• Title/Summary/Keyword: 마찰각

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Calculation of Wave Height due to Shoaling, Refraction and Bottom Friction on a Sloping Beach (일정 경사면에서 마찰을 고려한 파랑계산)

  • 서승남;오병철
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.2 no.3
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    • pp.128-133
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    • 1990
  • An equation is presented to calculate wave height due to shoaling, refraction and bottom friction. The equation in an integral form is evaluated by two different methods: A numerical method and an analytical method based on approximation. Both methods are used to calculate wave height and show very good agreement between their results. As shown in the figure of wave height variation vs. relative water depth, an increase of incident angle leads to a decrease in wave height. For the case of normal incident wave, the present equation can be reduced, under some assumptions, to the existing equation of Bretschneider and Reid (1954).

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Parmanent Grayvity Retaining Wall Displacment Due to Dynamic Loads (동적하중에 의한 중력식 옹벽의 영구변위)

  • 김성교
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.26 no.1
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    • pp.38-51
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    • 1984
  • Mononobe-Okabe에 의해서 옹벽에 대한 동적 토압계산법이 개발된 이래 본론두중 옹벽의 과동에 의한 변위에 대해서는 많은 연구가 이루어졌으나 Mononobe-Okabe식이 원래 옹벽 자체의 관성을 고려치 아니하였고 또 동적 하중의 작용점을 제시하지 않으므로서 전도모멘트를 계산할 수 없게 하므로서 옹벽의 전도에 의한 변위에 대해서는 연구가 되지 아니하였다. 본 연구의 목적은 해석적 방법과 모형실험을 통해서 지진 및 폭파 등의 동적 하중에 의한 옹벽의 전도에 의한 변위를 고찰하고자 하는 바 그 결과를 요약하면 다음과 같다. 1. 활동에 대한 항복가속도가 있는 것과 마찬가지로 전도에 대한 항복가속도가 있다. 이 항복가속도는 옹벽의 안전율이 증가함에 따라 증가한다. 2. 이론치와 실험치는 경향으로 보아 일치한다. 실험치가 이론치보다 작은 것은 모형실험에서 옹벽측면과 컨테이너 사이의 마찰에 기인한 것으로 보아지며 마찰을 줄임으로써 이론치에 더 접근시킬 수 있을 것이다. 3. 옹벽의 회전각도의 크기는 지반가속도가 클수록, 옹벽저면이 작을수록 그리고 흙의 내부마찰각이 작을수록 크게 증가한다. 4. 실용적인 규격의 옹벽의 변위는 활동에 의한 것보다 전도에 의한 것이 훨씬 크며 전체 변위의 대부분을 차지한다. 5. 옹벽 상단의 횡적 변위는 옹벽 설계를 결정짓는 중요한 요소가 될 수 있다.

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Relationship between Tangential Cohesion and Friction Angle Implied in the Generalized Hoek-Brown Failure Criterion (일반화된 Hoek-Brown 파괴조건식에 내포된 접선점착력과 접선마찰각의 상관성)

  • Lee, Youn-Kyou
    • Tunnel and Underground Space
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    • v.24 no.5
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    • pp.366-372
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    • 2014
  • The generalized Hoek-Brown (H-B) function provides a unique failure condition for a jointed rock mass, in which the strength parameters of rock mass are deduced from the intact values by use of the GSI value. Since it is actually the only failure criterion which accounts for the rock mass conditions in a systematic manner, the generalized H-B criterion finds many applications to the various rock engineering projects. Its nonlinear character, however, limits more active usage of this criterion. Accordingly, many attempts have been made to understand the generalized H-B condition in the framework of the M-C function. This study presents the closed-form expression relating the tangential cohesion to the tangential friction angle, which is derived by the non-dimensional stress transformation of the generalized H-B criterion. By use of the derived equation, it is investigated how the relationship between the tangential cohesion and friction angle of the generalized H-B criterion varies with the quality of rock masses. When only the variation of GSI value is considered, it is found that the tangential friction angle decreases with the increase of GSI, while the tangential cohesion increases with GSI value.

