• Title/Summary/Keyword: 점성력

Search Result 246, Processing Time 0.03 seconds

Fundamental Study on the Reinforcing Effect of Reinforced Clayey Soil with Nonwoven-geotextile (부직포 보강 점성토의 보강효과에 관한 기초적 연구)

  • 김유성;이재열
    • Geotechnical Engineering
    • /
    • v.14 no.4
    • /
    • pp.61-76
    • /
    • 1998
  • Various kinds of reinforced soil methods have been developed by many researchers or companies for their economic merits mainly. These methods have generally used sandy soils which have high permeability as embanking or backfill material. That is because, if poor embanking materials, especially like a clayey soil which has very low permeability, are used in a reinforced soil embanking, and if excessive pore water pressure is produced by external factors, the friction resistance between reinforcing members and Boils decrease, as a result possible damage or collapse of the body of a reinforced embankment. In fact, clayey Boils can also be used as a embanking materials with reinforcement which has high permeable capacity, and are expected to be able to dissipate the excess pore water pressure effectively. In this study reinforcing effects have been examined through a serries of direct shear tests in which clayey soils are reinforced with nonwoven geotextiles of which permeability is very high and tensile strength is relatively weaker than geogrids which are usually used in reinforced soil wall. Even though such nonwoven geotextile are used as reinforcement of high saturated clayey soils. the test results show the possibility that nonwoven geoteztiles could be used as a reinforcement for reinforced soil walls effectively.

  • PDF

Optimum design of propulsion shafting system considering characteristics of a viscous damper applied with high-viscosity silicon oil (고점도 실리콘오일 적용 점성댐퍼 동특성을 고려한 추진축계 최적 설계)

  • Kim, Yang-Gon;Cho, Kwon-Hae;Kim, Ue-Kan
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.41 no.3
    • /
    • pp.202-208
    • /
    • 2017
  • The recently developed marine engines for propulsion of ships have higher torsional exciting force than previous engines to improve the propulsion efficiency and to reduce specific fuel oil consumption. As a result, a viscous damper or viscous-spring damper is installed in front of marine engine to control the torsional vibration. In the case of viscous damper, it is supposed that there is no elastic connection in the silicon oil, which is filled between the damper housing and inertia ring. However, In reality, the silicon oil with high viscosity possesses torsional stiffness and has non-linear dynamic characteristics according to the operating temperature and frequency of the viscous damper. In this study, the damping characteristics of a viscous damper used to control the torsional vibration of the shafting system have been reviewed and the characteristics of torsional vibration of the shafting system equipped with a corresponding viscous damper have been examined. In addition, it is examined how to interpret the theoretically optimal dynamic characteristics of a viscous damper for this purpose, and the optimum design for the propulsion shafting system has been suggested considering the operating temperature and aging. when the torsional vibration of the shafting system is controlled by a viscous damper filled with highly viscous silicon oil.

Characteristics of Bearing Capacity and Stress Concentration of Clay Ground Improved with Sand Compaction Piles (SCP 보강 점성토 지반의 지지력 및 응력분담특성)

  • Yoo Nam-Jae;Park Byung-Soo;Jeong Gil-Soo;Koh Kyung-Hwan;Kim Ji-Sung
    • Journal of the Korean Geotechnical Society
    • /
    • v.21 no.1
    • /
    • pp.81-91
    • /
    • 2005
  • This paper is the results of experimental and numerical works on the investigating design factors influencing the bearing capacity, the ratio of stress concentration, and the failure mechanism of the clay ground improved with sand compaction piles (SCP). In order to find the behavior of the clay ground improved with SCP, extensive centrifuge model experiments were carried out for each of the SCP replacement ratio of 20, 40, and $70\%$, the non-plastic fine contents in sand of 5, 10, and $15\%$, and the ratio of the improved width to the loaded area (W/B) of 1, 2, and 3. The commertially available software of FEM, CRISP, was used to analyze test results by performing numerical estimations. In these numerical analyses the sand compaction piles and the clay ground were simulated as a linear elastic and plastic constitutive model and the modified Cam-clay model, based on Critical State Soil Mechanics, respectively.

