• Journal of the Korean GEO-environmental Society
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• v.22 no.12
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• pp.65-70
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• 2021

River-side Embankment collapse involves various causes. The embankment collapse due to internal erosion around embedded structures reaches up to more than 10% in Korea. Many studies are being attempted to prevent from the collapse of the embankment rooted from overtopping and instability as well as internal erosion. One of them is the study on the application of biopolymers. The application of biopolymers to soils are divided into enhancing strength, vegetation and erosion resistance. This study investigated the effect of biopolymer treated soil on erosion resistance. The main goal of the study is to obtain basic data for real-scale experiments to verify the effectiveness of biopolymer treated soil embankment including a review of the collapse pattern in the model embankment with various test conditions. The optimized experimental conditions were selected by examining the erosion patterns according to each induction path with three compaction degree of the model embankment. As a result of the experiment, the internal erosion rate in the embankment to which the biopolymer treated soil was applied is greatly reduced, and it could be concluded that it might be applied to the actual embankment. However, in this study, the conclusion was drawn only within the scaled-down model embankment. In order to practically apply the biopolymer treated soil to the embankment, the study considering the scale effect would be needed.

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.1159-1168
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• 2020

The conduits of agricultural reservoirs undergo deterioration over a considerable period of time and this is highly likely to cause structural problems such as cracks. It is therefore important to consider the effects of structural defects on the body from the viewpoint of stability and maintenance of the embankment. In this study, basic data on the effects of the crack location on the stability of the embankment is obtained by identifying, comparing, and analyzing the erosion characteristics and pore water pressure behavior through a large-scale model experiment that involves classifying the location of the conduit cracks. From the results of the experiment, it was confirmed that when a crack occurred, the amount of leakage increased as the location of the crack portion was closer to the water level, and the internal erosion phenomenon accelerated, thereby increasing the possibility of piping. It was also found that an upstream conduit crack affects the erosion and water pressure change of the central and downstream conduit of the embankment, and the conduit crack has a very large effect on the pore water pressure despite the low upstream water level. Therefore, the seepage behavior of the embankment for each conduit crack identified in this study is considered to be useful basic data for preparing a repair and reinforcement plan according to the crack location in the future.

• Journal of Korean Society of societal Security
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• v.1 no.4
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• pp.65-71
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• 2008

This paper presents the characteristics of internal erosion of embankment slopes due to the localized heavy rain. In this study, the existing analysis methods of filter performance in embankment materials were reviewed. Based on the theoretical concept of filter conditions to prevent particles from being carried in from the adjacent embankment materials, new analysis method was suggested. According to the new analysis method for filter performance, experimental programs were carried out to investigate the filter performance for controlling and sealing any leak which develops through the embankment materials as a result of internal erosion. Three sets of small scale laboratory tests were carried out with changing the main influence factors such as rainfall intensity, gradient of slope, embankment material condition. It was found that the new analysis method for filter performance to prevent particles from being carried in from the adjacent embankment materials was more capable approach to design the filter materials in embankment slopes. The new criterion or method for satisfactory filter performance, therefore, was recommended.

• Journal of the Korean Geotechnical Society
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• v.26 no.4
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• pp.59-68
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• 2010

Piping, a common form of internal embankment erosion, is caused by progressive movement of soil particles through an embankment. The phenomenon commonly occurs with precursory signs of development of fractures in dam structures, but also occurs without any noticeable signs in dams that showed satisfactory dam performance for several years, due to dissolution of soluble material in an embankment. While piping accounts for nearly 50% of the causes for dam failure, few studies have been made for systematic evaluation of the phenomenon. In this study, we attempted to monitor the changes in electrical resistivities of fill-dam material while a saddle dam is dismantled for the construction of emergency spillways of Daechung dam. Two artificial subhorizontal boreholes were drilled into the embankment structure to simulate piping along the two artificial flow channels. Monitoring of changes in electrical resistivity showed an increase in resistivity values during piping. Thus, the investigation of resistivity over time could be an effective method for piping prediction.

• Journal of the Korean Geotechnical Society
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• v.29 no.5
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• pp.53-64
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• 2013

Resistivity monitoring is based on the fact that a change in the porosity leads to the changes in water content and fine particles, which alter the electrical resistivity. At every embankment dam, internal erosion always occurs as time passes. The internal erosion generally develops into piping over a long time by backward erosion and concentrated leak, and finally leads to dam failure. Resistivity is known to be very sensitive to the changes in porosity in embankment dams. Thus resistivity monitoring is a reasonable method to find out the leakage zone. However, resistivity is strongly influenced by seasonal variation of temperature, TDS of reservoir water and water level. In this paper. we first installed electrodes permanently at the center of the crest. The electrical resistivity monitoring data was acquired every 6 hours from Apr. 3, 2011 to July. 31, 2012. To analyze the characteristics of monitoring data, each resistivity data was calculated from up to 2,950 data sets. The result indicated a seasonal resistivity variation due to related temperature. Finally, a quantitative method to estimate porosities of the embankment dam from the resistivity monitoring data was analyzed. The applicability and reliability were verified and the importance of electrical resistivity monitoring for obtaining reliable result was emphasized.

