• 대한건축학회논문집:구조계
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• 제35권1호
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• pp.29-36
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• 2019

In the past, social insurance premiums, such as national pension and national health insurance, is contained within the costs of construction projects, have been lowered due to price competition of companies participating in the bidding. The government is implementing the "Ex-post settlement system" to improve the problem. Therefore, the purpose of this study is to examine the concept of an Ex-post settlement system and background of its introduction and to identify problems in the management of the system. The problems of the Ex-post settlement system are: 1) avoiding the participation of construction workers, 2) the rigidity of the insurance premium settlement method in construction field, and 3) the cause of direct construction cost reduction. The ways to improve these problems are: 1) excluding social insurance premiums from construction project cost, 2) securing flexibility of the settlement method of insurance premiums in construction field, and 3) expanding the scope of persons eligible to participate in social insurance.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.336-345
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• 2010

GS E&C was awarded the contract for the construction of Hanoi - Hai Phong Expressway Package EX-7 from Station Km 72+000 to Station Km 81+300 in December 2008. This project is the $7^{th}$ contract package of the 105.5 km long expressway near Hai Phong city, which includes a FCM-styled bridge along with high embankments over soft ground. For these high embankments, there is a need to treat the soft soil for improving the overall stability during construction and for reducing the post-construction settlement of the expressway. The Designer of this project had adopted four (4) different types of ground improvement techniques to treat the soft ground, including the prefabricated vertical drains (PVD), sand drains (SD), pack drains (PD, or sometimes called packed sand drains), and sand compaction piles (SCP). The main focus of soft soil treatment should be paid attention to the residual settlement after construction. In current design, however, it appeared that the secondary compression (or creep) of the improved soil layer and the consolidation settlement of the lower untreated compressible soil layer have been neglected in the estimation of the post-construction settlement. These uncalculated residual settlements may not only unsatisfy the design criteria but also raise serious problems during service period of this expressway. In this paper, the subsoil condition and current design were reviewed focusing on the employed soft soil treatment method and expected residual settlement.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2007년 가을학술발표회
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• pp.528-541
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• 2007

To get the possible for management and maintenance, it was analyzed the deformation characteristics, such as crest of embankment and concrete face slab, and leakage of concrete faced rockfill dams (CFRD). There are trends that embankment deformation depends on intact strength used rockfills rather than dam height, deformation normal to concrete face slab during the first reservoir filling is occurred more than 80% of the total deformation in general, and the magnitude and trend of concrete face slab deformation is similar to post-construction crest settlement. The results showed that the range of post-construction crest settlement suggested by Sherard and Cooke (1987), and Clements (1984) had a good agreement in the cases using rockfill with very high intact strength, but it had a trend which underestimated crest settlement in the cases using rockfill with medium to high intact strength. The maximum leakage rate in general was observed during the first reservoir filling and long-term leakage rate was rapidly increased when the dam height exceeds approximately 120m.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1268-1277
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• 2008

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'. This wetting collapse problem for the compressibility of compacted sands, gravels and rockfills, has been recognized by several researchers. For this wetting settlement problem, we showed the test results carried out with 4 fill materials. These tests were performed under the condition that the fill materials were inundated at the first wetting. Subsequently, in this study, we investigated the long-term settlement characteristics of the fill materials under the repeated partial wetting and rising of the ground water table happend by rainfall.

• 한국지반신소재학회논문집
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• 제8권2호
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• pp.31-39
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• 2009

본 연구에서는 준공 후 정부침하, 콘크리트 슬래브 변형, 누수량 등의 CFRD 거동 예측과 유지 관리 지표로 유용하게 활용될 수 있도록 하기 위해 국내외 27개의 콘크리트 표면차수벽형 석괴댐 (CFRD)의 사례를 분석하였다. 검토결과 Sherard와 Cooke(1987)과 Clements(1984) 등이 제안한 준공 후 정부침하 범위는 록필 재료의 강도가 매우 양호한 경우에는 적합하나, 보통에서 양호한 경우는 과소평가하는 경향이 있는 것으로 나타났다. 누수량 사례분석결과 CFRD에서 누수량의 주원인은 담수하중에 의한 슬래브의 변형이고, 최대 누수량은 주로 최초 담수중에 발생하고, 댐 높이가 125m보다 커지게 되면 누수량이 급증하는 경향이 있는 것으로 나타났다.

