• Wind and Structures
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• v.35 no.6
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• pp.405-418
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• 2022

The aerodynamic behaviour of a CRH high-speed train under three infrastructure scenarios (flat ground, embankment, and viaduct) in the presence of a crosswind was simulated using a 1/8th scaled train model with three cars and the IDDES framework. The time-averaged and instantaneous flow field around the model were examined. The employed numerical algorithm was verified through a wind tunnel test, and the grid and timestep resolution analyses were conducted to ensure the reliability of the data. It was noted that the flow around the rail line was different under different infrastructure scenarios, especially in the case of the embankment, which degraded the aerodynamic performance of the train under the crosswind. The flow around the train on the flat ground and viaduct was different, although the aerodynamic performance of the train was similar in both cases. Moreover, the viaduct accidents were noted to have the most critical consequences, thereby requiring the most attention. The aerodynamic performance of the train on the windward track of the embankment under the crosswind was worse than that of the train on the leeward track. But for the other two infrastructure scenarios, the aerodynamic performance of the train on the windward track is relatively dangerous, which is mainly caused by the head car. These observations suggest that the aerodynamic behaviour of the train on an embankment under a crosswind must be carefully considered and that certain wind protection measures must be adopted around rail lines in windy areas.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.3
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• pp.270-276
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• 2014

Seasonal characteristics of water and sediment qualities and potential effects of the freshwater discharge from a small tide embankment interior in a coastal area in Goheung county were investigated from May to September in 2012. Chemical oxygen demand values (COD) were mostly higher than 2 mg/L in summer ebb tide, which exceed the standard value of water quality criteria II of acceptable level for aquaculture activities. Nitrogen and phosphorus were found as the limiting nutrients for algae growth in summer and fall and in spring, respectively. Nitrogen was the limiting nutrient for diatom growth in the whole studied period. The sudden high values of COD, ammonia, dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP) were found in water sample collected from station 5 which located in front of the tide embankment sluice gate during spring ebb tide. The freshwater discharge form the tide embankment interior maybe affected the survey areas during a short time interval. Mean values of eutrophication index of the surveyed coastal region in spring, summer and fall were all bigger than 1. Water quality was mostly considered at level II which acceptable for aquaculture activities. Sediment quality in this study was generally in the range of standard for fisheries environment.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1695-1704
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• 2008

The problems associated with constructing high-speed concrete track embankments over soft compressible soil has lead to the development and/or extensive use of many of the ground improvement techniques used today. Drains, surcharge loading, and geosynthetic reinforcement, have all been used to solve the settlement and embankment stability issues associated with construction on soft soils. However, when time constraints are critical to the success of the project, owners have resorted to another innovative approach. Especially, the design criteria of residual settlement is limited as 30mm for concrete track embankment, it is very difficult to satisfy this standard using the former construction method. Pile net method consist of vertical columns that are designed to transfer the load of the embankment through the soft compressible soil layer to a firm foundation and one or more layers of geosynthetic reinforcement placed between the top of the columns and the bottom of the embankment. This paper will present the guidelines for the design of pile net method to supported embankments. These guidelines were developed based on a review of current design methodologies and a parametric study of design variables using numerical modeling.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.1
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• pp.49-56
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• 1998

Ths study was peformed to evaluate the degree of degradation and safety of a small agricultural reservoir, Kosam Reservoir, in Kyungki Province. Evaluation was done by the program developed by the authors. Results of the study are as follows: 1) Although many burrows were found in downstream side of embankment and cracks were found in wall joining spillway, it appeared that degree of degradation of embankment was in good conditions. 2) Compressive strengths of concrete of crest, side channel, chute floor of spillway were in poor condition. But it appeared that overall degree of degradation of structures was in medium condition based on the criteria of the evaluation system 3) From the analysis of slope stability, safety factor of downstream slope was over 3.3 for the worst condition, such as flood and high water level and that of upstream slope was also over 3.6 for rapid drawdown. In case of earthquake, safety factors were over 2.5 for all conditions. Therefore embankment slopes of Kosam Reservoir were very stable for normal and earthquake condition. 4) As upon assumed failure of embankment of Kosam Reservoir, degree of damage was estimated to be very serious because of many loss of life and properties in the downstream area. 5) Overall grade of safety of Kosam Reservoir was in good condition. Therefore safety was considered to be "No problems" at the present time but further degradation may be proceeded partly and continuously as time goes by.e goes by.

• Journal of Korean Port Research
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• v.14 no.4
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• pp.463-473
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• 2000

Reinforcement with geotextiles have been used in the foundation soil to enhance the resistance of embankments to avoid failure through excessive deformation or shear in the foundation. It is improtant to know the amount of the strain and the displacement of buried geotextiles for the verification of the reinforcement behaviour. Full scale trial constructions were performed to check the deformational characteristics of the polyester(PET) mat which was used for the embankment reinforcement. Many instrumentation equipments including surface settlement plates, profile gauges and inclinometer casings were installed to observe the behaviour of the soft ground due to the soil embankment. 60 electrical resistance strain gauges and 9 vibrating wire LVDTs were installed 세 measure the deformation of the polyester mat. Results of various tests and geotextile, waterproofing and protection from the hazard environments were introduced. The proposed instrumentation method was effective for the monitoring or the geotextile behaviour. The direct attachment of electrical resistance strain gauges on the gertextile mat was able to measure small changes of the strain of geotextiles. At the end of the 5 month monitoring, 54 of 60 (93%) strain gauges and 7 of 9 (78%) displacement transducers survived all perils of the compaction impacts and the humidity. And the tensile strain of grotextiles increased as the ground displacement became larger. Though the observed strain of mats under the 3m high embankment load was less than 1%, the magnitudes of the strain according to the mat spreading method were different from each other.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1576-1580
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• 2006