• Journal of the Korean Geotechnical Society
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• v.35 no.4
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• pp.5-14
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• 2019

The typical four conditions related to internal erosion were set from the results of the regular dam safety inspection for 17,500 dams, and a questionnaire survey was conducted for dam safety experts to quantify these four typical current dam conditions with scores between 0 and 10, respectively. In addition, we proposed 'possible score range' for each condition to minimize the decision limits for dam managers to quantify dam conditions while helping to quantify various dam conditions except 4 representative conditions. A case study based on 'quantified score' and 'possible score range' for each condition showed that this method consistently reflects the dangerousness of the dam and provides a reasonable probability of failure. This helps to overcome limitations of dam rating determination by weighted average, and it will help to evaluate dangerous dams as dangerous dams.

• Geomechanics and Engineering
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• v.18 no.5
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• pp.493-502
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• 2019

Internal stability is an important safety issue for levees, embankments, and other earthen structures. Since a large part of the world's population lives near oceans, lakes and rivers, floods resulting from breaching of dams can lead to devastating disasters with tremendous loss of life and property, especially in densely populated areas. There are some main factors that affect the internal stability of dams, levees and other earthen structures, such as the erodibility of the soil, the water velocity inside the soil mass and the geometry of the earthen structure, etc. Thus, the mechanism of internal erosion and stability of soils is very complicated and it is vital to investigate the assessment methods of internal stability of soils in embankment dams and their foundations. This paper presents an improved support vector machine (SVM) model to predict the internal stability of soils. The grid search algorithm (GSA) is employed to find the optimal parameters of SVM firstly, and then the cross - validation (CV) method is employed to estimate the classification accuracy of the GSA-SVM model. Two examples of internal stability of soils are presented to validate the predictive capability of the proposed GSA-SVM model. In addition to verify the effectiveness of the proposed GSA-SVM model, the predictions from the proposed GSA-SVM model were compared with those from the traditional back propagation neural network (BPNN) model. The results showed that the proposed GSA-SVM model is a feasible and efficient tool for assessing the internal stability of soils with high accuracy.

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.1
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• pp.81-88
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• 2006

Numerical analyses were carried out for studying on seepage problems due to seawater intrusion through the embedded rock layers of the sea-dike. A seepage analysis model, SAMTLE was developed fur two-layer embankment system. The analyses by SAMTLE showed that the size of embedded rock layer had a significant effect on the seepage problems of sea-dike. If the embedded rock layer is longer and thicker, the seepage problems become more serious to water head, seepage rate and safety factor of piping in embankment. On the other hand, if the width of embedded rock layer is equivalent to the sea-dike's bottom width, the water head becomes lower and seepage rate and safety factor of piping are dramatically increasing. This makes another seepage problems such that the fresh water becomes saltier and higher seepage rates result in internal erosion of sea-dike.

• Geophysics and Geophysical Exploration
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• v.25 no.3
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• pp.120-128
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• 2022

There are 17,000 reservoir dams in Korea, of which more than 85% were built over 50 years ago. Old embankment dams are weakened by internal erosion and suffusion phenomena due to preferential leakage paths and this ongoing weakening can cause their failure. Therefore, early warning associated with leakage in an embankment dam is crucial to prevent its failure. An electrical resistivity survey is a non-destructive, real-time and in-situ technique for detecting the development of leakage zones and general conditions of embankment dams. Because of its advantages, the electrical resistivity survey is widely used for reservoir safety inspections. However, the electrical resistivity survey is still not officially included in the precise safety inspection of reservoir dams because it cannot present a quantitative index of dam safety. In this study, we propose a method for calculating the leak index according to the water content evaluated from the electrical resistivity survey and/or induced polarization survey. Particularly, by proposing a quantitative leak index calculation method from monitoring surveys and independent surveys, we provide a theoretical basis for including electrical resistivity and induced polarization surveys as components of the precise safety inspection of reservoirs dams.

• Journal of the Korean GEO-environmental Society
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• v.19 no.4
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• pp.33-38
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• 2018

The internal erosion due to poor compaction of the material was the main cause of collapse of the embankment in Korea. The assessment of the compaction state of the dam body was a very important check in the safety diagnosis of the embankment. In this study, the correlation between dynamic cone penetration test and plate loading test which is the most typical compaction evaluation technique was analyzed to verify the applicability of the dynamic cone penetration test in evaluating the compaction state of the dam body. The standard penetration tests were carried out six times to define soil properties and depth of the test site. The spatial distributions were obtained by the Kriging method after 15 times of plate loading tests and 47 times of dynamic cone penetration tests. The Pearson correlation coefficient between the spatial distribution of the plate loading test and the dynamic cone penetration test spatial distribution at the constant penetration depth was calculated. The load distribution in the plate loading test and the blow counts at penetration depths of 5 cm, 10 cm and 15 cm in the dynamic cone penetration test showed a weak positive correlation.