Study on Relationship Between Geographical Convergence and Bottom Friction at the Major Waterways in Han River Estuary using the Tidal Wave Propagation Characteristics (조석 전파 특성을 활용한 한강하구 주요 수로의 지형학적 수렴과 바닥 마찰 간의 관계에 대한 연구)

  • Yoon, Byung-Il;Woo, Seung-Buhm
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.23 no.5
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    • pp.383-392
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    • 2011
  • The basic research of the estuarine circulation at Gyeong-Gi bay has not been well studied up to now, although coastal development pressures have been continuously increased. To understand the oceanographic phenomena at the Han River estuary, it's essential to understand the propagation characteristic of tidal wave which is the strongest external forcing in this region. In this study, we investigate the tidal wave propagation characteristics along the 3 major channels using observation data and numerical model. It is found that 3 channels are all hyper-synchronous and the most important physical factor controlling the tidal wave propagation is topographical convergence of estuary shape and friction. The result of analytic solution at ideal channel considering the topographical convergence and friction show that the contribution of physical role of convergence and friction varies at 3 different channel. And the ratio of convergence and friction at Yeomha channel is four times larger than Seokmo channel. Because of this effect, the location of maximum amplitude at Yeomha channel is showed up downward than Seokmo channel. The ratio of decreasing amplitude and increasing phase per unit distance between stations is bigger than Seokmo channel. Although 3 major channel show a hyper-synchronous pattern, Yeomha shows more frictionally dominant channel and Seokmo channel is more dominantly affected by convergence effect.

Study of Ground Reinforced Effect using the Porous Geocell (다공성 지오셀을 이용한 지반 보강효과에 관한 연구)

  • Shin, Eun-Chul;Kim, Sung-Hwan;Kim, Young-Jin
    • Journal of the Korean Geosynthetics Society
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    • v.8 no.1
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    • pp.33-40
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    • 2009
  • The laboratory tests and field plate load test were carried out to evaluate the reinforcement effect of geocell for road construction. The geocell-reinforced subgrade shows the increment of cohesion and friction angle with comparison of non-reinforced subgrade. In addition, the field plate load test was performed on the geocell-reinforced subgrade to estimate the bearing capacity of soil. The direct shear test was conducted with utilizing a large-scale shear box to evaluate the internal soil friction angle with geocell reinforcement. The number of cells in the geocell system is varied to investigate the effect of soil reinforcement. The theoretical bearing capacity of subgrade soil with and without geocell reinforcement was estimated by using the soil internal friction angle. The field plate load tests were also conducted to estimate the bearing capacity with geocell reinforcement. It is found out that the bearing capacity of geocell-reinforced subgrade gives 2 times higher value than that of unreinforced subgrade soil. The settlement and the distribution of deformation were also estimated by using the finite element method. The magnitude of settlements on the geocell-reinforced subgrade and unreinforced subgrade are 6.8cm and 1.2cm, respectively.

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Characteristics for Horizontal Displacement of Temporary Earth Retaining Wall on Marine Sediments (해성퇴적층 지반의 가시설토류벽 수평변위 특성에 관한 연구)

  • Kim, Younghun;Kim, Chanki;Choi, Sungyeol;Chun, Byungsik
    • Journal of the Korean GEO-environmental Society
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    • v.11 no.11
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    • pp.37-45
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    • 2010
  • In this study, the value of numerical analysis was compared to the measured value of horizontal displacement during construction. And also, the value was reviewed by comparing with numbers calculated by SUNEX program and EXCAV program. When comparing to suggested values of the maximum horizontal displacement in clayey layer, the displacement caused by the IPS system is larger than one by the Strut girder type system. When comparing the result of SUNEX program to that of EXCAV program, the SUNEX program interprets larger value. It could be concluded the result of SUNEX program is closer to the suggested value, 0.5%H, in clayey layer. The result also shows that the internal friction angle(${\Phi}$) is the key factor of developing horizontal displacement rather than type of supporting systems or materials. That means small horizontal displacement occurs in sandy layer having large value of the internal friction angle, whereas vice versa in clayey layer having small value of the internal friction angle. Therefore, the result of EXCAV program is larger in sandy layer and vice versa in clayey layer. When comparing the measured result during construction to the value of 0.5%H, the measured result is 1.4 times greater than the value of 0.5%H. In contrast, the result of SUNEX program is only 78.1% of the value of 0.5%H and the one of EXCAV program is just 18.1% of that. This result shows the calculated value by SUNEX or EXCAV program is smaller than the observed value by measuring during construction. In result, more careful attention is needed to determine the behavior of the ground. To better analyze the behavior of the ground, more precise finite element method is required.

