اثرات شرایط مرزی در دقت و کارایی روش المان‌محدود برای تحلیل نابه‌جایی گسل درون نیم فضای ارتجاعی همگن

نوع مقاله : پژوهشی اصیل (کامل)

نویسندگان
حسین اسدی حیه
پویا زکیان
دانشکده فنی و مهندسی، دانشگاه اراک
چکیده
در این پژوهش، میدان جابه‌جایی سطح آزاد زمین براثر نابه‌جایی گسل در نیم‌فضای همگن ارتجاعی با روش المان‌محدود بررسی شده است. مرزها بر روی نتایج حاصل از روش المان‌محدود تاثیر شایانی دارند، به‌ویژه اگر دامنه مسئله دارای مرزهایی بی‌نهایت باشد. بنابراین باید تدابیر مناسبی برای افزایش کارایی و دقت روش اندیشیده شود. برای دستیابی به نتایج جامع در این زمینه، مدل‌سازی مرزها در این مقاله با دو رویکرد انجام شده است. رویکرد اول از المان‌‌های رایج برای مرزها استفاده می‌کند، اما رویکرد دوم از المان‌های ‌نامحدود بهره می‌جوید. برای راستی‌آزمایی نتایج، هر مسئله با چند شبکه گوناگون بررسی شده تا تاثیر شبکه نیز دیده شده و پاسخ‌های عددی با روابط تحلیلی اوکادا مقایسه می‌گردد. در کنار اثرات نوع مدل‌سازی مرزها تاثیر شبکه نیز دیده شده تا بتوان بر این اساس به رویکرد مناسب مدل‌سازی که با تعداد المان کمتری منجر به نتیجه مطلوبی می‌شود، دست پیدا کرد. در روند مدل‌سازی برای شبیه‌سازی نابه‌جایی گسل، از المان‌های تماسی استفاده شده است. نتایج بدست آمده حاکی از آن است که استفاده از المان نامحدود نه تنها برای مسائل نابه‌جایی لازم است بلکه موجب افزایش کارایی و دقت روش المان‌محدود می‌شود، به طوری که با شبکه‌های درشت‌تر می‌تواند به نتیجه مناسبی منجر شود.

کلیدواژه‌ها

موضوعات

عنوان مقاله English

The Effects of Boundary Conditions on Accuracy and Efficiency of Finite Element Analysis for Fault Dislocation within Homogeneous Elastic Half-Space

نویسندگان English

Hossein Asadi Hayeh
Pooya Zakian
Arak University
چکیده English

Surface deformation of the earth due to earthquake fault dislocation is very important for predicting ground motions. There are many studies on kinematic modeling of earthquake faults in both analytical and numerical methods. However, suitable investigations on improving usefulness and efficiency of those numerical methods are still necessary for relevant researchers. In this paper, displacement fields for free surface of the earth due to fault dislocation in homogeneous elastic half-space have been investigated by finite element method. Boundary conditions have significant effects on the results of finite element method, especially when the domain of the problem has infinite boundaries (half-space). Therefore, appropriate cares should be taken to increase the efficiency and accuracy of this method. In order to achieve a comprehensive study on this topic, boundaries have been modeled by two approaches here. The first approach uses common elements for infinite boundaries, while the second one uses infinite elements for those boundaries. To verify the results, each problem has been examined by several meshes and numerical solutions have been compared to Okada’s analytical solutions. In addition to the effects of the boundary modeling, the discretization effects have been investigated in order to find a suitable approach to reduce computational efforts and to increase the accuracy and efficiency of finite element method. In the modeling process, contact elements have been employed to impose fault dislocation. Three numerical examples have been provided for these finite element analyses. Each example includes four analyses without infinite elements and three analyses with infinite elements which are also compared together. The results show that not only infinite elements are necessary for quasi-static fault dislocation problems, but also they improve the performance of finite element method, so that with finer meshes and smaller dimensions of a domain, analytical solutions can be captured by numerical solutions with suitable accuracy.

کلیدواژه‌ها English

Fault dislocation
Numerical simulation
Infinite element
Elastic half-space
finite element method
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مهندسی عمران مدرس
دوره 20، شماره 6
آذر و دی 1399
صفحه 75-87