• Geomechanics and Engineering
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• 제9권2호
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• pp.219-241
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• 2015

In this paper, a series of repeated load tests were carried out on a 150 mm diameter plate simulative of vehicle passes, to demonstrate the benefits of soil-rubber shred mixture in decreasing the soil surface settlement of road embankment. The results show that the efficiency of rubber reinforcement is significantly a function of the rubber content, thickness of rubber-soil mixture and soil cap thickness over the mixture. Minimum surface settlement is provided by 2.5% of rubber in rubber-soil mixture, the thickness of mixture layer and soil cap of 0.5 times the loading surface diameter, giving values of 0.32-0.68 times those obtained in the unreinforced system for low and high values of amplitude of repeated load. In this installation, in contrast with unreinforced bed that shows unstable response, the rate of enhancement in settlement decreases significantly as the number of loading cycles increase and system behaves resiliently without undergoing plastic deformation. The findings encourage the use of rubber shreds obtained from non-reusable tires as a viable material in road works.

• Geomechanics and Engineering
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• 제24권1호
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• pp.43-55
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• 2021

Peatland is distributed in China widely, and organic matters in soil frequently induce problems in the construction and maintenance of highway engineering due to the high permeability and compressibility. In this paper, a selected site of Dali-Lijiang expressway was surveyed in China. A numerical model was built to predict the settlement of the foundation of the selected section employing the soft soil creep (SSC) model in PLAXIS 8.2. The model was subsequently verified by the result of field observance. Consequently, the parameters of 17 types of soils from different regions in China with organic contents varying from 1.1-74.9% were assigned to the numerical model to study the settlement characteristics. The calculated results showed that the duration of primary consolidation and proportion of primary settlement in the total settlement decreased with increasing organic content. Two empirical equations, for total consolidation settlement and secondary settlement, were proposed using multiple linear regression based on the calculated results from the numerical models. The analysis results of the significances of certain soil parameters demonstrated that the natural compression index, secondary compression index, cohesion and friction angle have significant linear relevance with both the total settlement and secondary settlement, while the initial coefficient of permeability exerts significant influence on the secondary settlement only.

• 한국지반공학회논문집
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• 제25권5호
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• pp.17-28
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• 2009

연약지반상 성토시, 성토하중은 연약지반에 편재하중으로 작용하게 되어 기초 연약지반의 과도한 침하와 측방유동을 야기할 수 있다. 연약지반의 과도한 변형은 결국 성토체 자체와 인접 지반 및 구조물의 안전을 위협하게 된다. 연약지반의 변형거동에 영향을 미치는 요인은 크게 성토하중 조건과 지반조건으로 구분할 수 있다. 따라서 본 연구에서는 이들 조건을 달리한 5회의 모형실험을 수행하여, 성토하중 재하가 기초 연약지반의 변형거동에 미치는 영향을 평가하였다. 모형실험 결과, 성토하중 재하가 지중 측방변위 발생에 영향을 미치는 영향거리는 성토체 선단부로부터 재하폭의 2배까지인 것으로 나타났다. 또한 모형실험 결과를 근거로, 성토속도(v, kPa/day)와 일평균 침하량(${\Delta}s$, mm/day) 사이의 관계식과 성토속도와 일평균 지중 최대수평변위(${\Delta}y_m$, mm/day) 사이의 상관관계식을 제안하였다.

• 한국농공학회논문집
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• 제56권1호
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• pp.71-79
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• 2014

In this study, an experiment with large-scale model was performed according to raising the embankment in order to investigate the behavior of failure for embankment and spillway transitional zone due to overtopping. The pore water pressure, earth pressure, settlement and failure pattern by a rapid drawdown and overtopping were compared and analyzed. The pore water pressure and earth pressure at spillway transitional zone by overtopping increased a rapidly with the expansion of seepage erosion, but the crest showed a smally change due to effect of the inclined core type. And it is considered an useful data that can accurately estimate the possibility of failure of the reservoirs. A settlement at overtopping decreased a rapidly due to failure of crest. The relative settlement difference due to change of the water level at the upstream and downstream slope cause increase largely crack of crest. The behavior of failure by overtopping was gradually enlarged towards reservoirs crest from the bottom of the spillway transition zone, the inclined core after the raising the embankment was influenced significantly to prevent the seepage erosion.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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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.

• 한국지반환경공학회 논문집
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• 제8권5호
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• pp.31-38
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• 2007

