مطالعه پایداری لایه حفاظتی سنگچین در پائین‌دست حوضچه آرامش بر اساس تحلیل قابلیت اطمینان

نوع مقاله : مقاله پژوهشی

نویسنده

استادیار، دانشکده مهندسی عمران، دانشگاه تربیت دبیر شهید رجایی،تهران

چکیده

تعیین اندازه دقیق سنگچین پایدار جهت کنترل آبشستگی در پائین­دست حوضچه­های آرامش با توجه به عدم­قطعیت­های مختلف یک چالش در مهندسی هیدرولیک است که می­تواند منجر به طرحی ناایمن و یا غیر اقتصادی گردد. بر این اساس در تحقیق حاضر با استفاده از روش تحلیل قابلیت اطمینان اقدام به مطالعه پایداری سنگچین در پائین­دست حوضچه آرامش بند انحرافی کن واقع در شمال غرب شهر تهران به عنوان مطالعه موردی شد. در ادامه با استفاده از روش­های مختلف نظیر تحلیل فراوانی سیلاب، خصوصیات احتمالاتی فراسنجه­های موثر بر طراحی سنگچین تعیین شد. نتایج نشان داد که احتمال شکست سنگچین به کار رفته برای سیلاب­ 100 ساله در حدود 2/0 درصد است در حالیکه برای سیلاب 500 ساله بیش از 10 درصد می­باشد. در ادامه اقدام به بررسی ارتباط شاخص قابلیت اطمینان و ضریب ایمنی در شرایط طراحی سنگچین بر اساس مقدار میانگین فراسنجه­های موثر شد. نتایج نشان داد که این ارتباط به صورت خطی است و نیاز است که ضریب ایمنی متناظر با شاخص قابلیت اطمینان 3 β =، برابر با 1/2 باشد. در نهایت تحلیل حساسیت فراسنجه­های موثر بر پایداری سنگچین در پائین­دست حوضچه آرامش نشان داد که فراسنجه­های دبی جریان، شدت آشفتگی و چگالی نسبی سنگ بیشترین تاثیر را بر روی تغییر شاخص قابلیت اطمینان دارند.

کلیدواژه‌ها


عنوان مقاله [English]

Stability Analysis of Riprap Layer at Downstream of Stilling Basin Based on Reliability Analysis

نویسنده [English]

  • Mojtaba Karimaei Tabarestani
Assistant Professor, Civil Eng. Department, Shahid Rajaee Teacher Training University, Tehran, Iran
چکیده [English]

Determining the exact size of a stable riprap to control scouring at downstream of stilling basin is a challenge in hydraulic engineering due to various uncertainties that can lead a project become unsafe or uneconomical. Accordingly, in the present study, using the reliability analysis method, the stability of the riprap layer at downstream of the Kan diversion dam constructed at Northwest of Tehran city as a case study was studied. Then, the probabilistic properties of the parameters affecting the riprap design were determined. The results showed that the failure probability of the used riprap is about 0.2% for the 100-year flood, while it is more than 10% for the 500-year flood. Next, the relationship between reliability index and safety factor in deterministic design method calculated from the average value of effective parameters was investigated. The results showed that this relationship is linear and the safety factor corresponding to the reliability index of 3 is required to be 2.1. Finally, the sensitivity analysis of the parameters affecting the stability of the riprap layer showed that the parameters of flow discharge, turbulence intensity and relative stone density have the greatest effect on the change of the reliability index.

کلیدواژه‌ها [English]

  • stilling basin
  • scour
  • Riprap
  • Reliability analysis
  • Sensitivity analysis
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