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The Study of Dynamic Behavior of the Seabed Soil by Cyclic Triaxial and Torsional Test system to Simulate the Typhoon-Induced Wave Loading
|Authors: ||Wei-Ting Chen|
|Contributors: ||NTOU:Department of Harbor and River Engineering|
|Issue Date: ||2011-11-23T03:18:38Z
|Abstract: ||波浪在海床土壤傳遞的過程中，海床內部土壤受波浪外力作用下，會對內部產生動態壓力，當壓力傳遞到海床內部，會使海床土壤同時受到垂直應力、水平應力、孔隙水壓及扭剪應力的相互影響，使海床土壤產生不穩定,而導致破壞。 本研究為了更深入的探討在波浪作用下，動態壓力傳遞至海床土壤的過程中，海床土壤受力的真實情況，將原先發展的三向動力三軸系統結合扭剪應力功能加以整合，可由電腦控制軸向、圍壓與反水壓，及扭剪應力之各種應力條件，使系統可完全模擬波浪傳遞至海床內部時所產生的四種應力情況，並將系統由半自動控制整合成全自動控制，且改可直接輸入所需之扭力即可施做試驗，模擬海床受水平剪應力作用下之結果能更接近海床實際受力狀態。 本研究主要探討利用相同的波浪條件，在不同深度下操作三軸動力扭剪系統，包含三軸軸向、三軸扭剪及軸向結合扭剪應力之三軸系統，三種不同試驗，討論其三種系統試驗下，其孔隙水壓的變化與差別。 颱風碎波點之軸向、扭剪及軸向結合扭剪試驗結果，以Seed (1976)及張志新(2004)孔隙水壓激發模試探討，發現在三軸軸向試驗時兩者皆可有效的預測孔隙水壓，而三軸扭剪及三軸軸向結合扭剪試驗，因前人皆未考慮扭剪應力的施加的影響，故孔隙水壓激發初期兩預測模式皆有明顯落差。孔隙水壓激發值若以三軸扭剪試驗結果為基準，三軸軸向試驗結果，於本研究孔隙水壓激發值最大差異值可達10%，軸向結合扭剪試驗結果，孔隙水壓激發值最大差異值達26%。本研究所建置動力三軸結合扭力試驗系統與初步之試驗結果，期能對於後續海床土壤受波浪動態作用之相關研究，能有所助益。|
During the process of wave transmitting into the seabed, the internal seabed soil was induced the dynamic pressure under wave loading. While the wave pressure was transmitted into the internal seabed, the seabed soil was subjected to the interaction of vertical stress, horizontal stress, pore water pressure and torsional stress at the same time. It was led to the seabed failure due to the seabed soil be in the unstable condition. This research in order to discuss the natural condition of the soil under the wave of the process that dynamic pressure transmitted to the soil of seabed. It integrates the earlier developed triaxial cyclic testing system with torsion shear stress function analysis. It can set any kinds of the control model for various stress condition including axial,confining pressure,back water pressure and torsional shear stress by the computer. This system can simulate completely the situations of four stresses when the wave acting on the seabed. We can change the system from semi-automatic control mode to full-automatic control mode and direct input the data of torsional moment to do the tests. The results of simulating the force under the horizontal shear stress more approach to the real condition of seabed under forces. In this study, mainly discuss how to use cyclic axial and torsional system to operate testing simulations with same initial wave conditions in different sea depth. It includes axial tests,torsional tests,and axial combined with torsional shear stress tests . Under these three kinds of test we can analyse the variation and difference of pore pressures. The analysis for test results of the typhoon breaking point simulated with axial, torsional,and axial combined with torsional shear stress systems reference with the paper researches discussing pore water pressure build-up modes by Seed(1976) and Chang(2004).We indicated that the axial simulation can effectively predict the pore pressure for both modes. The initial predictions of pore water pressure build-up with torsional,and axial combined with torsion shear stress systems have significant differences. It made by the operating testing simulations without considering the factor of torsional shear stress. If the active threshold of pore water pressure build-up based on the cyclic torsional test results, the triaxial test results with this study could get the maximum underestimated value approach to 10% .The results of cyclic triaxial and torsional tests could get the maximum underestimated value approach to 26% . This study proposes the simulation results and establishes the cyclic triaxial testing system(TCTS) combined cyclic torsional system to simulate the actual seabed condition. We hope it could contribute to the study of the seabed soil under the wave loading.
|Appears in Collections:||[河海工程學系] 博碩士論文|
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