• 제목/요약/키워드: Soil Resistance Force

검색결과 107건 처리시간 0.022초

조류 흐름을 고려한 해양지반 수리저항성능 실험기 개발 (Development of Apparatus for Measuring Hydraulic Resistance of Sea Ground Considering Tidal Current Flow)

  • 강경오;정현철;김영상
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2010년도 추계 학술발표회
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    • pp.1366-1369
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    • 2010
  • Along with the increasing need of sea development, the hydraulic stability of seabed structure on a soft seafloor ground is becoming an issue in the course of seaside development recently. However, the movement and hydraulic resistance or hydraulic stability of seafloor ground are mutually coupled with various phenomena, and there has been no clear proof for the issue, which makes it difficult to forecast. Furthermore, most researches are focused on hydraulic variables and the conditions of marine external force, while there have been few researches into the assessment in consideration of the type of a seafloor ground and the geotechnical characteristics. In addition, according to the periodic change of the flow direction, possible changes in hydraulic resistance performance of the seafloor deserves all the recognition. But there is no way to measure the hydraulic unstability of the sea ground due to tidal flow quantitatively. In this study, conventional hydraulic resistance measurement apparatus was improved to consider direction change of the current flow. Various artificial clayey soil specimens were made from Kaolinite and Jumunjin standard sand and hydraulic resistance tests were performed by changing the flow direction to validate the effect of the direction change on the scour of the seafloor.

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강체차륜(剛體車輪)의 견인력(牽引力) 추정(推定) 모형(模型) (Traction Model of Rigid Wheels)

  • 조병용;김경욱
    • Journal of Biosystems Engineering
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    • 제14권3호
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    • pp.151-157
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    • 1989
  • A mathematical model was developed to predict traction forces of rigid wheels. The modeling was based on the energy principle that the total energy delivered to a driving wheel is equal to the works done by the useful traction force and motion resistance of that wheel. The effect of the wheel slippage was also included in the modeling. Verification of the proposed model was provided by comparing the tractive coefficients predicted by the model to those obtained experimentally at the in-door soil bin tests. The model predictions were found to be a reasonable agreement with the experimental results.

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부유식 해상구조물의 계류를 위한 사질토 지반의 석션파일 설계 (Design for Installation of Suction Piles in Sand Deposits for Mooring of Floating Offshore Structures)

  • 박철수;이주형;백두현;도진웅
    • 한국지반공학회논문집
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    • 제30권10호
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    • pp.33-44
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    • 2014
  • 본 연구에서는 국내 서남해 해상지역 시범사업의 부유식 콘크리트 해상구조물 계류를 위한 기초시스템으로서 석션파일을 적용하기 위한 예비설계를 수행하였다. 설계에 앞서 시범사업 대상지역인 서남해안에 대한 지반 및 수리 조건, 재현주기 100년의 환경외력 등 현장 조건을 면밀히 검토하였다. 석션파일은 설계하중에 대한 수평방향 지지력을 만족해야하고, 뿐만 아니라 지반종류 및 강도정수, 유효응력, 침투압 등의 조건에 따른 관입성 검토가 수행되어야 한다. 본 설계에서는 석션파일 직경에 따라 설계외력에 대해 수평방향 안정성을 확보할 수 있는 목표 침설깊이를 설정하고, 침설단계별로 상한석션압 이내에서 관입력과 관입저항력 비교를 통해 설계석션압을 산정하였다. 검토결과 직경 3.0~5.0m 석션파일의 경우 목표 깊이까지 침설이 불가능하였고, 직경 6.0m와 7.0m 석션파일은 각각 침설깊이 8.5m와 8.0m에서 수평방향 안정성 및 설계석션압에 의한 침설을 모두 만족함을 확인하였다.

The effect of base isolation and tuned mass dampers on the seismic response of RC high-rise buildings considering soil-structure interaction

  • Kontoni, Denise-Penelope N.;Farghaly, Ahmed Abdelraheem
    • Earthquakes and Structures
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    • 제17권4호
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    • pp.425-434
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    • 2019
  • The most effective passive vibration control and seismic resistance options in a reinforced concrete (RC) high-rise building (HRB) are the base isolation and the tuned mass damper (TMD) system. Many options, which may be suitable or not for different soil types, with different types of bearing systems, like rubber isolator, friction pendulum isolator and tension/compression isolator, are investigated to resist the base straining actions under five different earthquakes. TMD resists the seismic response, as a control system, by reducing top displacement or the total movement of the structure. Base isolation and TMDs work under seismic load in a different way, so the combination between base isolation and TMDs will reduce the harmful effect of the earthquakes in an effective and systematic way. In this paper, a comprehensive study of the combination of TMDs with three different base-isolator types for three different soil types and under five different earthquakes is conducted. The seismic response results under five different earthquakes of the studied nine RC HRB models (depicted by the top displacement, base shear force and base bending moment) are compared to show the most suitable hybrid passive vibration control system for three different soil types.

