On solving free surface problems in layered soil using the method of fundamental solutions

Jing-En Xiao, Cheng-Yu Ku ∗ , Chih-Yu Liu, Chia-Ming Fan, Weichung Yeih
Department of Harbor and River Engineering, National Taiwan Ocean University, Keelung, Keelung, Taiwan

Abstract

This paper presents the numerical solutions of free surface seepage flow in layered soil using the method of fundamental solutions (MFS). The numerical solutions are approximated by a set of fundamental solutions of the two-dimensional Laplace equation which are expressed in terms of sources located outside the domain of the problem. The unknown coefficients in the linear combination of the fundamental solutions which are accomplished by collocation imposing the boundary condition at a finite number of points can then be solved. To deal with the seepage problems of layered soil profiles, the domain decomposition method was adopted so that flux conservation and the continuity of pressure potential at the interface between two consecutive layers can be considered in the numerical model. The validity of the model is established for a number of test problems, including seepage problems in a rectangular dam, a trapezoidal dam, and an earth dam, by comparing numerical results with those from other methods. Application examples were also carried out. The results reveal that the proposed method based on the MFS has great numerical stability for solving seepage flow with nonlinear free surface in layered heterogeneous soil even with large contrasts in the hydraulic conductivity.

Keywords：Seepage, Free surface, Layered soil, The method of fundamental solutions, The domain decomposition method.

引用文獻

Jing-En Xiao, Cheng-Yu Ku*, Chih-Yu Liu, Chia-Ming Fan, Weichung Yeih (2017), “On Solving Free Surface Problems in Layered Soil Using the Method of Fundamental Solutions “, Engineering Analysis with Boundary Elements, Vol. 83, pp. 96-106. (IF 1.721, Q2 in ENGINEERING, MULTIDISCIPLINARY, JCR 2016)

Full paper link:

https://drive.google.com/file/d/0B31JQsw-BKEKMElfSV9jOVlRbnM/view?usp=sharing

恭喜本研究室通過科技部106年度多年期一般型研究計畫(整合型)

計畫名稱: 【 海岸開發利用與國土保護及環境風險評估－海岸地區地層下陷影響區域及風險評估 】

恭喜本研究室通過科技部106年度第2件研究計畫　(計畫主持人：顧承宇　教授)

恭喜本研究室劉芷妤與蕭靖恩同學通過博士班資格考試, 成為博士候選人

On the Accuracy of the Collocation Trefftz Method for Solving Two and Three Dimensional Heat Equations

Cheng-Yu Ku^a Jing-En Xiao^a Chih-Yu Liu^a Weichung Yeih^a

^a Department of Harbor and River Engineering, National Taiwan Ocean University, Keelung, Taiwan

ABSTRACT

In this article, the accuracy of the collocation Trefftz method (CTM) for solving two and three dimensional heat equations was investigated. The numerical solutions were approximated by superpositioning T-complete functions formulated using cylindrical harmonics. To avoid the ill-conditioned system of the CTM, the characteristic lengths and the multiple-scale Trefftz method were adopted. The results revealed that for two-dimensional problems, the CTM can provide highly accurate numerical solutions, with the accuracy increasing with the order of the terms. For three-dimensional problems, highly accurate numerical solutions can be obtained using a certain order of terms, where the order is determined by performing an accuracy assessment.

Keywords: Trefftz method; Ill-conditioned; Characteristic length; Cylindrical harmonics; Three dimensional

引用文獻

Cheng-Yu Ku*, Jing-En Xiao, Chih-Yu Liu, Weichung Yeih (2016), “On the Accuracy of the Collocation Trefftz Method for Solving Two and Three Dimensional Heat Equations”, Numerical Heat Transfer, Part B: Fundamentals: An International Journal of Computation and Methodology, Volume 69, Issue 4, pp. 334-350, 2016, http://dx.doi.org/10.1080/10407790.2015.1125215. (IF 1.330, SCIE, 30/58, Q2 in THERMODYNAMICS, JCR 2015)

Full paper link:

https://drive.google.com/open?id=0B6KIiA0ONNL1dnE0Ni0xNnh2NEE

臺灣地區離岸風機套筒式基樁承載特性分析之研究

摘要

本研究針對臺灣西部海岸離岸風機套筒式基樁承載特性進行分析。由於臺灣地理位置特殊位於環太平洋地震帶，地震活動十分頻繁，因此，離岸風機基礎在地震下之穩定性評估為重要之研究課題。此外，本研究針對海事工程有效應力孔隙水壓激發模式、海事工程土壤與流體耦合分析模式進行研究，以利風機基礎結構分析設計。臺灣西部海域離岸風場工址多屬海床沈積層，土層主要以砂土與黏土層為主，且一般較為鬆軟，因此，本研究提出一套新的離岸風機基礎設計流程，而離岸風機套筒式基樁之靜力與動力承載力分析是重之重點研究課題之一。由分析成果顯示，本研究之基礎設計分析可適切掌握土壤與基礎之互制行為，孔隙水壓激發模式能有效地模擬土壤液化現象，配合風機設計載重能檢核樁基礎承載力是否滿足設計需求，並利用動力分析得知基礎受震後之行為。
關鍵詞 : 動力分析、 孔隙水壓、海床土壤、離岸風場 、套筒式基礎

引用文獻

Cheng-Yu Ku*, Lien-Kwei Chien (2016), “Modeling of Load Bearing Characteristics of Jacket Foundation Pile for Offshore Wind Turbines in Taiwan”, Energies 2016, 9 (8), 625; doi:10.3390/en9080625. (IF 2.077, SCI, 43/88, Q2 in ENERGY & FUELS, JCR 2015)

全文下載

https://drive.google.com/open?id=0B6KIiA0ONNL1LTdaOXQwNEJWa3M

Article

Modeling of Load Bearing Characteristics of Jacket Foundation Piles for Offshore Wind Turbines in Taiwan

Cheng-Yu Ku * and Lien-Kwei Chien

Department of Harbor and River Engineering, National Taiwan Ocean University, Keelung 202, Taiwan;

Abstract: This paper presents a pioneering study on numerical modeling of load bearing characteristics of the jacket foundation pile for offshore wind turbines on the west coast of Taiwan. Because Taiwan is located in an earthquake prone area, there is significant interest in improving the prediction of the behavior of wind turbine jacket foundations subjected to seismic loading.  Investigation of the bearing capacity of the jacket foundation pile for the offshore wind farm using effective stress analysis, with consideration of pore pressure generation and soil/liquid coupled analysis, was conducted. A new procedure to evaluate the design of offshore wind turbine foundation piles in the sand and clay inter-layered soil was also proposed. Static and dynamic analyses of bearing capacity of the jacket foundation pile were conducted. Results obtained demonstrate that the design process for the jacket foundation pile proposed in this study can properly reflect the interaction behavior of the foundation and the soil. In addition, the pore pressure generation model can be used to simulate soil liquefaction. The proposed method is also very useful in the evaluation of the design capabilities of offshore wind turbine jacket foundations.

Keywords: dynamic analysis; pore pressure; seabed soils; offshore wind farm; jacket foundation

Cheng-Yu Ku*, Lien-Kwei Chien (2016), “Modeling of Load Bearing Characteristics of Jacket Foundation Pile for Offshore Wind Turbines in Taiwan”, Energies 2016, 9 (8), 625; doi:10.3390/en9080625. (IF 2.077, SCI, 43/88, Q2 in ENERGY & FUELS, JCR 2015)

Full paper download:

https://drive.google.com/open?id=0B6KIiA0ONNL1LTdaOXQwNEJWa3M

2016_J_energies-09-00625