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

مراجع

Elnikhely, E. (2017). Investigation and analysis of scour downstream of a spillway. Ain Shams Engineering Journal. DOI: 10.1016/j.asej.2017.03.008.
Farhoudi, J. and Helbar, S. M. (2010). Design of Stable Riprap Downstream of Stilling Basins Using Froude Number. Journal of Water and Soil Science. 19(1), 97-106. (In Farsi)
Halder, A. and Mahadevan, S. (2000). Probability, Reliability and Statistical Methods in Engineering Design. John Wiley & Son, New York.
Hydraulic Engineering Circular No. 14 (HEC No.14). (2006). Hydraulic Design of Energy Dissipaters for Culverts and Channels. Federal Highway Administration. Report No. FHWA-NHI-06-086.
Iran Ministry of Energy. Report No. 316. (2005). Guideline for Determination Design flood return period in river works. Iran Water Resources Management Co.P.18.
Johnson, P. A. and Dock, D. A. (1998). Probabilistic Bridge Scour Estimates. Journal of Hydraulic Engineering, 124(7), 750-754.
Karimaei Tabarestani, M. and Zarrati, A. R. (2019). Reliability analysis of riprap stability around bridge piers. Journal of Applied Water Engineering and Research. 7 (1), 79-88.
Karimaei Tabarestani, M., Salamatian, A. and Panahi Azad, M. (2020a). Component and system-level reliability analysis of riprap layer around bridge pier in clear water condition. ISH Journal of Hydraulic Engineering. DOI: 10.1080/09715010.2019.1711206.
Karimaei Tabarestani, M., Feizi, A. and Bali, M. (2020b). Reliability-based design and sensitivity analysis of rock armors for rubble-mound breakwater. Journal of the Brazilian Society of Mechanical Sciences and Engineering. 42(3): 1-13.
Karimaei Tabarestani, M. (2020). Study on stability and sensitivity analysis of protective riprap layer placed around bridge pier by using reliability analysis theory. Journal of Hydraulics. 14(4):51-68. (In Farsi)
Champagne, T., Barlock, R., Ghimire, S., Barkdoll, B., Gonzalez-Castro, J. and Deaton, L. (2017). Scour Reduction by Air Injection Downstream of Stilling Basins: Optimal Configuration Determination by Experimentation. Journal of Irrigation and Drainage Engineering. 04016067-1-9.
Maynord, S. T. (1987). Stable riprap for open channel flows. Ph. D dissertation, Department of Civil Engineering, Colorado State University, Ft Collins, CO.
Muzzammil, M., Siddiqui, N. A. and Siddiqui, A. F. (2008). Reliability considerations in bridge pier scouring. Journal of Structural Engineering and Mechanics. 28(1): 1-18.
Nowak, A. S. and Collins, K. R. (2000). Reliability of structures. McGraw Hill, Singapore.
Novak, P., Moffat, A.I.B., Nalluri, C. and Narayanan, R. (2007). Hydraulic structures. 4th Edition. Taylor & Francis.
Oliveto, G. and Comuniello, V. (2008). Local Scour Downstream of Positive-Step Stilling Basins. Journal of Hydraulic Engineering. 135(10), 846-851.
Oliveto, G. (2012). Local scouring downstream of a spillway with an apron. ICE Water Management, 166 (WM5) 254-261.
Pilarczyk, K. W. (1990). Stability criteria for revetments. In: Proceeding of National Conference on Hydraulics Engineering, American Society of Civil Engineering (eds.) HH Chang and JC Hill, San Diego, USA. 15-26.
Rackwitz, R. and Fiessler, B. (1976). Note on Discrete Safety Checking When Using Non-Normal Stochastic Models for Basic Variables. Load Project Working Session. Cambridge, MA: MIT.
Saber, M. and Ghodsian, M. (2020). Experimental Investigation on Scour Downstream of USBR VI Stilling Basins. Journal of Hydraulics, 14 (4): 138-148. (In Farsi)
Salamatian, S. A., Zarrati, A. R. and Banazadeh, M. (2013). Assessment of bridge safety due to scour by Bayesian network. Journal of Water Management. 166(6), 341–350.
Shafai Bajestan, M. and Omidi, S. (2016). Investigation of Scour Depth Downstream of Stilling Basin for the Case of B-Jump. Irrigation Sciences and Engineering. 38(4), 125-136. (In Persian)
Taebi, H., Fathi, M. and Shafai Bajestan, M. (2011). Prediction of stable riprap size to control scouring at downstream of stilling basin. Iranian Water Research Journal. 5(8): 23-34. (In Farsi)
Tehran Technical and Engineering Consulting Organization (TTECO). (2011). Hydraulic design report of Kan diversion dam. Report No. CAL-STP-R-DVD-ST-BD-001.
United States Army Corps of Engineers(USACE). (1997). Engineeringand design: Introduction to probability and reliability methods for usein geotechnical engineering. Engineering Circular No.  1110-2-547. Dept. of the Army. Washington D.C.
Vahidi Alvar, M., Asghari Pari, S. A., Shafai Bajestan, M. and Arman, N. (2020). Investigating the causes of scouring downstream of stilling basin of Shohada diversion dam and proposing suitable solutions to control it. Irrigation Sciences and Engineering. 43(1), 1-14. (In Farsi)
تحقیقات آب و خاک ایران
دوره 52، شماره 4
تیر 1400
صفحه 1163-1177

فایل ها

هم رسانی

ارجاع به این مقاله

آمار