결합강그리드보강재의 특성 및 적용 (Charateristics of the Jointed Steel-Grid Reinforcement and the Application)

  • 한중근
    • 한국환경복원기술학회지
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    • 제5권3호
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    • pp.15-22
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    • 2002
  • To analysis of the embanked slope stability using a jointed reinforcement, the internal stability and the external stability have to be satisfied, respectively. But, because the lengths of ready-made steel-grid were limited, the reinforcements must be connecting themselves to the reinforcing. In this study, the mechanical test was carried out to investigate the tensile failure and the pullout failure at the joint parts of them, which was based on the analysis of reinforced slope in field. Through the tensile tests in mid-air for the jointed steel-grid, the deformation behavior was seriously observed as follows : deformation of longitudinal member, plastic deformation of longitudinal member and of crank part. Those effects were due to the confining pressure and overburden pressure of the surrounding ground. The bearing resistance at jointed part of jointed steel-grid was due to the latter only. The maximum tensile forces were higher about 20kN~27kN than ultimate pullout resistance, but, the results of those was almost the same in mid-soil. The failures of steel-grid occurred at welded point both of longitudinal members and transverse members and of jointed parts. The strength of jointed parts itself got pullout force about 20kN, which was about 65% for ultimate pullout force of the longitudinal members N=2. To the stability analysis of reinforced structure including the reinforced slope, the studying of connection effects at jointed part of reinforcement members must be considered. Through the results of them, the stability of reinforced structures should be satisfied.

Growth and yield responses of rice varieties to various soil water deficit conditions under different soil types

  • Kikuta, Mayumi;Samejima, Hiroaki;Magoti, Rahab;Kimani, John M.;Yamauchi, Akira;Makihara, Daigo
    • 한국작물학회:학술대회논문집
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    • 한국작물학회 2017년도 9th Asian Crop Science Association conference
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    • pp.322-322
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    • 2017
  • To avoid drought stress under rainfed upland conditions, it is important for rice to efficiently utilize water at shallow soil layers supplied by rainfall, and access to water retained in deer soil layers. The root developmental characteristics of rice, which play important role in the adaptability to drought conditions, vary depending on the variety. Moreover, water availability for plant differs depending on the soil types that have different physical properties such as water holding capacity, permeability, capillary force, penetration resistance, etc. In this study, we evaluated growth and yield responses of rice varieties to various soil water deficit conditions under three different soil types. The experiment was conducted in a plastic greenhouse at the Kenya Agricultural and Livestock Research Organization-Mwea from October 2016 to January 2017. Two upland varieties (NERICA 1 and 4) and one lowland variety (Komboka) were grown in handmade PVC pots (15.2 cm diameter and 85.0 cm height) filled with three different types of soil collected from major rice-growing areas of the country, namely black cotton (BC), red clay (RC), and sandy clay (SC). Three watering methods, 1) supplying water only from the soil surface (W1), 2) supplying water only from the bottom of the pots (W2), and 3) supplying water both from the soil surface and the bottom of pots (W3), were imposed from 40 days after sowing to maturity. Soil water content (SWC) at 20, 40, and 60 cm depths was measured regularly. At the harvesting stage, aboveground and root samples were collected to determine total dry weight (TDW), grain yield, and root length at 0-20, 20-40, 40-60, and 60-80 cm soil layers. Irrespective of the watering methods, the greatest root development was obtained in RC, while that in BC was less than other two soils. In BC, the degree of yield reduction under W1 was less than that in RC and SC, which could be attributed to the higher water holding capacity of BC. In RC, the growth and yield reduction observed in all varieties under W1 was attributed to the severe drought stress. On the other hand, under W2, SWC at the shallow soil depth in RC was maintained because of its higher capillary force compared with BC and SC. As the result, growths and yields in RC were not suppressed under W2. In SC, deep root development was not promoted by W2 irrespective of the varieties, which resulted in significant yield losses. Under W1, the rice growth and yield in SC was decreased although shallow root development was enhanced, and the stomatal conductance was maintained higher than RC. It was suspected that W1 caused nutrients leaching in SC because of its higher permeability. Under rainfed conditions, growth and yield of rice can be strongly affected by soil types because dynamics of soil water conditions change according to soil physical properties.

