بهسازی لرزه‌ای سد بتنی وزنی تقویت‌شده با حائل نگهدارنده آسفالتی

نوع مقاله : علمی - پژوهشی

نویسندگان

مهندسی عمران، دانشکده مهندسی، دانشگاه زنجان، زنجان، ایران

چکیده

در این پژوهش، تحلیل لرزه‌ای غیرخطی سد بتنی وزنی تقویت‌شده به وسیله‌ی حائل نگهدارنده آسفالتی ارائه شده است. حائل نگهدارنده آسفالتی ایستا در پایین‌دست سد بتنی وزنی، اغلب به عنوان یک روش تقویتی برای بهبود پایداری سدهای موجود در مقابل بارگذاری هیدرواستاتیکی و لرزه‌ای مورد توجه قرار می‌گیرد. جهت نشان دادن تأثیر حائل نگهدارنده بر بهبود پاسخ لرزه‌ای سد وزنی بتنی و کاهش ترک‌های ایجاد شده در نزدیکی بدنه‌ی بالادست و به دنبال آن افزایش پایداری سد، پاسخ سد Koyna در کشور هند تحت آنالیز و تحلیل قرارگرفته شده است. تحلیل‌های دینامیکی خطی و غیرخطی با در نظر گرفتن رفتار غیرخطی بتن با دیدگاه ترک پخشی ثابت (FCM) به کمک نرم‌افزار ANSYS جهت بررسی رفتار لرزه‌ای سازه انجام شده‌اند. در تحلیل‌ها، اندرکنش سد- مخزن در نظر گرفته شده است. تحلیل‌ها با اعمال مؤلفه‌های افقی و قائم شتاب‌نگاشت زمین‌لرزه Koyna به مدل لحاظ شده‌اند. مدل‌سازی‌ها تحت حالاتی که در آن، سد بدون حائل و دارای حائل آسفالتی متصل به سطح بدنه‌ی پایین‌دست صورت پذیرفته است. به منظور امکان بررسی اثرات حائل نگهدارنده در فصل مشترک سد و آسفالت، سطح تماسی با استفاده از المان‌های درز با ضخامت صفر تعریف شده است. نتایج آنالیزها تصدیق می‌کند که حائل آسفالتی می‌تواند پایداری لرزه‌ای سد وزنی را در مقابله با نیروهای هیدرودینامیکی بهبود بخشد به گونه‌ای که تأثیر قابل توجه حائل آسفالتی بر توزیع مطلوب تنش‌ها در کل بدنه سد و نیز ممانعت از ایجاد تمرکز تنش و کاهش ترک‌خوردگی در قسمت شکستگی بدنه بالادست در نزدیکی تاج سد مشاهده می‌گردد و ترک‌خوردگی‌ها تنها در مقطع سطح مشترک سد و فونداسیون توسعه می‌یابند و ترک‌خوردگی در حال پیشروی در قسمت شکستگی شیب پایین‌دست به سمت بالادست بدنه سد مشاهده نگشته که به تبع آن، منتج به خرابی کل سد نمی‌گردد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Seismic Improvement of Concrete Gravity Dam Strengthened by Asphalt Buttressing

نویسندگان [English]

  • Amir Pirooznia
  • Amir javad Moradloo
Civil Engineering, Faculty of Eng., Zanjan University, Zanjan, Iran
چکیده [English]

In the present study, seismic analysis of concrete gravity dams strengthened by asphalt buttressing is presented for improving the seismic behavior of the Koyna dam in India subjected to Koyna ground motion. Fluid-Structure interaction is modeled including water compressibility and reservoir bottom absorption. The foundation is considered as rigid. A three-dimensional fixed smeared crack model is used to consider the nonlinear behavior of mass concrete. The analysis is carried out in the time domain by Newmark time integration scheme. Linear and nonlinear behavior of dam models subjected to horizontal and vertical components of selected record have been analysed. In order to investigate the effects of asphalt buttressing on the interface of dam and asphalt, the contact surface is defined using joint elements with a thickness of zero. The results of the analyzes confirm that the asphalt buttressing can improve the stability of the dam due to the pressure applied to the dam in counteracting the hydrostatic and hydrodynamic forces, Also the significant effect of asphalt Buttressing on the optimal distribution of stresses in the entire body of the dam as well as the prevention of stress concentration and reduction of fracture in the upper body near the dam crest show so that the crack at the lower section of the dam and at the interface of the dam and foundation is partially developed with a slower rate, and the cracking at the upper part near the crown of the dam does not spread to the upstream body of the dam and does not cause a total failure. Overall, it can be said that asphalt buttressing can improve the seismic stability of gravity dams by exerting pressure on the dam in opposition to hydrostatic and hydrodynamic loads.

کلیدواژه‌ها [English]

  • Asphalt Buttressing
  • Concrete gravity dam
  • Nonlinear analysis
  • Seismic Rehabilitation
  • Smeared Crack
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