• Title/Summary/Keyword: 즉시침하

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The Immediate Settlement Estimation of the Improved Soft Ground Using Bamboo Mats (대나무매트로 보강된 연약지반의 즉시침하량 추정에 관한 고찰)

  • Kim, Woo-Jin;Kim, Yoon-Ha;Kang, Jin-Tae;Choi, Yong-Hwan;Kim, Jong-Ryeol
    • Journal of the Korean Geotechnical Society
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    • v.24 no.5
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    • pp.55-64
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    • 2008
  • When the structure is constructed on the soft ground, the embankment is settleed into the soft ground. At this time, the settlement of the structure is needed to predict. We are using bamboo mats construction only as a way of test construction. Under this circumstance, using the equation of Janbu and Perloff, we calculated the settlement, and analyzed the problem, suggesting proper theoretical equations showing the settlement of soft ground using bamboo mat. Using this equations the settlement was calculated and compared with the result of FEM. The result of the application was very close to the numerical value and the trend of theoretical equations. Using the existing equations, the settlement in Janbu's and Perloff's methods were calculated to be 40% of the actual settlement.

Settlement of Fine Recycled-concrete Aggregates Foundation under Sewage Conduit System (폐콘크리트 재생잔골재의 하수관거 모래기초 적용에 따른 침하 거동)

  • Oh, Je-Ill;Ahn, Nam-Kyu;Lee, Ju-Young
    • Journal of Korean Society of Environmental Engineers
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    • v.27 no.5
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    • pp.486-490
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    • 2005
  • Fine recycled-concrete aggregates(RCAs) instead of natural sand were tested for a foundation material under sewage conduit system, which was evaluated based on foundation settlement at various conditions. To obtain this applicability of RCAs, the settlement behavior was simulated with FLAC program based on the difference of material properties, and immediate settlement behaviors and the change of material properties under the simulated drainage conditions also tested at the various loading conditions in the laboratory. Finally, large-scale settlement test in the field was conducted to prove the above feasibilities. Subsequently, the amount of settlement from the FLAC simulation was calculated under $5.0{\times}10^{-6}\;m$ and the extent of settlement and property changes (porosity, permeability and waster absorption) was not noticeable from the laboratory experiments. Also, settlement monitoring from the field experiment showed the consistent results with laboratory experiments except for the consolidation settlement(=5 mm) of the round below the foundation. In summary, adopting fine RCAs as a foundation material for sewage conduit system was resonable based of geotechnical point of view.

An Experimental Study for Estimation of Compression Settlement on Embankment Material Under Self-weight (성토체 압축침하량 산정에 관한 연구)

  • Kwon, Jeongeun;Noh, Ilkwon;Jung, Juyoung;Im, Jongchul
    • Journal of the Korean GEO-environmental Society
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    • v.10 no.4
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    • pp.33-40
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    • 2009
  • In earthwork projects, the designer considers cut and fill balance for minimizing earthwork which may significantly decrease construction costs. Despite carrying out considerable earthwork design, the decrease in volume of earth occurs in construction sites because of embankment settlement under self-weight, consolidation settlement of soft ground, cavity filling and soil loss due to rainfall-runoff. To reflect the decrease in volume of earth, the specifications for road construction just give shrinkage factors in embankment for soils without consideration of embankment settlement under self-weight. In this study, the computational method is used to estimate the amount of embankment settlement under self-weight developed by Iseda (1972) and Ishii (1976). This research shows that the total compression settlements are between 3 to 10 percent of embankment height according to the property of embankment material and embankment height. As a result, the designer should consider the compression settlement on embankment material under selt-weight.

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Design of Rigid Sewer Pipe by Bearing Capacity and Settlement (지지력과 침하량을 고려한 강성관용 하수관거 설계)

  • Kim, Seong-Kyum;Oh, Seung-Sik;Lee, Kwan-Ho
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.6
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    • pp.137-143
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    • 2020
  • This study proposes an improvement plan for the evaluation of the bearing capacity and settlement of sewer pipe bases for the improvement of design methods for determining pipe breakage. Under the same conditions, the safety of crushed stone foundation was the lowest. Concrete VR pipe and prefabricated plastic foundations were found to be safe at most excavation depths. The bearing capacity of a rigid pipe foundation was determined by the shape of the foundation, soil conditions, and groundwater, irrespective of the type of foundation. As the depth of the excavation increases, the settlement tends to decrease immediately, and as the diameter of the pipe increases, the settlement tends to increase immediately at the same depth. It is thus reasonable to consider the bearing capacity and the instant settlement amount to solve the problems caused by the settlement of a rigid sewer pipe.

