مطالعه عددی و آزمایشگاهی بر روی رفتار لرزه‌ای خاک میخ کوبی شده به منظور ارائه ضریب شبه استاتیکی بر اساس سطوح عملکرد

نوع مقاله : مقاله پژوهشی

نویسنده

گروه عمران، دانشکده فنی و مهندسی دانشگاه آزاد اسلامی، واحد علوم و تحقیقات، تهران، ایران

چکیده

با توجه به گسترش استفاده از روش طراحی بر مبنای عملکرد لرزه‌ای در میان سازه‌های ژئوتکنیکی طی دو دهة اخیر و محروم ماندن سیستم‌های میخ کوبی از این توسعه، در این تحقیق کوشش شده است تا ضریب شبه استاتیکی به عنوان تابعی از پارامترهای اصلی زلزله، ویژگیهای ژئوتکنیکی در قالب شرایط ساختگاهی و سطوح عملکرد دیوار میخ کوبی شده معرفی گردد. به این منظور، با استفاده از آزمایشات میز لرزه بر روی مدل فیزیکی سیستم میخ کوبی به تعیین مرز‌های سطوح عملکرد این سیستم در شرایط لرزه‌ای و هندسی مختلف پرداخته شده است. سپس با تکیه بر نتایج حاصل از مدلسازی عددی سیستم میخ کوبی در قالب تغییر شکل‌های ماندگار و تعیین ضریب شبه استاتیکی معادل هر یک از مدلهای‌های عددی مورد مطالعه با استفاده از آنالیزهای تعادل حدی، به ارائة ضریب شبه استاتیکی معادل با سطوح عملکرد پرداخته شده است. نتایج حاصل در قالب تقسیمات ساختگاهی و لرزه‌ای مطابق با آیین‌نامه 2800 ایران و بصورت مجزا ارائه شده است که بیانگر تأثیر چشمگیر نوع ساختگاه و شرایط لرزه‌ای بر انتخاب ضریب شبه استاتیکی معادل با سطوح عملکرد می‌باشد. از سوی دیگر، سطح گسیختگی مشاهده شده در این سیستم یک سطح گسیختگی منحنی‌الخط با نقطة عطف مشخص می باشد به نحوی که مکان هندسی آن به عنوان تابعی از طول میخ‌ها تعریف می‌شود. همچنین، صرف نظر از طول میخ‌های مختلف، مقادیر x/H = 0/5%∆ بعنوان مرز وقوع تغییر شکلهای پلاستیک و مقادیر x/H = 3/75%∆ به عنوان مرز تشکیل گوه گسیختگی و وقوع تخریب برای سیستم میخ کوبی مشاهده شد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Numerical and Experimental Study on Seismic Behavior of Soil-Nailed Walls to Introduce the Pseudo Static Coefficient Based on Performance Levels

نویسنده [English]

  • M. Yazdandoust
Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
چکیده [English]

This study, tries to suggest a design method based on displacement using experimental and numerical modeling in soil nailed walls. In this case, dynamic loading characteristics, geometrical characteristics of reinforced soil mass and type of the site are considered to introduce the pseudo static coefficient as a function of seismic performance level and dynamic loading characteristics. For this purpose, the influence of dynamic loading characteristics, reinforcement length, height of reinforced system and type of the site are investigated on seismic behavior of soil nailed wall by numerical analysis. Furthermore, the performance levels of this structure were determined by experimental studies of shaking table tests. The results illustrate that the seismic response of this type of wall is highly dependent to cumulative absolute velocity, maximum acceleration, height and reinforcement length. The results also indicate that the use of coefficients in this study leads to most efficient designs in comparison with other methods which are generally suggested in codes that are usually based on limit-equilibrium concept. The outputs show the over-estimation of equilibrium design methods in comparison with proposed displacement based methods here. The pattern of the observed failure mechanisms included a moving block and a parabolic failure surface with certain inflection point. Also, irrespective of different nail lengths, a range of Δx/H = 0.5 % as a transitional level from quasi-elastic to plastic state and based on starting the development of active wedge failure, a range of Δx/H = 3.75% as a transitional level from plastic to failure state were determined.

کلیدواژه‌ها [English]

  • Soil-Nailed Wall
  • seismic performance
  • Pseudo Static Coefficient
  • Seismic Levels
  • Dynamic Failure Mechanism

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نشریه مهندسی عمران امیرکبیر
دوره 50، شماره 1
فروردین و اردیبهشت 1397
صفحه 189-210

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