碩士 / 國立臺灣海洋大學 / 河海工程學系 / 101 / In recent years, the climate change often caused the offshore extreme meteorology.It could be induced the seabed soil liquefaction and unstable phenomenon at nearshore area. In this study, the program of GeoStudio QUAKE/W was adopted to simulate the stress analysis of seabed soil under the wave loading.The model of seabed soil liquefaction and stablility analysis was established under wave extreme typhoon wave loading of nearshore area to evaluate the seabed soils subjected to the different extreme typhoon waves (as 50 years, 100 years, 200 years return period).The stress distribution, pore water pressure distribution, effective stress distribution and liquefaction analysis of seabed soil were simulated by use of the program. And the possible caused the range of seabed soil liquefaction was dicussed to ensure Taiwan's Yunlin nearshore seabed soil stability and marine cable safty. On the other hand,by use of Chen and Yang (1996) of seabed liquefaction potential assessment method compared with this study method.Considering the different seabed slopes, relative densities, and depths, the stress distribution and liquefaction range of seabed soil were evaluated. It can be provide the reference of prevention disaster or reduce risk of damage.
Through the GeoStudio program to simulate under extreme typhoon wave loading (as 50 years, 100 years, 200 years return period), the seabed soil stress distribution, pore pressure distribution and liquefaction analysis were evaluated.And the final simulated results, the range of seabed soil liquefaction were established. When the return period is 50 years,the deepest of seabed soil liquefaction under typhoon wave loading about reaches 12 meters; When the return period is 100 years, the deepest of seabed soil liquefaction under typhoon wave loading about reaches 15 meters.And when the return period is 200 years, the deepest of seabed soil liquefaction about reaches 16 meters. The nearshore distribution depth of the seabed soil liquefaction ranges from 30 meters to 0.88 meters.
Other hand,because the method of Chen &; Yang (1996) is mainly considered a wave condition parameters(as soil shear stress ratio, relative depth, wave length), and the main considering of the program analyzes of this study is the soil material parameters(as shear modulus, Young's modulus, the relative density).Form the analysis results indicated that the distribution range of seabed soil liquefacitob by the method of Chen &; Yang (1996) with this study mode programs have same tendency. It is useful for the design of nearshore submarine buried cables,prevent damage and nearshore structure stability. When the sea bed slope is 30%, and the reltive ranges depth form 30 meters to 0.88 meters have relatively wide. Therefore, the range of seabed soil liquefaction under the slope of 30% is widely than the slope of 40%. The relative density of 35% of seabed soil is easy induced liquefaction than the relative density of 55%.Thus, the liquefied range under relative density of 35% is wider than the relative density of 55%.
From the engineer case study analysis shown that the depth of 7 meters could be occurred seabed soil liquefaction under the typhoon waves loading (as the return period of 50 years, 100 years, and 200 years). The main possible reason is the seabed soil layer is belong to the loose and soft sand and easy to cause liquefaction. Because the field seabed soil below 7 meters has a moderate dense sand layer, it more difficult to cause soil liquefaction. Therefore, there will be caused liquefaction range parallel with sebed surface. From the pipeline displacement analysis, the relative displacement of seabed pipeline will cause period behavior under period wave loading.When the typhoon wave loading, the maximum vertical displacement of pipeline could be up to about 0.24m.While the deeper water depth pipeline does not induce displacement, and will be more stable.So, when considering the design the embedded pipelines depth, the depth can be considered as the displacement of the pipeline design. This study established the model of seabed soil liquefaction and stability analysis can be applied to western Taiwan’s sandy nearshore area and to provide the reference of nearshore seabed soil liquefaction and pipeline stability analysis.
| Identifer | oai:union.ndltd.org:TW/101NTOU5192046 |
| Date | January 2013 |
| Creators | Shih-Chi Tzou, 鄒世琦 |
| Contributors | Lien-Kwei Chien, 簡連貴 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 144 |
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