Prediction of Settlement of SCP Composite Ground using Genetic Algorithm (유전자 알고리즘 기법에 근거한 SCP 복합지반의 침하 예측)

  • 박현일;김윤태;이형주
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.16 no.2
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    • pp.64-74
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    • 2004
  • In order to accelerate the rate of consolidation settlement, to reduce settlement, and to increase bearing capacity for soft ground under quay wall, sand compaction pile method (SCP) has widely been applied. Improved ground is composite ground which is consisted of the sand pile-surrounding clayey soil. As caisson and upper structures are installed on SCP composite ground, the settlement is compositively occurred by elastic compression of sand compaction piles and also consolidation of the surrounding clay ground. In this study, the combined settlement model is proposed to predict the settlement of SCP composite ground in basis of elastic theory for sand compaction pile and consolidation theory for marine soft clay. Optimization technique was performed based on back-analysis so that real coded genetic algorithm was applied to estimate the parameters of the proposed settlement model. Case analysis was carried out for a domestic SCP composite ground to examine the applicability of the proposed prediction technique.

Evaluation of Mechanical Characteristics and Concentration Target Layer Applicability of Silty Sand by Fines Content (실트질 모래의 세립분 함유율에 따른 역학적 특성 및 압밀 대상층 적용성 평가)

  • Jung-Meyon Kim;Min-Seo Kang;Jong-Joo Kim;Seung-Joo Lee;Young-Seok Kim;Chan-Young, Park;Yong-Seong, Kim
    • Journal of the Korean Geosynthetics Society
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    • v.22 no.3
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    • pp.37-46
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    • 2023
  • In this paper, the physical properties, stress deformation and strength characteristics, density and permeability characteristics of silty sand (SM) by fines content were analyzed through indoor tests. also based on the results of the indoor tests, a compact analysis was performed according to the content of SM, and the applicability of SM ground to the compacted target layer was evaluated by comparing it with the measurement data of the actual problem site. As a result of indoor tests and compression analysis, SM changed its mechanical properties from sandy soil to viscous soil when the fine particle content was 35% or higher, and using field measurement data, SM was found to have a higher compression tendency than direct subsidence. Therefore, the mechanical characteristics of SM above Fc 35% are considered to be similar to that of viscous soil, which is different from the compression characteristics of the tendency of immediate subsidence to conventional sandy soil, so it is necessary to present the mechanical characteristics of SM through further research. The research findings highlight the importance of considering consolidation settlement in silty sand (SM) when evaluating soft soil conditions. These findings can aid in revising criteria for assessing weak ground conditions by providing essential engineering property data based on varying fines content in silty sand.

Behavior Analysis of Particle Crushing about Sabkha Layer under Hydrotest (Sabkha층의 Hydrotest 시 입자파쇄 거동분석)

  • Kim, Seokju;Han, Heuisoo
    • Journal of the Korean GEO-environmental Society
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    • v.14 no.9
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    • pp.57-65
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    • 2013
  • Carbonate sands can be crushed under low confining pressure to achieve high compressibility. So particle crushing has significant influence on characteristics of strength and deformation. Trial embankment and hydrotest are conducted on Sabkha layer, consisting of carbonate sand to build tank structure. In this paper the settlement behavior was analyzed from each test. Particle crushing happened from 80 to 170kPa stress under compression test, and calcium was detected from chemical test. The test result came out Sabkha soil was very weak and easy to be crushing. About trial embankment test, particle crushing was not happen, and then extinction of pore water pressure and settlements were finished just during 2 days. On the other hand, the long-term settlement was happened in hydrotest. So the two test results did not correspond to each other. If loading stress is higher than yielding stress, instant settlement and secondary compression settlement are happened as a result of the particle crushing.

