성토지지말뚝에 작용하는 연직하중에 대한 모형실험

홍원표,강승인 한국지반공학회 2000 한국지반공학회논문집 Vol.16 No.4

성토지지말뚝 상부의 성토지반내에서 발생되는 지반아칭효과에 의하여 성토하중이 말뚝에 전달되는 효과를 조사하면서 제안된 이론해석의 신뢰성을 확인하기 위하여 일련의 모형실험을 수행하였다. 본 모형실험에서 말뚝은 성토 아래에 일렬로 수열의 줄말뚝으로 설치하였으며, 말뚝캡보는 성토의 길이방향에 직각방향으로 말뚝두부에 설치하였다. 성토재의 하중전달에 가장 큰 영향을 미치는 요인으로는 말뚝캡보사이의 간격과 성토고를 들 수 있다. 이전의 이론적인 연구에 의해 제안된 지반아치의 반경보다 약 33%정도 큰 최소소요성토고보다 높게 성토를 실시할 경우 지반아치는 완벽하게 발생될 뿐만 아니라, 실험치와 이론치는 잘 일치함을 모형실험결과 확인할 수 있다. 모형말뚝캡보에 작용하는 성토하중의 분담률은 말뚝캡보사이의 간격이 증가함에 따라 감소하는 반면, 성토고가 높아짐에 따라 증가하였다. 따라서, 설계시 말뚝의 성토하중지지효과를 극대화시키기 위해서는 성토고를 충분히 높게한 상태에서 말뚝캡보의 간격비를 감소시켜야 한다. 여기서 말뚝캡보의 간격비를 감소시키려면 말뚝캡보사이의 간격을 감소시키거나 말뚝캡보의 폭을 증가시켜야 한다. A series of model tests were performed both to investigate the load transfer by soil acrching in fills above embankment pils and to verify of the theoretical analysis. In the model tests, the piles were installed in a row below the embankment and the cap beams were placed on the pile heads perpendicular to the longitudinal axias of the embankment. The space between pile cap beams and the embankment height was focused as the major factors affecting the load transfer in embankment fill. When the embankment fill was higher than the minimum required height, which was about 33% higher than the radius of the soil arch proposed by theoretical discussion in the previous study, not only the soil arching could be developed completely but also the experimental results showed good agreement with theoretical predictions. The portion of the embankment load carried by model pile cap beams decreased with increment of the space between pile cap beams, while it increased with increment of the embankment height. Therefore, to maximize the effect of embankment load transfer by piles on design, the interval ratio of pile cap beams should be decreased under considerably high embankments by reducing the space between cap beams and/or enlarging the width of pile cap beams.

차수매트 포설 범위에 따른 저수지 월류시 거동 특성

김영익,이익상,최돈환,임은상,김용성,Kim, Young-Ik,Lee, Ik-Sang,Choi, Don-Hwan,Im, Eun-Sang,Kim, Yong-Seong 한국농공학회 2010 한국농공학회논문집 Vol.52 No.2

This study was performed to develop the embankment protection method that can reduce demage by prevention of embankment loss and collapse from overflow due to heavy rain and flood. For overflow test, model dam was prepared and embankment behaviors were monitored with the established piezometer and strain meter during overflow. As a result of overflow test for model dam, in case of embankment without waterproof mat, the lower end of embankment was collapsed within 40 seconds after beginning of overflow. On the other hand, in case of embankment with waterproof mat, embankment collapse didn't occurred during overflow. Accordingly, establishment of waterproof mat for embankment showed that be absolutely effective for the embankment protection during overflow in reservoir. Also, it showed that the minimum establishment range of waterproof mat to prevent embankment collapse in reservoir is from maximum storage level to the lower end of embankment.