Friction Welding of Ni-Base ODS Alloy Prepared by Mechanical Alloying (기계적 합금법으로 제조된 Ni기 산화물 분산강화 합금의 마찰압접에 관한 연구)

  • 강지훈;박성계;김지순;권영순
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 1994.10b
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    • pp.15-15
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    • 1994
  • M MA ODS 합금의 보다 폭넓용 실용확훌 위해 크게 요구되고 있는 적정 접합기술 개발의 한 방안£로, 마찰압접(Friction Welding) 방법의 가능성옳 조사하기 위하여 마찰압력과 시간, 마 찰 후 접촉압력(Upset Pressure) 풍을 다양하게 변화시켜 접합체톨 제조한 후, 접합체 강도에 대한 인장시험과 접합계연의 결합 및 미세구조에 대한 현미경 관찰, EDS에 의한 원소분석, 접 합이옴부의 경도분포와 파단면 분석 풍율 행하였다. 실험에 사용된 모재는 기계적 합금법으로 제조된 Inca사의 Ni기 MA 754 합금이었으며, 직경 l 10 mm, 길이 50 mm로 가공한 후, 아세통£로 초음파 세척하여 접합에 사용하였다. 접합온 브 레이크식 마찰압접기틀 사용하여 행하였으며, 회전시험편의 회전수는 2400 rpm이었A며, 다른 한쪽의 고정시험편과의 마찰압력 및 마찰시간온 각각 50 - 500 MPa과 1-5초로, 또한 업셋압 력도 50 - 600 MPa로 변화시켰다. 이때 업셋압력은 모든 시편에 대해 일정하게 6초동안 가하 였다. 얻어진 접합체는 각 압접조건 당 2개 이상의 접합시험편에 대해 상온 인장강도톨 측정하 였으며, 파단이 일어난 위치를 확인한 후 파면에 대한 분석율 주사전자현미경(SEM)과 에너지 분산형 분광분석기mDS)릎 사용하여 행하였다. 컵합이옴부의 첩합성올 확인하기 위하여, 접합 체를 접합변에 수직으로 절단, 연마한 후 광학현미경과 SEM, EDS 퉁으로 관찰, 분석하여 접 합부의 형상과 결합형성 여부, 접합계면의 미세조직 퉁옳 조사하였다. 또한 마찰압접에 따론 모재와 접합계연부의 경도분포훌 접합이옴부로부터 모재쪽으로 일정 간격율 두어 마이크로 비 커스 경도기로 측정, 조사하였다. 이상의 설험 결과, 다옴과 같온 결론옳 얻었다. ( (1) 접합체 강도가 모채 강도의 95% 이상이 되는 양호한 렵합체흩 얻기 위한 마찰압력 조건 온, 2400 rpm의 회전속도와 6초의 업셋압력 유지시간에서 마찰압력과 업셋압력, 그리고 마찰시 간이 각각 400 MPa 이상과 500 MPa 이상,2초입율 확인하였다. ( (2) 컵합이옴부의 관찰 결과, 모든 마찰압접 조건에서 컵합이옴부는, 기폰 모재의 texture 조직 을 유지하고 있는 모재부 영역(영역 ill)과 첩합계면부에 인접하여 업셋압력이 주어질 때 단조 효과에 의해 계연 외부로 metal flow가 일어나면서 형성된 영역 II, 매우 미세한 결정립으로 구성된 중앙부의 영역 1 로 이투어져 있옴융 확인하였다. ( (3) 최적접합조건이 충족되지 않온 경우, 접합부의 영역 I 에서 관찰된 void와 균열, 불균일한 접합계면 통의 접합결함에 Al과 Y. Ti 퉁£로 구성된 산화물률이 용집되어 있옴을 확인하였 다-( (4) 접합체의 파단 양상온 크게 접합부 파단과 모재부 파단, 이률의 혼합형 파단i로 나눌수 있었다. 모재부 파단의 경우, 파단면이 매끄럽고 파변상의 결정립도 매우 미세하였으며, 산확물 의 용집도 찾아보기 어려웠 나, 접합부 파단의 경우에는 파변의 굴곡이 비교척 심하고 연성 입계파괴의 형태를 보였£며, 결정립도 모채부 파단의 경우에 비해 조대하였다. 조대하였다.