A Deformation Prediction of the Embankment on the Soft Clayey Foundation - A Case Study of the Sea Dike of Koheung Bay - (점성토지반에 축조한 제방의 변형추정 -고흥만 방수제 사례연구를 중심으로-)

  • 오재화;이문수
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.40 no.4
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    • pp.94-102
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    • 1998
  • This paper aims at developing the prediction technique of the deformation for the embankment such as sea dike and shore protection relevant to reclamation project along the southern coast of the Korean Peninsula. Generally total deformation of a sea dike over clayey foundation are composed of immediate settlement, plastic deformation and consolidation settlement. Plastic deformation occurs when the ultimate bearing capacity is less than overburden pressure containing the stress increment due to the construction of an embankment. The reliable prediction of total settlement is very important since deformed final geometry of sea dike is directly connected for analysing the safety of the long-term slope failure and piping. During this study, plastic deformation, major part of deformation was analysed using the program developed by authors, whereas immediate settlement and consolidation settlement were predicted by Mochinaka and Sena's method and Terzaghi's 1-dimensional theory of consolidation respectively. In order to validate the prediction technique for the deformation, a case study of Koheung Bay reclamation works was carried out. A good agreement was obtained between observation and prediction, which means the applicability of the technique.

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Lesson and proposal of revised equations from the Pan method application case for soft clay improvement (PBD 공법 시공사례를 통한 교훈 및 개선안 제안)

  • 유한구;조영묵;김종석;박정규
    • Proceedings of the Korean Geotechical Society Conference
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    • 2001.10a
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    • pp.147-158
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    • 2001
  • In general, two methods have been used to predict settlement of soft ground. One method is Terzaghi's one dimensional consolidation theory which gives time-settlement relationship using the standard consolidation test results. The other is forecasting method of ground settlement to be occured in the future using in-situ monitoring data. The above both methods have some defects in application manner or in itself especially in very deep and soft clayey ground. In view of the lessons and experiences of soft ground improvement projects, several techniques were proposed for more accurate theorectical calculation of consolidation settlement as follows ; ① Subdivision of soft ground, ② Consideration of secondary compression, ③ Using the modified compression index, etc. And also, revised hyperbolic fitting method was suggested to minimize the error of predicted future settlement. In addition, revised De-Beer equation of immediate settlement of loose sandy soil was proposed to overcome the tendency to show too small settlement calculation results by original De-Deer equation. And also, considering the various effects of settlement delay in the improved ground by vertical drains, time-settlement caculation equation(Onoue method) was revised to match the tendency of settlement delay by using the characteristics of discharge capacity decreases of vertical drain with time elapse by the pattern of hyperbolic equation.

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Critical face pressure and backfill pressure of shield TBM considering surface settlements of saturated clayey ground (쉴드 TBM 굴진에 따른 포화 점성토 지반의 침하거동을 고려한 한계 굴진면압과 한계 뒤채움압)

  • Kim, Kiseok;Oh, Ju-Young;Lee, Hyobum;Choi, Hangseok
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.2
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    • pp.433-452
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    • 2018
  • The shield tunneling method can minimize surface settlements by preventing the deformation of tunnel face and tunnel intrados due to tunnel excavation. For this purpose, it is very important to control the operating conditions of shield TBM. The face pressure and backfill pressure for tail void grouting should be the most important and immediate measure not only to restrain surface settlement, but also to influence the effective stress and pore water pressure around the circumstance of tunnel during excavation. The reaction of the ground to the application of face pressure and backfill pressure relies on the stiffness and permeability of ground. Especially, the reaction of saturated clayey ground formations, which shows the time-dependent deformation, is different from the permeable ground. Hence, in this paper it was investigated how the TBM operating conditions, ground stiffness, and permeability impact on the surface settlement of saturated clayey ground. For this purpose, a series of parametric studies were carried out by means of the stress-pore water pressure coupled FE analysis. The results show that the settlement of soft clayey ground is divided into the immediate settlement and consolidation settlement. Especially, the consolidation settlement depends on the ground stiffness and permeability. In addition, the existence of critical face pressure and backfill pressure was identified. The face pressure and backfill pressure above the critical value may cause an unexpected increase in the ground settlement.