compaction. In the last 3 decades, many devices such as geogauge, light falling weight deflectometer(LFWD) and dynamic cone penetrometer(DCP) etc., have been introduced into the engineering market with the objective of acquiring in situ stiffness properties of the compacted soil layers. Recently, a new type of sensor, called compactometer, which in mounted on the drum of a roller and measures impact forces continuously with GPS, called as Continuous Compaction Control(CCC), has come into use in many countries such as America, Germany, Japan and so on. The main objective of this paper is to assess the potential use of these new devices as quality control and assurance devices for compacted soil layers. Based on this study, compactometer and the LFWD results werestrongly correlated with the result obtained from the PLT and the field density test.

• Journal of the Korean Society for Railway
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• v.16 no.1
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• pp.40-46
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• 2013

Based on Korean railway design standards, the thicknesses of the reinforced roadbeds of conventional and high speed railways are different, and so too, for the size distribution of the ballast particles. Accordingly, considerable cost would be required to increase operating speeds of conventional lines, in particular related to changing from a ballasted track system to a ballastless one. In this study, applicability of a roadbed which supports conventional ballasted track, for use as a ballastless track for a high speed rail line was examined. A reinforced roadbed for a conventional railway is 20cm thick, and the type of material used for a conventional reinforced roadbed is M-40 (crushed gravel for road embankments). A dynamics test was conducted to evaluate the occurrence of the permanent settlement of the track substructure. These results suggest that, without changes to the track substructure, an operational speed of 400km/h is feasible with a ballastless track. This result; however, is from laboratory experiments. Further studies, such as numerical analyses or field validation, are required.

• Journal of the Korean Geotechnical Society
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• v.32 no.12
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• pp.79-91
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• 2016

Geosynthetic-reinforced and Pile-supported (GRPS) embankment method is widely used to construct structures on soft ground due to restraining residual settlement and their rapid construction. However, effect of cyclic loading has not been established although some countries suggest design methods through many studies. In this paper, cyclic loading tests were conducted to analyze dynamic load transfer characteristics of pile-supported embankment reinforced with geosynthetics. A series of 3 case full scale model tests which were non-reinforced, one-layer-reinforced, two-layer reinforced with geosynthetics were performed on piled embankments. In these series of tests, the height of embankment and pile spacing were selected according to EBGEO (2010) standard in Germany. As a result of the vertical load parts on the pile and on the geosynthetic reinforcement measured separately, cyclic loads transferred by only arching effect decreased with strength geosynthetic-reinforced case. However, final loads on the pile showed no differences among the cases. These results conflict with previous studies that reinforcement with geosynthetics increases transfer load concentrated on piles. In addition, it is observed that the load transferred to pile decreases at the beginning of cycle number due to reduction of arching effected by cyclic loading. Based on these results, transferred mechanism for cyclic load on GRPS system has been presented.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.5-19
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• 2003

A series of centrifuge model tests were conducted to investigate the behavior of piled bridge abutments subjected to lateral soil movements induced by approach embankments. The effect of clay layer depth and the rate of embankment construction on piled bridge abutments are the main focus of this study. Tests were performed for two loading types: (1) incremental loading applied in six lifts to the final embankment height; (2) instant loading corresponding to the final embankment height applied in one lift quickly. A variety of instrumentations such as LVDTs, strain gauges, earth pressure transducers, and pore pressure transducers are installed in designed positions in order to clarify the soil-pile interaction and the short- and long-term behavior for piled bridge abutments adjacent to surcharge loads. Based on the results of a series of centrifuge model tests, the distribution of lateral flow induced by staged embankment construction has trapezoidal distribution. The maximum lateral soil pressure is about 0.75$\gamma$H at surcharge loading stage, and about 0.35 $\gamma$H at over 80% consolidated stage.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.4
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• pp.39-47
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• 1982

Geotextile effects as reinforcement and vertical drain materials are studied through the laboratory model embankments on weak clays. The experiments are carried out in four stages; no woven fabrics between clay-crushed stone boundary, fabrics between boundary with no initial pretensioning of fabrics, and fabrics between boundary with two different initial pretensionings of fabrics. In all stages, vertical drains utilizing non-woven fabrics are installed in the clay layer in square pattern to accelarate the consolidation. The experimental model has plane dimensions of $32cm{\times}330cm$. The height for the clay container is 60 cm. The 47 cm height of crushed stone embankment is constructed over the 50 cm deep clay layer. The time dependent pore pressures are measured utilizing the 8 piezometers installed symmetrically on both sides of the wall at different heights. The time dependent deformations are measured utilizing the LED indicating lamp matrix inserted in the crushed stone embankment and the dialgauges put on top of the clay layer where the crushed stones are not laid. The measurements are carried out for 10 days which is equivalent to the time required for the primary consolidation. Through the experimental study, an analytical procedure is developed to predict the time dependent embankment settlement even if the top of the clay layer is reinforced with woven fabrics. This can be done through measuring the maximum pore pressures developed in the clay layer and comparing with the theoretical maximum pore pressures when no reinforcing fabrics are employed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1377-1387
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• 2013

Most embankment of the reservoirs (99.1 %) have been constructed in the earth filled type in Korea because the construction of this type is less expensive and simpler than others such as concrete one. However, it has to be reinforced the slope to prevent the breach due to overtopping or piping under unexpected flood conditions. This study has been analyzed the retardation effect using three types (L, T, $L^*$ shape) of stiffener in order to reinforce embankment when they are collapsed by overtopping flow. Experimental results showed that L-type stiffener is the most effective in delaying the breaching of embankment and reducing the soil erosion when compared with others. The reinforced embankment breaching showed that time delay was occurred about 1.73 to 2.29 times and the peak flowrate was reduced compared to non-stiffener embankments due to energy dissipation by collision and less soil erosion. The embankment breaching mostly leads to major damages because of the lack of repair time. Thus, since these stiffeners can resist the rapid breach, it would be possible to earn the time to emergency repair and lifesaving, as well as reduction of damages of embankment in downward region with decreasing peak flowrate. Results from this study would be used for the basis when establishing the emergency action plan for the reservoirs on the verge of hazard.

• Geophysics and Geophysical Exploration
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• v.21 no.1
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• pp.8-14
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• 2018

For the purpose of maintenance and prevention of earth fill dams against damage from natural hazards, automatic monitoring through various measuring instruments and resistivity survey has been carried out. Reservoirs and embankments have the structural vulnerability on the agricultural usages since most of them were built more than thirty years ago. The main aim to use monitoring method is to verify the safety and integrity of the dam. Resistivity survey can detect potential weaknesses, such as defective zones, anomalous seepages or internal erosion processes. Permanent resistivity monitoring systems were installed at a reservoir, which daily measurements have been taken every 6 hour. Using monitoring data for one year, anomalous seepage and structural defects were clarified for dam safety. Annual water level fluctuations are around 10 m. During their operation, reservoir dams are subject to a never-ending hydraulic load from the reservoir, which over the years may cause changes in the properties of the inner parts of the dam construction. Detailed analysis of the monitoring results was performed and showed that resistivities at most locations have been very stable over the full monitoring period excluding the effects of water fluctuation and seasons. To investigate the detectability of weak zone using the DC resistivity monitoring, numerical modeling with a simplified model for the drainage at a reservoir dam was also performed. The results showed that the seepage zone near drainage in a reservoir dam could be detected by resistivity response change.