Mechanical Behavior of Reinforced Embankment with Different Recycling Waste Fillers

Lihua Li,Hongzhi Sheng,Henglin Xiao,Xinlong Zhou,Yiming Liu 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.8

The application of construction and demolition (C&D) waste and used tires in geotechnical engineering contributes to the demand of the sustainable development. This study mainly compared the mechanical behavior of pure sand embankment (PSE), C&D material embankment (CDME), sand-tire shreds mixture embankment (STSME) through a scale model test. Effects of tire shreds content, the first layer geocell reinforcement burial depth, geocell reinforcement depth and compaction degree on the bearing capacity of embankments were investigated. Moreover, embankment load-settlement ratio, the reinforced bearing capacity ratio, the bearing capacity improvement factor (IF), the embankment surface deformation, and the vertical earth pressure distribution inside the embankment were discussed. Results indicate that both C&D material fillers and sand-tire shreds mixture can improve the bearing capacity and stability of embankment slopes. However, C&D material is better than sand-tire shreds mixture in the improvement. The optimum value of tire shreds content is 5%. The reinforcement effect of geocell decreases with the increase of reinforcement depth. With the increase of the buried depth of the first layer, it first increases and then decreases. With the increase of compaction degree increases. The minimum earth pressure appears near the slope. The bearing capacity of CDME is greater than STSME. The ultimate bearing capacity of CDME under the action of the geocell is twice that of the unreinforced embankment.

취약대를 가진 모형제방의 침투거동에 관한 연구

박민철(Mincheol Park),임은상(Eunsang Im),이석영(Seokyoung Lee),한희수(Heuisoo Han) 한국지반환경공학회 2016 한국지반환경공학회논문집 Vol.17 No.7

본 연구는 투수계수가 큰 취약대가 제방에 존재할 경우의 침투거동에 관한 것이다. 침하계, 간극수압계, 수직 토압계 및 FDR 센서로 구성된 지점형 센서와 분포형 TDR 센서를 이용하여 제방의 침투특성 및 제방거동을 계측하였다. 계측결과들은 2차원 및 3차원 수치해석결과들과 비교・분석되었다. 모형제방은 길이 7m, 폭 5m, 높이 1.5m의 크기이며 제외지 수위는 1.3m인 세립질 모래로 조성된 제방이다. 계측 및 수치해석의 침투거동이 거의 유사하여 적절한 계측시스템으로 제방의 안정성을 실시간 모니터링 할 수 있음을 알 수 있었다. 수치해석의 경우 정상단면에서는 2차원 및 3차원 해석결과가 거의 동일하나, 취약단면을 고려할 경우 2차원 해석의 침윤선이 3차원 결과보다 빠르게 진행된 후 두 결과가 수렴되었다. This research is focused on the seepage behavior of embankment which had the weak zone with big permeability. The distributed TDR (Time Domain Reflectometer) and point sensors such as settlement gauge, pore water pressuremeter, vertical total stressmeter, and FDR (Frequency Domain Reflectometer) sensor were used to measure the seepage characteristics and embankment behavior. Also, the measured data were compared to the data of 2-D and 3-D numerical analysis. The dimension of model embankment was 7 m length, 5 m width and 1.5 m height, which is composed of fine-grained sands and the water level of embankment was 1.3 m height. The seepage behavior of measuring and numerical analysis were very similar, it means that the proper sensing system can monitor the real-time safety of embankment. The result by 2-D and 3-D numerical analysis showed similar saturation processing, however in case of weak zone, the phreatic lines of 2-D showed faster movement than that of 3-D analysis, and finally they converged.

제방붕괴에 관한 수리학적 연구

김진홍 중앙대학교 건설환경연구소 2001 環境科學硏究 Vol.12 No.1

Theoretical analyses on the embankment failure and the comparisons with the experimental results were presented. Flushing process of the sand embankment and its failure due to overflow was analyzed by the concept of the dilatant model which is based on the grain-inertia regime. Hydraulic model test in the movable bed conditions was carried out to investigate the flushing process of the sand embankment. The velocity profile was obtained using the stress-strain relationship. It was applied to any type of velocity profiles in the fluid-granule mixed flow, which showed a considerable improvement for the existing theories on a debris flow. The erosion depth was obtained using the dynamic Coulomb criterion, where the erosion occurs to the depth level until the driving force becomes equal to the resisting force. For a design purpose, formulas and figure diagrams for obtaining a velocity profile, and erosion depth, and overflow depth and a granular discharge were proposed for given values of a flood discharge, particle properties and embankment scale.