현재 실무에서 사용되고 있는 샌드매트의 설계법에서는 주로 수평배수층의 배수거리, 침하속도, 투수성 등을 설계 인자로 사용하고 있으며, 현장 시공 시에는 성토체 하부에 동일한 두께로 시공하고 있다. 그러나 하부 연약지반의 변형에 따라 성토 중앙부와 양단에서 부등침하가 발생하게 되어 샌드매트 두께산정에 있어 과소평가될 가능성과 배수지연을 유발할 우려가 있음이 지적되어왔다. 본 연구에서는 연약지반의 변형으로 인해 생기는 부등침하의 발생이 배수지연 및 샌드매트의 두께산정에 어떠한 영향을 미칠 수 있는지 여부를 수치해석을 통해 분석하였다. 해석 결과 부등침하로 인하여 실질 유로두께의 감소를 확인할 수 있었으며, 새로운 위치수두의 차가 발생하여 배수지연 현상을 유발할 가능성이 있음이 확인되었다. 이에 대한 대응책으로 본 연구에서는 사전에 부등침하를 예측하여 성토 중앙부의 샌드매트 두께를 증가시킨 마운드형 샌드매트의 적용성에 대하여 검토하였으며, 압밀의 진행에 따라 변형이 크게 발생하여도 소정의 실질 유로두께를 유지하고 있음을 확인하였다. 특히, 마운드형 샌드매트는 연약지반 성토와 같이 변형의 분포가 위치에 따라 다른 경우의 건설공사에 매우 유효하리라 판단하며, 경제적이고 합리적인 수평배수재로서 적용이 가능할 것으로 판단되었다. 또한, 마운드형 샌드매트의 설계를 위해서는 성토단계별로 압밀속도, 배수거리나 투수성뿐만 아니라 연약지반의 침하특성을 정확하게 예측하는 것이 필수적이라고 사료된다.

• 한국농공학회지
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• 제38권6호
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• pp.35-41
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• 1996

The theory of consolidation has been achieved remarkable development in terms of theory such as finite consolidation theory, two dimensional Rendulic consolidation theory. Though those theories are well defined, the analysis is by no means straightforward, because associated properties are very difficult to determine in the laboratory, Therefore Terzaghi's one dimensional consolidation theory and Barron's cylindrical consolidation theory are still widely used in engineering practice. The theoretical shortcomings of those consolidation theories and uncertainties of associated properties make inevitably some discrepancy between theoretical and field settlements. Field settlement measurement by settlement plate is, therefore, widely used to overcome the discrepancy. Ultimate settlement is one of the most important factor of embankment construction on soft soils. Nowadays the ultimate settlement prediction methods using field settlement data are widely accepted as a helpful tool for field settlement analysis of embankment construction on soft soils. Among the various methods of ultimate settlement prediction, hyperbolic method and Asaoka's method are most commonly used because of their simplicity and ability to give a reasonable estimate of consolidation settlement. In this paper, the reliability of hyperbolic method and Asaoka's method has been examined using analytical methods. It is shown that both hyperbolic method and Asaoka's method are significantly affected by the direction of drainage.

• Geomechanics and Engineering
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• 제8권2호
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• pp.283-303
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• 2015

To research and analyze the differential settlements of foundations specifically, site investigations of existing railways and metro were firstly carried out. Then, the centrifugal test was used to observe differential settlements in different position between foundations on the basis of investigation. The theoretical model was established according to the stress diffusion method and Fourier method to establish an analytical solution of embankment differential settlement between different foundations. Finally, theoretical values and experimental values were analyzed comparatively. The research results show that both in horizontal and vertical directions, evident differential settlement exists in a limited area on both sides of the vertical interface between different foundations. The foundation with larger elastic modulus can transfer more additional stress and cause relatively less settlement. Differential settlement value decreases as the distance to vertical interface decreases. In the vertical direction of foundation, mass differential settlement also exists on both sides of the vertical interface and foundation with larger elastic modulus can transfer more additional stress. With the increase of relative modulus of different foundations, foundation with lower elastic modulus has larger settlement. Meanwhile, differential settlement is more obvious. The main error sources in theoretical and experimental values include: (a) different load form; (b) foundation characteristics differences; (c) modulus conversion; (d) effect of soil internal friction.

• 대한토목학회논문집
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• 제40권5호
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• pp.509-520
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• 2020

현행 내진설계 일반(KDS 17 10 00)에 따르면 내진설계 시 사용하는 입력지진파에 대한 기준이 명확히 제시되어 있고 실지진파에 대해서는 표준설계응답스펙트럼에 맞추어 보정하도록하고 있으나, 실지진파 선택에 따른 영향이 사전에 평가되지 않아 지진파 선택 시 어려움이 있다. 본 연구에서는 국내외에서 발생한 실지진파에 대하여 국내 설계기준이 제시하는 표준설계응답스펙트럼에 부합하도록 보정한 후, 수치해석을 통하여 필댐의 침하량 변화를 평가하였다. 그 결과 댐 하단에 작용하는 자유장 가속도의 영향보다 댐 마루에서의 최대가속도, 댐제체를 통한 증폭 특성등 제체 상부의 거동이 침하량에 가장 큰 영향을 미치는 것으로 나타났다. 또한, 동일한 표준설계응답스펙트럼으로 보정한 입력지진파일지라도 초기 실지진파와 댐 제체에서의 증폭 특성에 따라 침하량이 달리 평가될 수 있음을 확인하였다.

• 한국농공학회지
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• 제42권
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• pp.68-77
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• 2000

Analyses, in which load was regarded as instant load and gradual step load, respectively, were performed with data measured on a gradually loaded field, and the results were inspected to find the effect of load conditions, and the final settlements which were predicted by Hyperbolic, Tan's, Asaoka's, and Monden's methods were compared with each other. Settlement curves in which load was regarded as instant load and gradual step load being to coincide at twice the time of duration of embankment. On the ground installed vertical drain, from the results of Hyperbolic, Tan's, Asaoka's, Monden's, Curve fitting I, and Curve fitting II (simple, carrillo) methods it was concluded that Asaoka, Curve fitting I, and Curve fitting II methods are reliable for prediction final settlement with back analysis.