A Study on Estimation of the Collapse Pattern of Road Sink Using Distinct Element Method (개별요소법을 이용한 도로함몰 붕괴양상 추정에 관한 연구)

  • Ham, Myoung Soo;Park, Seon Woo;Lee, Hyun Dong
    • Journal of Korean Society of Disaster and Security
    • /
    • v.12 no.2
    • /
    • pp.57-63
    • /
    • 2019
  • The road sinks in the sewer line or subway section are affected by the ground characteristics. Therefore, it is necessary to accurately identify the relationship between the soil properties and the ground motion in the area where cavities occurred in order to establish a countermeasure against the road sink. In this paper, simulation was performed by using EDEM program, which is one of the Discrete Element Method programs, for sandy soil and clayey soil, which are most common in alluvial deposits, with different locations and sizes of cavities in the underground. As a result, it was found that the sink size occurred more in the sandy soil than in the cohesive soil. Deeper and larger cavity is more likely to occur the road sink In the sand soil model while road sink in the clay model is easy to occur when the cavity is more shallower.

Seismic Design of Anchored Sheet Pile Walls in c-0 Soils (점성토 지반에 설치되는 앵커로 지지된 널말뚝의 내진설계)

  • 김홍택
    • Geotechnical Engineering
    • /
    • v.8 no.1
    • /
    • pp.41-58
    • /
    • 1992
  • In the present study, an analytical solution method is proposed for the seismic design of anchored sheet pile walls used in port. The proposed analytical method deals with the anchored sheet pile walls with free earth support in sands and c- U soils, including the effects of hydrodynamic pressures and a condition of steady seepage between the two water levels. Also, the effects of various parameters(differential in water levels, anchor position, wall friction angle, dredge line slope, cohesion, adhesion etc.) on embedment depth, anchor force, and maximum bending moment are analyzed using the proposed method. In addition, comparisons between different definitions of safety factor are made, and necessary considerations required in the design of anchored sheet pile walls are examined.

  • PDF

Dynamic Analysis of the Small Reciprocating Compressors Considering Viscous Frictional Force of a Piston (피스톤의 점성 마찰력을 고려한 소형 왕복동 압축기의 동적 해석)

  • 김태종
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.12 no.11
    • /
    • pp.904-913
    • /
    • 2002
  • In this study, a dynamic analysis of the reciprocating compression mechanism considering viscous friction force of a piston used in small refrigeration compressors is performed. The length of cylinder in this class of compressors is shortening to diminish the frictional losses of the piston-cylinder system. So, the contacting length between piston and cylinder liner is in variable with the rotating crank angle around the BDC of the reciprocating piston. In the problem formulation of the compression mechanism dynamics, the change in bearing length of the piston and all corresponding viscous forces and moments are considered in order to determine the trajectories of piston and crankshaft. The piston orbits for viscous friction model and Coulomb friction model were used to compare the effect of the friction forces of piston on the dynamic trajectories of piston. To investigate the effect of friction force acting on the piston for the dynamic characteristics of crankshaft, comparison of the crankshaft loci is given in both viscous model and Coulomb model. Results show that the viscous friction force of piston must be considered in calculating for the accurate dynamic characteristics of the reciprocating compression mechanism.

Simulation for the Propulsion of Micro-Hydro-Machine with Unstructured Grid (비정규 격자를 이용한 극소 로봇의 추진 해석)

  • Moon-Chan Kim;Dong-Dai Ha
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.39 no.3
    • /
    • pp.1-7
    • /
    • 2002
  • Flow mechanism of contractive and dilative motion is numerically investigated to obtain a propulsive force in highly viscous fluid, which is the simulation of the propulsion in micro-organisms. The computing code for the analysis of complicated motions is developed with cell-centered unstructured grid scheme. The developed code is validated by the well-known problems of cavity flow and oscillating wall. The validated code is applied to the contractive and dilative motion in narrow tube. The computed results are compared with nodal points scheme. By the present results, it is found that propulsive force can be obtained by the contractive and dilative motion through simulation with the developed code.