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Development of Failure Criterion of Hot Mix Asphalt Using Triaxial Shear Strength Test (삼축압축시험을 이용한 아스팔트 혼합물의 파괴기준 개발)

  • Kim, Seong Kyum;Lee, Kwan Ho
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.34 no.3
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    • pp.947-954
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    • 2014
  • In general, Fracture of the material is not occurring of the maximum normal stress or the maximum shear stress failure in the state. Maximum normal stress and maximum shear stress in the state of Critical coupling from being destroyed based on the Mohr-Coulomb theory. Couple of different mixtures, including permeable asphalt pavement, SMA and dense-graded asphalt mixture, were used for compression triaxial test at $45^{\circ}C$ and $60^{\circ}C$. Mohr-Coulomb theory to the analysis of compression triaxial test result of the internal friction angle $38.9^{\circ}{\sim}46.9^{\circ}$ measured somewhat irregularly, but in the case of cohesion, depending on whether the temperature and immersion of the specimen appeared differently. In addition, Indirect tensile test and compression triaxial test of the asphalt mixture to determine the correlation between compression triaxial test results assessed as cohesion and internal friction angle calculated using the theoretical Indirect tensile strength and measured indirectly tensile strength were analyzed. The Measured & Predicted IDT St values tended to be proportional.

Evaluation on Partially Drained Strength of Silty Soil With Low Plasticity Using CPTU Data (CPTU 데이터를 이용한 저소성 실트 지반의 부분배수 강도 평가)

  • Kim, Ju-Hyun
    • Journal of the Korean Geosynthetics Society
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    • v.16 no.2
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    • pp.55-66
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    • 2017
  • The standard piezocone penetration rate of 2 cm/s is proposed in specifications regardless of soil type. However, conditions of standard Piezo Cone Penetration (CPTU) Testings in silty soils with low plasticity vary from undrained to partially drained or fully drained penetration conditions. The partially drained shear strengths of Incheon, Hwaseong and Gunsan silty soils were estimated from the analysis results of the distributions of CPTU-based shear strengths. The CPTU-based shear strengths were compared between the undrained shear strength line and the fully drained shear strength line, which were determined from approximately ${\varphi}^{\prime}=3^{\circ}$ and ${\varphi}^{\prime}=15^{\circ}$, respectively. The internal friction angles obtained from the back analysis and UU-tests tended to increase with decreasing plasticity index, which range approximately from ${\varphi}^{\prime}=2^{\circ}$ to ${\varphi}^{\prime}=14^{\circ}$. The results matchs well with CPTU-based estimation results.

Active Eanh Pressure Against Caisson Backfilled with Crushed Rock and Sand (II) : Verification and Application (사석과 모래로 뒷채움된 케이슨에 작용하는 주동토압 (II) : 검증과 적용)

  • Paik Kyu-Ho
    • Journal of the Korean Geotechnical Society
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    • v.22 no.2
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    • pp.29-39
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    • 2006
  • In the companion paper (Paik 2006), a new formulation for calculating the nonlinearly distributed active earth pressure acting on a caisson backfilled with crushed rock and sand is proposed, and it takes into account arching effects as well as difference in internal friction angles and unit weights between sand and crushed rock. In this study, in order to partially check the accuracy of the proposed equation, the results of the proposed equation are compared with the equation proposed by Paik (2003a) for caissons with rough surface and homogeneous backfill, and are compared with results of Rankine's theory for caissons with smooth surface and homogeneous backfill. In addition, a parametric study is performed to investigate the effect of $phi_{r}$, $phi_{s}$, $\delta_{r}$, $\gamma_{r}$, $\gamma_{s}$ and $\beta$ on the magnitude of active earth pressure acting on the caisson, and construction methods for minimizing active earth pressure on the caisson are also provided based on the results of a parametric study.