• Geomechanics and Engineering
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• 제11권6호
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• pp.847-865
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• 2016

In this study, a series of geotechnical centrifugal tests were conducted to investigate the effectiveness of settlement control of two types of rigid pile structure embankments (PRSE) in collapsible loess under high-speed railway embankments. The research results show that ground reinforcement is required to reduce the post-construction settlement and settlement rate of the embankments. The rigid pile structure embankments using rigid piles can substantially reduce the embankment settlement in the construction of embankments on collapsible loess, and the efficiency in settlement reduction is affected by the pile spacing. The pile-raft structure embankments (PRSE) have much stronger ability in terms of the effectiveness of settlement control, while the pile-geogrid structure embankments (PGSE) provides rapid construction as well as economic benefits. Rational range of pile spacing of PRSE and PGSE are suggested based on the requirements of various railways design speeds. Furthermore, the time effectiveness of negative skin friction of piles and the action of pile-cap setting are also investigated. The relevant measures for improving the bearing capacity and two parts of transition zone forms as positive control mean have been suggested.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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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.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 지반환경 및 준설매립에관한 학술세미나
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• pp.96-109
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• 2001

Land was reclaimed at the waterfront in the Pluit area of Jakarta for a 90ha residential-cum-recreational development. The reclamation works involve construction of permanent and temporary dykes, fill placement, soil improvement, dredging of internal canals and marina, and construction of canal revetment. The site lies on 16m to 18m thick soft seabed deposits. Settlement of the reclaimed areas will result as a consequence of consolidation of the soft underlying sediments. In order to reduce post-construction settlement to within acceptable levels, a system of vertical drains and preloading was adopted. This paper describes the use of Fibredrain, a prefabricated vertical drain made of jute and coir fibres developed at the National University of Singapore, in the soil improvement works and a secondary use in the construction of perimeter dykes for the reclamation works. The construction of the perimeter dyke must be carried out in such a way that slope stability is on ensured. Bamboo rafts and bamboo clusters with Fibredrain inserted, and stage construction were employed to improve stability during the dyke formation for the Pantai Mutiara project.

• Structural Engineering and Mechanics
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• 제66권1호
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• pp.15-25
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• 2018

Post-construction subgrade settlement especially differential settlement, has become a key issue in construction and operation of non-ballasted track on high-speed railway soil subgrade, which may also affect the dynamic performance of passing trains. To estimate the effect of differential subgrade settlement on the mechanical behaviors of the vehicle-slab track system, a detailed model considering nonlinear subgrade support and initial track state due to track self-weight is developed. Accordingly, analysis aiming at a typical high-speed vehicle coupled with a deteriorated slab track owing to differential subgrade settlement is carried out, in terms of two aspects: (i) determination of an initial mapping relationship between subgrade settlement and track deflections as well as contact state between track and subgrade based on a semi-analytical method; (ii) simulation of dynamic performance of the coupled system by employing a time integration approach. The investigation indicates that subgrade settlement results in additional track irregularity, and locally, the contact between the concrete track and the soil subgrade is prone to failure. Moreover, wheel-rail interaction is significantly exacerbated by the track degradation and abnormal responses occur as a result of the unsupported areas. Distributions of interlaminar contact forces in track system vary dramatically due to the combined effect of track deterioration and dynamic load. These may not only intensify the dynamic responses of the coupled system, but also have impacts on the long-term behavior of the track components.

• 한국지반신소재학회논문집
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• 제10권2호
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• pp.13-19
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• 2011

PC 암거는 터파기, 하부지반 처리, 암거 거치, 상호접합면에 누수방지용 패킹재 부착, PS 강선의 긴장을 통한 상호박스 접합, 되메우기 등의 일련의 과정으로 시공되어진다. 이 때 부적절한 하부지반 처리는 박스간 상호 부등침하를 야기할 수 있으며 결과적으로 지하수의 와류 및 내부유수의 누수를 발생시키게 된다. 본 연구에서는 하부지반이 연약한 경우 PC 암거 접합부의 부등침하를 저감하기 위하여 개발된 PC 기초판과 일체화된 암거의 거동을 현장 시험시공을 통해 분석하였다. 암거의 거동은 접합부에서 암거간의 벌어짐, 하부지반에 작용하는 토압 증가량, 암거 상부의 침하량 계측을 통해 분석되었으며, 분석결과로부터 PC 기초판과 일체화된 암거가 일반적인 시공방법인 PS 강선의 인장으로 체결된 암거에 비하여 침하 및 접합부에서 벌어짐이 적게 발생하는 것으로 나타났다.