Study on the Viscous Roll Damping around Circular Cylinder Using Forced Oscillations (강제동요를 이용한 원형실린더 점성 롤댐핑 연구)

  • Yang, Seung-Ho
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.18 no.2
    • /
    • pp.71-76
    • /
    • 2017
  • The roll damping problem in the design of ships and offshore structures remains a challenge to many researchers due to the fluid viscosity and nonlinearity of the phenomenon itself. In this paper, the study on viscous roll damping of a circular cylinder was carried out using forced oscillations. The roll moment generated by forced oscillation using a torque sensor was measured for each forced oscillation period and compared with the empirical formula. Although the magnitude of the measured torque from the shear force was relatively small, the results were qualitatively similar to those obtained from the empirical formula, and showed good agreement with the quantitative results in some oscillation periods. In addition, the flow around the circular cylinder wall was observed closely through the PIV measurements. Owing to the fluid viscosity, a boundary layer was formed near the wall of the circular cylinder, and a minute wave was generated by periodical forced oscillations at the free surface through the PIV measurement. In this study, the suitability of the empirical formula for the roll moment caused by viscous roll damping was verified by model tests. The wave making phenomenon due to the fluid viscosity around the wall of a circular cylinder was testified by PIV measurements.

Load Transfer of Ground Anchors in Clay (점토지반에 설치된 앵커의 하중전이에 관한 연구)

  • Kim, Nak-Kyung
    • Journal of the Korean Geotechnical Society
    • /
    • v.16 no.3
    • /
    • pp.145-155
    • /
    • 2000
  • 지반과 구조물을 일체화시키는데 사용하는 앵커는 앵커체와 지반의 마찰력에 의해서 구조물을 지지하는 역할을 하며 앵커의 하중과 변형의 관계를 규명하기 위해서는 앵커의 마찰력 분포의 변화(하중전이)가 중요한 요소가 된다. 하중 재하시 앵커체에 발생하는 하중전이 분포는 앵커의 인발 지지력과 밀접한 관계가 있고 정착장의길이, 지반 조건 등에 따라 분포 양상이 변하기 때문에 하중 정이를 이해하기 위해서는 강선과 그라우트의 하중분포 그리로 앵커 그라우트체와 지반과의 마착력 분포를 알아야 한다. 본 연구는 미국 Texax A&M University의 점성토지반에 계측기가 장착된 10개의 그라운드 앵커를 설치하여 인발시험을 수행하였다. 앵커의 자유장 강선에 작용하는 응력, 그라우트체에 작용하는 응력, 그리고 정착장 강선의 응력을 계측하여 강선과 그라우트의 정착응력 및 그라우트와 지반에서의 마찰력 분포를 구함으로써 강선-그라우트-지반의 복합적인 거동에 따른 각 하중 단계마다의 하중전이를 얻어냈다. 또한 현장시험 결과의 역해석을 통하여 강선과 그라우트 사이의 하중과 변위의 관계와 그라우트와 지반의 하중-변위 관계를 분석하여 그라운드 앵커의 인발 특성을 예측 할 수 있는 수치해석 기법을 모델링하여 제시하였다.

  • PDF

Experimental study on the damping characteristics of a cylindrical structure containing oil and bearing balls (윤활유와 베어링 볼을 내장한 원통형 구조물의 감쇠특성에 관한 실험적 연구)

  • 류봉조;송선호
    • Journal of KSNVE
    • /
    • v.6 no.1
    • /
    • pp.107-114
    • /
    • 1996
  • The damping characteristics of a cylindrical structure containing oil and bearing balls is investigated for external bending forces. The experimental data obtained through the use of bearing balls with viscous oil in a column is given and analyzed. The viscous action of the oil and inertia effects of the balls on the inside of column create a drag force. The drag force dampens the vibration of the column. This study aims to search for an optimum combination of oil and balls which would produce maximum damping. Machining oils of various viscosities along with ball bearings of various sizes place inside cantilevered aluminium tubes of various diameters to create a rig on which the damping properties of the oil and balls can be studied. The contileved tubes are studied in both horizontal and vertical positions in order to gauge the effect of gravity on the system. The actions of the ball in the column and damping characteristics are investigated according to the dimensionless terms. The Buckingham theorem is used to reduce the variables and to predict the damping of an oil ball column. Though the damping ratio remains fairly constant in the horizontal position of column, the damping ratio begins to increase as the ratio of the number of balls and column length rise above 0.28 in the vertical position of oil ball column. The ratio of the ball diameter to column diameter influences the damping ratio with an optimum diameter ratio. Slenderness ratio and gravity effects on the damping ratio ane investigated.

  • PDF