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원심모형실험을 이용한 모래지반에 관입된 계류선 거동 평가 (Evaluation of Behaviors on Mooring Line Embedded in Sand Using Centrifuge Test)

  • 이훈용;김수린;김재현;김동수;추연욱;권오순
    • 한국해양공학회지
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    • 제28권1호
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    • pp.47-54
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    • 2014
  • When an anchor penetrates and is installed under a seabed, a portion of the mooring line connected to the anchor is also embedded under the seabed. This embedded mooring line affects the capacity of the anchor in two ways. First, the frictional resistance that occurs between the mooring line and the seabed reduces the pulling force acting on the anchor. Second, the embedded part of the mooring line forms a reverse catenary shape due to the bearing resistance of the soil, so that an inclined pulling force is applied to the anchor. To evaluate the mooring line's effect on the capacity of an anchor in sand, centrifuge model tests were performed using two relative sand densities of 76% and 51% while changing the anchor depths. The test results showed that the load is reduced much more in deep and dense sand, and the inclination angle of the load is lower in shallow and loose sand.

Incorporating uplift in the analysis of shallowly embedded pipelines

  • Tian, Yinghui;Cassidy, Mark J.
    • Structural Engineering and Mechanics
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    • 제40권1호
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    • pp.29-48
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    • 2011
  • Under large storm loads sections of a long pipeline on the seabed can be uplifted. Numerically this loss of contact is extremely difficult to simulate, but accounting for uplift and any subsequent recontact behaviour is a critical component in pipeline on-bottom stability analysis. A simple method numerically accounting for this uplift and reattachment, while utilising efficient force-resultant models, is provided in this paper. While force-resultant models use a plasticity framework to directly relate the resultant forces on a segment of pipe to the corresponding displacement, their historical development has concentrated on precisely modelling increasing capacity with penetration. In this paper, the emphasis is placed on the description of loss of penetration during uplifting, modelled by 'strain-softening' of the force-resultant yield surface. The proposed method employs uplift and reattachment criteria to determine the pipe uplift and recontact. The pipe node is allowed to become free, and therefore, the resistance to the applied hydrodynamic loads to be redistributed along the pipeline. Without these criteria, a localised failure will be produced and the numerical program will terminate due to singular stiffness matrix. The proposed approach is verified with geotechnical centrifuge results. To further demonstrate the practicability of the proposed method, a computational example of a 1245 m long pipeline subjected to a large storm in conditions typical of offshore North-West Australia is discussed.

Nonlinear response of laterally loaded rigid piles in sand

  • Qin, Hongyu;Guo, Wei Dong
    • Geomechanics and Engineering
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    • 제7권6호
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    • pp.679-703
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    • 2014
  • This paper investigates nonlinear response of 51 laterally loaded rigid piles in sand. Measured response of each pile test was used to deduce input parameters of modulus of subgrade reaction and the gradient of the linear limiting force profile using elastic-plastic solutions. Normalised load - displacement and/or moment - rotation curves and in some cases bending moment and displacement distributions with depth are provided for all the pile tests, to show the effect of load eccentricity on the nonlinear pile response and pile capacity. The values of modulus of subgrade reaction and the gradient of the linear limiting force profile may be used in the design of laterally loaded rigid piles in sand.

Experimental and numerical study on the stability of slurry shield tunneling in circular-gravel layer with different cover-span ratios

  • Liu, Xinrong;Liu, Dongshuang;Xiong, Fei;Han, Yafeng;Liu, Ronghan;Meng, Qingjun;Zhong, Zuliang;Chen, Qiang;Weng, Chengxian;Liu, Wenwu
    • Geomechanics and Engineering
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    • 제28권3호
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    • pp.265-281
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    • 2022
  • A set of slurry shield test system capable of cutter cutting and slurry automatic circulation is used to investigate the deformation characteristics, the evolution characteristics of support resistance and the distribution and evolution process of earth pressure during excavating and collapsing of slurry shield tunneling in circular-gravel layer. The influence of cover-span ratio on surface subsidence, support resistance and failure mode of excavation face is also discussed. Three-dimensional numerical calculations are performed to verify the reliability of the test results. The results show that, with the decrease of the supporting force of the excavation face, the surface subsidence goes through four stages: insensitivity, slow growth, rapid growth and stability. The influence of shield excavation on the axial earth pressure of the front soil is greater than that of the vertical earth pressure. When the support resistance of the excavation face decreases to the critical value, the soil in front of the excavation face collapses. The shape of the collapse is similar to that of a bucket. The ultimate support resistance increase with the increase of the cover-span ratio, however, the angle between the bottom of the collapsed body and the direction of the tunnel excavation axis when the excavation face is damaged increase first and then becomes stable. The surface settlement value and the range of settlement trough decrease with the increase of cover-span ratio. The numerical results are basically consistent with the model test results.