말뚝으로 지지된 성토지반 내 펀칭전단파괴

홍원표,송제상,홍성원 한국지반공학회 2010 한국지반공학회논문집 Vol.26 No.3

The mechanism of load transfer by punching shear in pile-supported embankments is investigated. Based on the geometric configuration of the punching shear observed in sand fills on soft ground, a theoretical analysis is carried out to predict the embankment loads transferred on a cap beam according to punching shear developed in pile-supported embankments. The equation presented by the theoretical analysis was able to consider the effect of various factors affecting the vertical loads transferred on the cap beam. The reliability of the presented theoretical equation is investigated by comparing it with the results of a series of model tests. The model tests were performed on cap beams, which had two types of width; one is narrow width and the other is wide width. Sand filling was performed through seven steps. Two types of loading pattern were applied at each filling step; one is the long-term loading, in which sand fills at each filling step were kept for 24 hours, the other is the short-term loading, in which sand fills at each filling step were kept for 2 hours. The vertical loads measured in all model tests show good agreement with the ones predicted by the theoretical equation. Finally, the predicted vertical loads also show good agreement with the vertical loads measured in a well-instrumented pile-supported embankment in field, where cap beams were placed on too wide space.

Centrifuge Modeling of Embankment Failure due to Underground Cavity and Its Electrical Resistivity Monitoring

조형익,이명종,방은석,김동수 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.10

In this paper, embankment or levee failure due to the interaction between a cavity within an embankment body and high water level was simulated in a centrifuge test and monitored by electrical resistivity tomography (ERT) survey technique. As the centrifuge modeling is an effective research tool for levee stability analysis and the ERT survey is generally adopted in field for health monitoring of levee, physical modeling of levee stability problem and its monitoring by the ERT survey in the centrifuge provides a great opportunity for researchers. Initially, 1 g preliminary test was performed for simulating the underground cavity using a buried ice block to ensure the simulation of such cavity in the centrifuge model. Subsequently, 20 g centrifuge test was performed. At the 20 g-level, over the three stages’ water level in river side was maintained to simulate expansion of the underground cavity with increase in groundwater level. Continuous ERT survey was simultaneously conducted to monitor the variation of internal state of the embankment body. During the final high water level, subsidence of levee surface occurred at the vertical location on top of the cavity which can lead to embankment failure. The ERT results (two dimensional contour plots) from the centrifuge test correspond well to the expected process of levee subsidence caused by upward development of inner cavity by showing definite resistivity difference between the cavity and adjacent soil. From the centrifuge test, it is concluded that the cavity within the embankment body could induce failure upon interacting with the high water level, and the ERT monitoring could effectively capture the geotechnical process which shows the upward development of underground cavity.

Embedded type new in-situ soil stiffness assessment and monitoring technique

Junghee Park,Namsun Kim,Jong-Sub Lee,Younggeun Yoo,Jin Wook Kim 국제구조공학회 2024 Smart Structures and Systems, An International Jou Vol.34 No.1

