تحلیل همبسته دینامیکی شمع‌های فولادی قطور واقع در لایه‌های خاک روانگرا

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی عمران و محیط زیست، دانشگاه تربیت مدرس، تهران، ایران

2 دانشکده فنی و مهندسی، دانشگاه شهرکرد، شهرکرد، ایران

چکیده

بسیاری از سواحل ایران در معرض خطر زلزله قرار دارند و تحت اثر بارگذاری دینامیکی زلزله، این خاک‌ها با توجه به اشباع بودن، مستعد روانگرا شدن هستند. لذا در تحقیق حاضر، رفتار خاک ماسه‌ای اشباع در دو لایه با تراکم نسبی‌های مختلف به همراه اثرات اندرکنشی خاک و شمع تحت اثر بار دینامیکی سینوسی از نوع تاریخچه شتاب مورد توجه قرار گرفته است. بدین منظور از یک مدل رفتاری بر مبنای نظریه صفحات تودرتو استفاده گردیده و برای حل معادلات حاکم بر محیط مختلخل اشباع به صورت کاملاً همبسته، از روش اجزای محدود استفاده شده است. بر اساس نتایج به دست آمده، ملاحظه می ­شود در لایه ­های سطحی با پتانسیل روانگرایی بالا، بدون توجه به اینکه فرکانس بارگذاری چه مقداری باشد، در این اعماق روانگرایی رخ خواهد داد. اما در اعماق و لایه ­هایی که پتانسیل روانگرایی در آن‌ها کمتر است، افزایش فشار آب حفره­ای به شدت تابع فرکانس بارگذاری است، به طوری که با افزایش فرکانس نسبت به فرکانس طبیعی، فشار آب حفره­ای تحت بارگذاری دینامیکی، کمتر افزایش می ­یابد. همچنین، بر اساس تحلیل ­های انجام شده تحت فرکانس‌های مختلف مشاهده می‌شود که در یک فرکانس خاص بارگذاری دینامیکی، افزایش طول شمع تأثیر چندانی بر تغییر مکان سر شمع (به دلیل جرم زیاد آن) ندارد اما می‌تواند تغییر مکان در طول و انتهای مدفون شمع را تا حد زیادی تحت تأثیر قرار دهد. از این رو، هر چه نسبت طولی از شمع که در خاک روانگرا قرار دارد به طول کل شمع، بزرگتر باشد، امکان تغییر مکان انتهای مدفون شمع بیشتر می­ شود؛ و در نتیجه می‌تواند منجر به عدم پایداری سازه شود.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Dynamic coupled analysis of large-diameter steel piles located in liquefiable soil layers

نویسندگان [English]

  • Amin Ghotbi 1
  • Mohammad Oliaei 1
  • Heisam Heidarzadeh 2
1 Postgraduate student, Faculty of Civil & Environmental Engineering, Tarbiat Modares University, Iran
2 Assistant Professor of Civil Engineering, Faculty of Engineering, Sharekord University, Iran
چکیده [English]

Many shores in Iran are at risk of earthquakes, and due to the dynamic loading of the earthquake, these saturated soils are prone to liquefaction. In this study, the behavior of two-layered saturated sand with different relative densities and the interaction effects of soil and pile under dynamic loads has been considered. For this purpose, a constitutive model presented in the multi-surface framework has been applied. In addition, the equations governing the saturated environment have been solved in a completely coupled way based on the finite element method. According to the obtained results, liquefaction will occur in the upper layers no matter the loading frequency when their liquefaction potential is high. Nevertheless, at depths and layers where the liquefaction potential is low, the pore pressure is strongly dependent on the loading frequency, so with an increase in the frequency of the dynamic loads, the water pore pressure increases less. Also, based on the analyses performed under different frequencies, it is observed that at a dynamic loading frequency, increasing the pile length has little effect on the displacement of the pile head but can significantly affect the displacement of the buried parts. Therefore, the larger the ratio of the pile length in the liquefiable soil to the total length of the pile, the greater the possibility of more displacement in the buried end of the pile; and as a result, it can lead to instability of the structure.

کلیدواژه‌ها [English]

  • Numerical modeling
  • Liquefaction
  • Layered soil
  • Soil-pile interaction
  • Multi-surface constitutive model

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نشریه مهندسی عمران امیرکبیر
دوره 54، شماره 11
بهمن 1401
صفحه 4271-4286

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