بررسی اثر پارامترهای هندسی گروه شمع بر سرعت بحرانی خط ریلی قطار سریع‌السیر (مطالعه موردی: خط ریلی قطار سریع‌السیر تهران- اصفهان)

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی عمران- دانشگاه علم و صنعت ایران

2 علم و صنعت- مهندسی راه آهن

3 دانشکده مهندسی معدن- دانشگاه آزاد اسلامی (واحد علوم و تحقیقات)

10.22034/tri.2021.263446.2848

چکیده

یکی از چالش‌های موجود در خط ریلی سریع‌السیر تهران- اصفهان، محدوده عبوری از دریاچه نمک استان قم است که با توجه به وجود خاک بسیار نرم و بالا بودن تراز آب زیرزمینی در این محدوده، نشست‌های قابل توجهی در اثر عبور قطار سریع‌السیر ایجاد می‌شود که به منظور کنترل نشست‌ها، شمع‌های بتنی درجاریز در بستر خاکی اجرا خواهد شد. اما با توجه به سرعت بالای قطار در این مسیر و وجود بستر نرم، علاوه بر مشکل نشست، انتظار می‌رود که پدیده تشدید نیز رخ دهد. علیرغم تحقیقاتی که تاکنون بر روی اثر بهسازی بستر خاکی نرم با شمع بر روی مقدار سرعت بحرانی که منجر به وقوع پدیده تشدید می‌شود، انجام شده است، همچنان ابهاماتی در خصوص تاثیر و یا عدم تاثیر اجرای شمع بر روی مقدار سرعت بحرانی مسیر ریلی وجود دارد. لذا در پژوهش پیش رو، ابتدا با مدل‌سازی عددی شمع منفرد و مقایسه نتایج آن با داده‌های بدست آمده از آزمایش بارگذاری فشاری استاتیکی در محل، ظرفیت باربری شمع و مشخصات فیزیکی و مکانیکی لایه‌های خاک در محل بدست آمده و سپس مسیر ریلی در محدوده مذکور با استفاده از مدل سه بعدی اجزاء محدود تحت سرعت‌های عبوری مختلف قطار (از سرعت km/h 60 الی km/h 450) مورد تحلیل و بررسی قرار گرفته و مقدار سرعت بحرانی مسیر تعیین گردیده است که نتایج نشان‌دهنده وقوع پدیده تشدید در سرعت km/h 100 معادل سرعت موج رایلی لایه اول خاک بستر است. سپس به منظور بررسی تاثیر اجرای گروه شمع در بستر نرم بر روی مقدار سرعت بحرانی مسیر، آرایش هندسی مختلف گروه شمع با تغییر فواصل افقی شمع‌ها از D5 (D= قطر شمع) الی D2 تحلیل شده است که نتایج نشان‌دهنده تاثیر بهسازی بستر نرم با شمع‌های بتنی بر افزایش مقدار سرعت بحرانی است؛ به نحوی که مقدار سرعت بحرانی به سرعت km/h 250 افزایش پیدا کرده است.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Three- dimensional numerical simulation of the Geometrical Dimension pile group effects on the critical speed of high- speed track railway (Case Study: Tehran- Isfahan high speed track railway)

نویسندگان [English]

  • morteza sabbaghi 1
  • morteza Esmaeili 2
  • Mahdi kharghani 3
1 Civil Engineering Faculty- Iran University of Science and Technology
2 Railway Faculty- Iran University of Science and technology
3 Department of Mining Engineering, Science and Research Branch, Islamic Azad University
چکیده [English]

Existence of soft soil layers and high ground water level in the Qom Salt Lake area have caused deflection more than allowable limitation in Tehran- Isfahan high speed track railway. Due to reduce deflection of track railway in this area, improving the stiffness and strength of the soil beneath will be done by means of concrete pile group. But also, due to the high speed of train, resonance phenomenon is expected to happen. Despite conducting some researches on the effect of improving soft ground by pile in recent years, but there are ambiguities about performance of pile on the increasing critical speed of the track-ground system which track has been experienced large dynamic amplification as the train speed approaches that speed. So first, the bearing capacity of pile and soil layers geotechnical parameters have been determined by comparing the numerical modeling results of single pile with data obtained from in situ compressive loading test on that in this paper. Afterwards, the effect of the geometrical dimension pile group on the dynamic behavior and critical speed of track-ground system has been investigated under various speed of train (60-450 km/h) using 3D finite element model. The results indicate that resonance phenomenon has been occurred at speed of 100 km/h, which is equal to Rayleigh speed of first subgrade layer. However, improving of soil layers by pile group increases the value of the critical speed to 250 km/h.

کلیدواژه‌ها [English]

  • Dynamic Behavior
  • critical speed
  • High Speed Railway Track
  • Pile Group
  • 3D finite element model

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