Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/12938
標題: 波浪與海床土壤交互作用之解析
Theoretical Approaches on Water Waves Interactions with Porous Seabed
作者: 李宗霖
Lee, Tsong-Lin
關鍵字: Porous Seabed
多孔隙介質海床
wave-seabed interaction
wave dispersion relationship
the inertia forces of soil
Coulomb-damping friction
波浪與海床的交互作用
波浪散播方程式
土壤慣性力
庫侖-阻尼摩擦效應
出版社: 土木工程學系
摘要: 本文旨在解析並探討波浪作用於一平坦、有限厚度且具有均勻滲透性孔隙介質的海床時,土壤的動力反應與波浪流場變化的交互作用問題。 往昔大多數文獻對於波浪作用於海床土壤的動力反應問題,多假設海床表面為剛性不透水,考慮海床表面上之波動壓力係直接貫入土壤內部,無法進一步研究波浪流場受底床土壤反應所導致變化的交互作用問題,因此並非嚴謹地探究海床土壤的動力反應。基此,本研究的第一個重點,係以Biot多孔彈性理論為基礎,考慮海床表面土壤滲透性之速度連續條件,將波浪之速度勢中的波浪週波數以未知數型式表示,進行解析。文中為探討土壤慣性力對海床反應之影響,並於原始孔隙介質控制方程中加入慣性項。藉由解析結果之波浪散播方程式(dispersion relationship),可清楚地發現海床土壤的特性對波浪流場反應的影響,如波浪衰減、波長變化及底床表面壓力等特性,明顯地受土壤反應之影響而發生變化。文中對有限厚度土壤內孔隙水壓力、有效應力、土壤位移及滲流力等特性,亦有詳細的探討。另外,土壤慣性力對土壤反應的影響,隨著土壤飽和度之降低而逐漸增大。 本研究的第二個重點則進一步考慮土壤內庫侖-阻尼(Coulomb-damping)摩擦效應的影響,解析波浪與海底床之交互作用。文中除將透水彈性體中固體結構與孔隙流體分開推導其個別運動方程式外,並考慮水波作用於土壤內部時,產生三種彈性波,即兩種壓力波及一種剪力波。由於剪力波對低滲透率的土壤有重要的影響,因此在波浪與海床交互作用的問題時,庫侖阻尼摩擦效應的作用顯得重要。經理論計算結果發現,具有庫侖阻尼摩擦效應的細砂或黏土海床對土壤動力反應有明顯的影響,且波浪流場的變化,仍以細砂或黏土海床之影響最為顯著。
In the past few decades, considerable efforts have been devoted to the phenomenon of wave-seabed interaction. However, most previous works have been only concerned with the seabed response under the wave pressure, which was obtained from the assumption of a rigid seabed. In such approaches, the whole wave-seabed interaction cannot be fully investigated. The first aim of this study is to investigate the dynamic response of seabed to ocean surface waves. The inertia forces are considered in the whole problem. Based on Biot's poro-elastic theory, the problem of wave-seabed interaction is first treated analytically for a homogeneous bed of finite thickness. With the newly general solution of seabed response, a new wave dispersion relationship is obtained, in which the soil characteristics are included. Based on the numerical results presented in this study, it is found that the effects of soil parameters significantly affect the wave characteristics (such as the damping of water wave, wave length and wave pressure). Furthermore, the effects of inertia forces on the wave-induced seabed response cannot always be ignored under certain combination of wave and soil conditions. The second aim of this study is to further consider the effects of Coulomb-damping friction within the soil skeleton, which most previous investigations have neglected. In general, three types of elastic waves are induced in a seabed by the water wave: a shear waves and a compressional wave in the soil skeleton, and a compressional wave in the pore fluid. Since the shear wave plays an important role due to the low rigidity and permeability of the fine sand and clay, the effects of Coulomb-damping friction on the phenomenon of the wave-seabed interaction are indeed to be examined. The numerical results indicate that the Coulomb-damping effect significantly affects the wave-induced soil response in a soft seabed (such as fine sand and clay). Also, the wave characteristics have been significantly affected by the wave-induced seabed response, especially in the fine sand and clay.
URI: http://hdl.handle.net/11455/12938
Appears in Collections:土木工程學系所

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