پاسخ لرزه‌ای سطح تپّه‌ی آبرفتی ذوزنقه‌ای واقع بر حفره‌ی دایره‌ای: موج مهاجم قائم SH

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه مهندسی عمران، واحد زنجان، دانشگاه آزاد اسلامی، زنجان، ایران

2 گروه مهندسی عمران، واحد زنجان، دانشگاه آزاد اسلامی، زنجان، ایران.

چکیده

در این مقاله به تحلیل لرزه‌ای سطح تپّه‌ی آبرفتی ذوزنقه‌‌ای واقع بر یک حفره‌ی دایره‌ای زیرزمینی در برابر امواج مهاجم قائم SH پرداخته شده است. بدین منظور، از روش عددی اجزای مرزی نیم‌صفحه در حوزه‌ی زمان برای تهیّه‌ی مدل پیشنهاد شده بهره گرفته شده است. از جمله مهم‌ترین قابلیت‌های این روش، تمرکز مش‌ها صرفاً بر روی مرز عارضه‌ی مورد نظر می باشد. بر‌این‌اساس و مبتنی بر فرآیند زیرسازه‌سازی، ابتدا مدل ناهمگن مزبور به یک نیم‌صفحه‌ی حفره‌دار و یک تپّه‌ی سطحی تفکیک شده و سپس ماتریس‌های حاصل با اقناع شرایط پیوستگی/مرزی، سرهم‌سازی می‌شوند. پس از پیاده‌سازی روش پیشنهاد شده در توسعه‌ی الگوریتم داس‌بِم، چند مثال پیرامون صحّت و سقم آن مورد تحلیل قرار گرفته و پاسخ‌های بدست آمده با نتایج سایر محققان مقایسه شده است. در ادامه، با در نظر گرفتن پارامترهای کلیدی نسبت‌ امپدانس و شکل، پاسخ لرزه‌ای سطح تپّه در دو حوزه‌ی زمان و فرکانس حساسیّت‌سنجی شده است. در این میان، تأثیر حضور حفره‌ی زیرزمینی نیز در الگوی بزرگنمایی سطح مطالعه شده است. نتایج نشان داد نسبت‌های امپدانس و شکل تپّه‌ی ذوزنقه‌ای در حصول الگوی پاسخ بسیار مؤثر می‌باشد بگونه‌ای که افزایش نسبت شکل تپّه و متناظر آن کاهش تقابل امپدانس، مسبب تشدید حالت بحرانی پاسخ حوزه‌ی زمان و فرکانس گردید. همچنین، حداکثر بزرگنمایی در بیشینه‌ی نسبت شکل و کمینه‌ی امپدانس حاصل شد. این تحقیق در محور موضوعی ژئوتکنیک لرزه‌ای ارائه شده و نتایج آن از دیدگاه کاربردی در تکمیل و تدقیق آئین‌نامه‌‌های لرزه‌ای موجود قابل استفاده می‌باشد.

کلیدواژه‌ها


عنوان مقاله [English]

Seismic response of the trapezoidal alluvial hill located on a circular cavity: Incident SH-wave.

نویسندگان [English]

  • Mehdi Panji 1
  • Saeed Mojtabazadeh-Hasanlouei 2
  • Mohammad Habibivand 2
1 Department of Civil Engineering, Islamic Azad University, Zanjan, Iran.
2 Department of Civil Engineering, Zanjan Branch, Islamic Azad University, Zanjan, Iran.
چکیده [English]

A direct time-domain numerical approach named the half-plane boundary element method is proposed based on the half-space Green’s functions for seismic analysis of trapezoidal alluvial hill located on a circular cavity, subjected to propagating vertical incident SH-waves. To analyze the assumed model, a half plane time-domain Boundary Element Method (BEM) was used which can concentrate the meshes only around the boundary of desired features. First, the problem is decomposed into two parts including a pitted half-plane and a trapezoidal filled solid on the surface. Then, the influence coefficients of the matrices are obtained by applying the method to each part. By satisfying the boundary/continuity conditions on the interfaces, a coupled equation is formed to determine unknown boundary values in each time-step. After implementing the method in an advanced developed algorithm, its efficiency is investigated by solving some practical examples and compared with those of the published works. To complete the results, the sensitivity analysis was carried out to obtain the seismic response of hill by considering the key parameters including impedance and shape ratios. In the meantime, the effect of subsurface cavity on the amplification pattern of surface has been studied as well. The results showed that the impedance and shape ratios of the trapezoidal alluvial hill were very effective on the seismic response of surface. The results of the present study can be used by geotechnical engineers to completing and increasing the accuracy of existing codes around the subject of ground surface zonation in presence of different topographic features.

کلیدواژه‌ها [English]

  • Circular cavity
  • Half-plane BEM
  • SH-wave
  • Trapezoidal hill
  • Time-domain
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