We aimed to assess the evolution of small-strain stiffness and relative density in non-compacted embankment layers. We developed embedded type in-situ soil stiffness measurement devices for monitoring small-strain stiffness occurring after filling at a test site and conducted comprehensive laboratory compaction tests using an oedometer cell with a bender element. However, direct comparison is extremely difficult because the shear wave velocity measured in the field and laboratory depend on depth and effective stress, respectively. Therefore, we propose a method for establishing a relationship between effective stress and depth using a compressibility model. In this study, the shear wave velocity measured in the field was compared to the estimated shear wave velocity-depth profiles for completely dry and saturated conditions with different relative densities. The relative density under saturated soil conditions may vary between 50% and 90% and tends to be closer to 95%. Under dry soil conditions, the relative density of the embankment can vary from 30% to 70% and tends to approach 76%. For model validation, the relative density estimated from shear wave velocity-depth profiles was compared to that estimated from DCPI data. In other words, the results analyzed in the context of an effective stress-depth model enable the prediction of engineering properties such as the small-strain stiffness and relative density of embankment layers. This study demonstrates that physics-based data analyses successfully capture the relative density of non-compacted embankment layers.

An analytical model of the additional confining stress in a prestress-reinforced embankment

Xinyu Ye,Fangxu Li,Wuming Leng,Xi Ai,Hossein Moayedi,Qishu Zhang 국제구조공학회 2023 Smart Structures and Systems, An International Jou Vol.31 No.5

Using a device composed of two lateral pressure plates (LPPs) and a steel reinforcement bar to apply horizontal pressure on slope surfaces, a newly developed prestress-reinforced embankment (PRE) is proposed, to which can be adopted in strengthening railway subgrades. In this study, an analytical model, which is available of calculating additional confining stress (<i>σ</i>_H) at any point in a PRE, was established based on the theory of elasticity. In addition, to verify the proposed analytical model, three dimensional (3D) finite element analyses were conducted and the feasibility in application was also identified and discussed. In order to study the performance of the PRE, the propagation of <i>σ</i>_H in a PRE was analyzed and discussed based on the analytical model. For the aim of convenience in application, calculation charts were developed in terms of three dimensionless parameters, and they can be used to accurately and efficiently predict the <i>σ</i>_H in a PRE regardless of the embankment slope ratio and LPP side length ratio. Finally, the potential applications of the proposed analytical model were discussed.

성토로 인한 연약지반의 측방유동 거동에 관한 실내모형실험

유승경(You Seung-Kyong),김재홍(Kim Jae-Hong) 한국토목섬유학회 2011 한국지반신소재학회 논문집 Vol.10 No.1

연약 점성토 지반에 성토를 할 경우 과도한 침하와 측방유동으로 인한 피해를 최소화하기 위해 토목섬유/성토지지말뚝공법이 주로 사용되고 있다. 본 공법은 연악지반 층을 관통하여 지지층에 관입시킴으로써 상재하중을 지지하게 하여 상재하중으로 인한 침하와 측방유동 발생을 최소화한다. 본 연구에서는 연약 점성토 지반에 설치된 토목섬유/성토지지말뚝공법의 보강효과를 정량적으로 검토함을 목적으로 하였다. 실내모형실험을 통하여 무보강 및 성토지지말뚝 보강의 경우에 대한 지반 거동을 재현하고 성토지지말뚝에 의한 측방유동 억지효과를 분석하였다. 이때 성토지지말뚝을 설치한 경우에 대해서는 상재하중의 크기를 다르게 설정하여 완속 재하와 급속 재하의 경우에 대한 측방유동의 억지효과를 분석하였다. Pile-supported embankment is one of the reinforcing methods to minimize damage due to the severe subsidence and lateral now when soft clay ground is supported with embankment. pile-supported embankment mainly penetrates soft ground into the bearing stratum in order to support surcharge load which minimizes the subsidence and lateral now due to the surcharge load. The aim of this research is to review quantitatively reinforcing effect of pile-supported embankment which is installed in soft clay ground. From the model test, it reproduced the ground movement with regard to the non-reinforced and reinforcing embankment-pile and also analyzed stabilizing effects of lateral flow due to the pile-supported embankment. With regard to the case of installing pile-supported embankment, its were analyzed stabilizing effects of lateral now in cases of quick-load and slow-load to make different surcharge load.