مدلسازی عددی سه بعدی پاسخ گروه شمع در برابر گسترش جانبی ناشی از روانگرایی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی عمران دانشگاه تهران

2 دانش آموخته کارشناسی ارشد سازه های دریایی، دانشکده مهندسی عمران، دانشگاه تهران، تهران، ایران

چکیده

در این مقاله رفتار گروه شمع در برابر گسترش جانبی ناشی از روانگرایی با استفاده از تحلیل المان محدود سه‌بعدی همبسته خاک-آب بررسی شده است. به منظور صحت سنجی مدل عددی، از نتایج یک مدل آزمایشگاهی بزرگ مقیاس میزلرزه 1g استفاده شده است. مدل عددی با دقت قابل قبولی پاسخ خاک در میدان آزاد شامل شتاب، فشار آب حفره‌ای اضافی و جابجایی و همچنین پاسخ گروه شمع شامل جابجایی و لنگر خمشی را شبیه‌سازی نموده است. نتایج نشان می‌دهد که روانگرایی در خاک، در لحظات ابتدایی لرزش در اعماق سطحی آغاز شده و با وقوع روانگرایی، دامنه شتاب خاک کاهش یافته است. بیشترین مقدار جابجایی جانبی خاک حین گسترش جانبی در فواصل دور از شمع‌ها رخ داده و جابجایی خاک در مجاورت شمع‌ها کاهش یافته است. تغییرات لنگر خمشی در شمع‌ها با عمق و به خصوص بیشینه لنگر خمشی در شمع‌ها نیز با دقت قابل قبولی شبیه‌سازی شده است. بیشینه لنگر خمشی منفی در نزدیکی کلاهک شمع و بیشینه لنگر خمشی مثبت در نزدیکی کف مدل رخ داده و مقدار بیشینه لنگر خمشی در شمع پایین دست گروه حدود 70 %بیشتر از بیشینه لنگر خمشی در شمع بالادست می‌باشد. نتایج مطالعه پارامتری نشان می‌دهد که با افزایش سختی خمشی شمع و همچنین کاهش تراکم ماسه، میزان جابجایی و لنگر خمشی در شمع کاهش می‌یابد. دامنه شتاب تحریک بیشترین تاثیر را بر پاسخ شمع داشته به گونه‌ای که با افزایش آن به 3/5 برابر مقدار اولیه، بیشینه لنگر خمشی در شمع3/6 برابر افزایش می‌یابد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

3-Dimensional Numerical Modelling of Pile Group Response to Liquefaction-induced Lateral Spreading

نویسندگان [English]

  • Ali Kavand 1
  • Ali Sadeghi Meibodi 2
1 School of Civil Engineering, University of Tehran
2 M.Sc. Student, School of Civil Engineering, College of Engineering, University of Tehran
چکیده [English]

In this paper, a 3D coupled soil-water finite element analysis is undertaken to simulate the behavior of a pile group subjected to liquefaction-induced lateral spreading. The results demonstrate that the numerical model can satisfactorily simulate the response of soil, including its accelerations, excess pore water pressures, and displacements as well as that of the piles including displacements and bending moments. Time histories of excess pore water pressure show that liquefaction in free field soil begins at the initial stages of shaking, and upon liquefaction, the amplitude of soil acceleration decreases. The maximum lateral displacement of the ground is observed in the regions far from the piles. On contrary, the extent of ground displacement decreases in areas close to the piles. The numerical model was able to predict the bending moment profiles in piles and particularly their maximum values. The maximum negative bending moments occur nearby the pile cap, while their maximum positive values are observed at the base of the piles. Moreover, the maximum bending moment in downslope piles of the group is about 70% greater than that in upslope one. The results of the parametric study show that with increasing either the flexural stiffness of piles or the relative density of the sand, the displacement of piles decreases while the bending moment in them increases. Also, it is revealed that the amplitude of input acceleration is the most influencing factor affecting the pile response as increasing it by a factor of 3.5 induces 3.6 times greater bending moments in piles.

کلیدواژه‌ها [English]

  • Liquefaction
  • Lateral Spreading
  • Pile Group
  • Numerical Modelling
  • OpenSEES
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