کاهش انتشار امواج سطحی با استفاده از موانع موج متناوب مدفون متشکل از فوم و خاک

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده مهندسی عمران، دانشکدگان فنی، دانشگاه تهران، تهران، ایران

چکیده

استفاده از موانع موج یکی از روش های موثر برای کاهش اثر امواج لرزه­ای است. این موانع دارای هندسه­ های منفاوت بوده و در آرایش­ های متناوب قرار می­ گیرند. با توجه به پیچیدگی رفتار موانع موج و گستردگی آنها، تحقیقات گسترده ­ای در سال­ های اخیر برای یافتن موانع موج موثر صورت گرفته است. در این مطالعه یک مانع موج جدید برای کاهش انتشار امواج سطحی پیشنهاد می‌شود بطوریکه بر خلاف روند معمول طراحی از خاک دست نخورده در مرکز مانع و یک لایه فوم به‌عنوان مصالح نرم در دو طرف آن استفاده می­ شود. در ابتدا با استفاده از مفاهیم فیزیک حالت جامد و تئوری‌های مربوط به ساختارهای متناوب مانند تئوری بلاخ-فلوکه و با استفاده از نرم ­افزار اجزا محدود  COMSOL، مانع موج در یک شبکه متناوب نامحدود بررسی شده و سپس با تغییر بردار موج در ناحیه اول بریلوئن و به دست آوردن فرکانس‌های ویژه، نمودار پراکندگی رسم می‌شود. با رسم نمودار پراکندگی، شکاف باند متناظر با این سلول واحد به‌ دست می‌آید. از آنجا که در واقعیت امکان ساخت شبکه نامحدود از موانع موج وجود ندارد، یک شبکه محدود از موانع موج مدلسازی شده و نتایج آن با حالت ایده آل شبکه بی نهایت مقایسه می ­شود. رفتار شبکه محدود هم در حوزه فرکانس و هم در حوزه زمان بررسی شده است. نتایج به دست آمده نشان می­دهند که مانع موج متشکل از خاک و فوم با ارتفاع چهار متر، توانایی بسیار خوبی در کاهش امواج در شبکه های نامحدود و محدود دارند و شکاف باند به دست آمده بین  Hz12/75 تا Hz 17/61 هرتز است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Surface waves attenuation using periodic buried soil-foam wave barriers

نویسندگان [English]

  • Kourosh Gholami
  • Reza Rafiee-Dehkharghani
School of Civil Engineering, College of Engineering, University of Tehran, Tehran, IRAN
چکیده [English]

Using wave barriers is one of the effective measures for seismic wave attenuation. The barriers have different geometries and are arranged in periodic configurations. Considering the complex barrier behaviors and their miscellaneous characteristics, much research has been conducted in recent years to find effective barriers. This paper proposes a new unit cell as a wave barrier to reduce the propagation of surface waves. Unlike the common practice in which harder and heavier materials are placed in the center and soil around it, the suggested unit cell consists of undisturbed soil as a core and a foam layer on both sides as a soft coating material. Firstly, a unit cell is considered in an infinite periodic lattice using solid-state physics concepts and periodic theories and is modeled using COMSOL Multiphysics FEM software. The dispersion curve can be obtained by changing the wave vector in the first irreducible Brillouin zone and calculating the corresponding eigenfrequencies. Then, the bandgaps are defined in the dispersion curves. Following that, because constructing an infinite lattice is impractical, a finite lattice of the unit cell is simulated to explore the unit cell efficiency in a more realistic setting. The time and frequency domain analyses are carried out using the finite lattices. The findings reveal that the proposed soil-foam unit cell with a height of four meters can effectively reduce the waves in the bandgap range in infinite and finite lattices. The obtained bandgap range is between 12.75 to 17.61 Hz.

کلیدواژه‌ها [English]

  • Wave barrier
  • surface waves
  • periodic lattice
  • Bloch-Floquet theory
  • Finite element method
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