해저관로 주변의 국부세굴에 관한 연구 = Local scour around submarine pipeline

다국어 초록 (Multilingual Abstract)

Submarine pipelines are used in coastal structures. The pipelines are installed in marine environments for transportation of gas and crude oil from offshore platforms, and for the disposal of industrial and municipal waste water into the sea.
In order to ensure these pipelines are stable and functional during their project life, attention must be paid to their design and coastal processes. In the design phase, the possibility of local scouring under submarine pipelines must be taken into consideration.
When a structure such as a pipeline is placed in a marine environment, the very presence of the structure will change the flow and wave field in its immediate neighborhood, resulting in one or more of the following phenomena: The contraction of flow; the formation of a horseshoe vortex in front of the structure; the formation of lee-wave vortices(with or without vortex shedding) behind the structure; the generation of turbulence; the occurrence of reflection and diffraction of waves; and the occurrence of wave breaking.
These changes usually cause an increase in the local sediment transport capacity, and thus lead to scour. Scour is a threat to the stability of the structure.
In this study, the characteristics of local scour on submarine pipelines were investigated by hydraulic model tests. To do this, open channel was used in current condition and wave generator was used in waves condition.
In the case of steady current, the experiments were done in a horizontal bed. The pipe diameter(D) and flow velocity(V) were varied. In the case of wave, the experiments were done in a horizontal and a slope bed. The wave height(H), the wave period(T) and the embedment depth were varied.
Scour depth and development of scour near the pipeline are observed due to variation of flow velocity, pipe diameter, wave height and wave period. The experiments showed that the maximum equilibrium local scour depth increases with the flow velocity(V), the pipe diameter, the wave height and the wave period.
The correlations of scour depth and parameters such as a Reynolds number(Re), Shields number(), Froude number(Fr), Keulegan -Carpenter number(KC), Ursell number() and modified Ursell number() were analyzed.
In the condition of steady current, Froude number is the main parameter to cause the local scour around the submarine pipelines. In the case of wave condition, KC number and modified Ursell number are main parameters to cause the local scour around the submarine pipelines.

목차 (Table of Contents)

• Abstract ⅳ
• List of tables ⅶ
• List of figures ⅷ
• Notations xiii
• Ⅰ. 서 론 1
• 1.1 연구의 필요성 및 목적 1
• 1.2 연구동향 4
• 1.3 연구의 범위 및 방법 9
• Ⅱ. 해저세굴과 매개변수 11
• 2.1 해안에서의 세굴 11
• 2.1.1 정상흐름에서의 국부세굴 11
• 2.1.2 파랑상태에서의 국부세굴 13
• 2.2 정지상 세굴과 이동상 세굴 15
• 2.3 터널침식 16
• 2.4 관로 주변 환경에 따른 2차원 세굴 18
• 2.4.1 배후류 침식 19
• 2.4.2 세굴심 20
• 2.5 세굴 관련 매개변수 26
• 2.5.1 Reynolds 수 28
• 2.5.2 Shields 수 29
• 2.5.3 Froude 수 30
• 2.5.4 Ursell 수와 수정 Ursell 수 31
• 2.5.5 Keulegan-Carpenter 수 32
• Ⅲ. 정상흐름에서 관로 주변의 국부세굴 34
• 3.1 실험장치 및 방법 34
• 3.2 관로 주변의 국부세굴 38
• 3.3 세굴 영향인자에 따른 세굴심의 변화 41
• 3.4 매개변수에 따른 상대세굴심의 변화 50
• Ⅳ. 파랑에서 관로 주변의 국부세굴 53
• 4.1 수평하상에 설치된 관로 주변의 국부세굴 53
• 4.1.1 실험장치 및 방법 53
• 4.1.2 수평하상에 설치된 관로 주변의 국부세굴 58
• 4.1.3 세굴 영향인자에 따른 세굴심의 변화 64
• 4.1.4 매개변수에 따른 상대세굴심의 변화 70
• 4.2 경사하상에 설치된 관로 주변의 국부세굴 75
• 4.2.1 실험장치 및 방법 75
• 4.2.2 경사하상에 설치된 관로 주변의 국부세굴 77
• 4.2.3 세굴 영향인자에 따른 세굴심의 변화 82
• 4.2.4 매개변수에 따른 상대세굴심의 변화 87
• 4.3 수평하상에 매설된 관로 주변의 국부세굴 93
• 4.3.1 실험장치 및 방법 93
• 4.3.2 수평하상에 매설된 관로 주변의 국부세굴 96
• 4.3.3 세굴 영향인자에 따른 세굴심의 변화 102
• 4.3.4 매개변수에 따른 상대세굴심의 변화 111
• 4.4 불완전 세굴 116
• Ⅴ. 결 론 121
• 참고문헌 123
• 감사의 글 129