The destruction of river and damage caused by flood are suddenly increasing due to the abnormal climate. In the investigation result about the damage, approximate 52% of the destruction of embankment are caused by earth work. Moreover, to recover conveyance of relief channel, bed sediment is dredged about 198 millions $m^3$ with 'the project of bed dredging'. So, the concern for bed sediment is the more increasing, the requiring high quality material for banking and the way for application of bed sediment are also the more increasing. In this paper, properties of bed sediment were analyzed through sedimentary mechanism analysis. Moreover, possibility to build embankment with bed sediment in 6 points which is in catchment of the Nak-dong river was also analyzed. At 6 points, which were selected to survey easily, sediment discharge was analyzed with formula. Moreover, size and permeability were analyzed and the feasibility for material of embankment was proposed. If bed sediment wasn't proper, complementary measures were proposed.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.3201-3207
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• 2011

This paper reviewed wave propagation of train vibration based on the study of high speed railway soft ground section with pile slab construction. In a filed of railway, concrete track has been adapted in a railway construction. And in order to maintain its track, soil improving method was required to control residual settlement. Within many soft ground settlement prevention techniques, pile slab method has an effect of minimizing residual settlement of soft ground. This is possible using support embankment load method by construct pile slab or cap the upper soft ground. This paper reviewed vibration wave characteristic of soft ground section with pile slab using numerical analysis application through finite element analysis. Pile slab method is established between high stiffened soft ground and embankment this creates a possibility of vibration block or slab amplification. Thus analyzed of wave propagation was done with roadbed and structure property to confirm application performance of pile slab method of high speed railway structure.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.2
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• pp.1-8
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• 2013

This study was performed for the purpose of analyzing the effect of tide on the stress-strain behavior in the boundary surface of sea dike embankment. Tide is a dynamic condition, but there are not suitable numerical models to solve the dynamic embankment condition caused by tide. So the analysis was simplified to quasi dynamic as follow. First, seepage by tide was analyzed according to elapsed time, and the results of the analysis at every hour during one periodic cycle time of 12 hours were applied to the pore water pressure conditions of stress-strain analysis with hyperbolic model by Duncan and Chang. The place at which maximum shear strain took place in the analysis result moved up and down repeatedly along the boundary of the dredged sand fill section and the crashed stone filter section. The value of maximum shear strain was large at high water level of tide. This result means that contraction and relaxation occur in turn repeatedly at every specific position along the boundary, and the repeated action compact loose position with sand moved down from the upper position by gravity. The experiment with the small sea dike model showed the result consistent with the numerical analysis. The surface of sea side on the dike collapsed at high water level after a couple of repetition of the rising and falling of water.

• Journal of the Korean Society for Railway
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• v.16 no.4
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• pp.278-285
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• 2013

The suppression of residual settlement is required on earthwork sections as concrete track is introduced. Use of pile-slab structure is one of the settlement restraining methods applied on soft ground. The slab distributes the upper embankment load and piles transfer the load from the slab to the stiff ground. While this method is very effective in terms of load transfer, it has not yet been established for dealing with the vibration transfer effects and interaction characteristics between a structure and the ground. It is possible that vibration caused by a moving train load is propagated in the upper embankment, because the slab acts as a reflection layer and waves are multi-reflected. In this present paper, wave propagation generated by a moving train load is evaluated in the time and frequency domains to consider a roadbed structure using an artificial impact load and field measured train load. The results confirmed the wave reflection effect on the pile-slab structure, if the embankment height is sufficient, vibration propagation can be stably restrained, whereas if the height is not sufficient, the vibration amplitude is increased.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1287-1296
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• 2007

Recently, the high speed railway comes into the spotlight as the important and convenient traffic infrastructure. In Korea, Kyung-Bu high speed train service began in about 400km section at 2004, and the Ho-Nam high speed railway will be constructed by 2017. The high speed train will run with a design maximum speed of 300-350km/hr. Since the trains are operated at high speed, the differential settlement of subgrade under the rail is able to cause a fatal disaster. Therefore, the differential settlement of the embankment must be controlled with the greatest care. Furthermore, the characteristics and causes of settlements which occurred under construction and post-construction should be investigated. A considerable number of studies have been conducted on the settlement of the natural ground over the past several decades. But little attention has been given to the compression settlement of the embankment. The long-term settlement of compacted fills embankments is greatly influenced by the post-construction wetting. This is called 'hydro collapse' or 'wetting collapse'. In spite of little study for this wetting collapse problem, it has been recognized that the compressibility of compacted sands, gravels and rockfills exhibit low compressibility at low pressures, but there can be significant compression at high pressures due to grain crushing by several researchers(Marachi et al. 1969, Nobari and Duncan 1972, Noorany et al. 1994, Houston et al. 1993, Wu 2004). The characteristics of compression of fill materials depend on a number of factors such as soil/rock type, as-compacted moisture, density, stress level and wetting condition. Because of the complexity of these factors, it is not easy to predict quantitatively the amount of compression without extensive tests. Therefore, in this research I carried out the wetting collapse tests, with focusing in various soil/rock type, stress levels, wetting condition more closely.