بررسی آزمایشگاهی آبشستگی اطراف پایه پل با دماغه مایل

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه مهندسی آب، مرکز تحقیقات علوم آب و محیط زیست، واحد شوشتر، دانشگاه آزاد اسلامی، شوشتر، ایران.

2 عضو مرکز تحقیقات علوم آب و محیط زیست، واحد شوشتر، دانشگاه آزاد اسلامی، شوشتر، ایران.

چکیده

مقدمه و هدف: اصلی‌ترین عامل تخریب پایه پل‌ها، آبشستگی موضعی اطراف آنها می‌باشد. جهت کنترل این پدیده،‌ مطالعات بسیاری انجام شده، و راهکارهایی جهت حفاظت از پایه پل‌ها ارائه گردیده است. راهکارهای حفاظت از پایه‎های پل به دو روش مستقیم و غیرمستقیم تقسیم می‌گردند، یکی از روش‌هایی که بصورت غیرمستقیم با کمک اصلاح خطوط جریان اطراف پایه پل، می‌تواند عمق آبشستگی را کاهش دهد تغییر زاویه دماغه پل می‌باشد.
مواد و روش­ها: در این تحقیق بصورت آزمایشگاهی به بررسی تاثیر تغییر زاویه دماغه پایه پل با راستای جریان پرداخته شد. از این رو زاویه راستای برخورد جریان با دماغه پایه (α) 90 ، 85، 80، 75 و 70 درجه در شرایط آب زلال مورد بررسی قرار گرفت. در تمامی آزمایش‌ها عمق آب 10 سانتیمتر، قطر متوسط ذرات D50=0.95 mm و جهت بررسی اثر هیدرولیک جریان، سرعت‌های نسبی متفاوت در نظر گرفته شد.
یافته­ها: در بهترین حالت، پایه پل با زاویه برخورد 70 درجه توانست، در سرعت‎های کمتر از 60 درصد سرعت آستانه حرکت ذرات، 95 درصد و در سرعت‌های تا 95 درصد سرعت آستانه حرکت ذرات، به طور متوسط 36 درصد عمق آبشستگی را نسبت به پایه شاهد کاهش دهد.
بحث و نتیجه­گیری: با کاهش زاویه برخورد جریان با پایه به دلیل انحراف بخشی از خطوط جریان و عدم چرخش آنها به سمت بستر، باعث می‌گردد پتانسیل منطقه پرفشاری که در حالت پایه شاهد ایجاد گردیده، نسبت به حالتی که زاویه دماغه کاهش می‌یابد تقلیل یابد، و باعث کمتر شدن توان جریان پایین رونده و به سبب آن ضعیف شدن توان جریان‌های نعل اسبی، که عامل اصلی توسعه حفره آبشستگی هستند، ‌گردد.

کلیدواژه‌ها


عنوان مقاله [English]

Experimental Study of Scour Around Pier with Inclined Head

نویسندگان [English]

  • Mohsen Solimani babarsad 1
  • Abbas Safaei 2
1 Department of water sciences, Water Science and Environmental Research Center, Shoushtar branch, Islamic Azad University, Shoushtar, Iran.
2 Water Science and Environmental Research Center, Shoushtar branch, Islamic Azad University, Shoushtar,
چکیده [English]

Introduction:The leading cause of damages on bridge is local scouring around piers. Many studies were carried out to control and reduce this phenomenon and suggested more solution methods to protect bridge piers. Protection is divided into direct and indirect methods. In this study, to reduce scouring depth around the pier, an indirect method is used by changing the pier's head angle in a flow direction.
Materials and Methods:An experimental study on clear-water at a different angle of piers head under steady flow is presented. Experiments were used to assess the ability to change the head angle of piers to protect them. Toward this end, five angles (α) 90, 85, 80, 75, 70-degree with the flow direction were considered. The bed material size d50 was 0.9 mm and all experiments were done in Gunt hydraulic standard flume.
Findings:The results showed that the pier with a 70-degree attack angle could reduce the scour depth more than others. This happens due to diverting part of streamlines to downstream, and it can have a 36 per cent reduction overall.
Conclusion:The scouring depth and sediment point bar created around the pier with an inclined head compared with the control pier (α=90-degrees) have less scouring depth due to minor deviation of flow streamlines and reduction of disturbances around the pier.

کلیدواژه‌ها [English]

  • Scour
  • Bridge pier
  • head angle
  • incipient motion
  1. Shirole A, Holt R. Planning for a comprehensive bridge safety assurance program. Transportation Research Record. 1991;1290:3950.http://onlinepubs.trb.org/Onlinepubs/trr/1991/1290vol1/1290-005.pdf
  2. Shafaee BM, Asghari PSA. Evaluation of pier scour reduction using combination of collars, slots and threading method. Water Resources Engineering. 2018;11(37):41-52.http://wej.miau.ac.ir/article_3057.html?lang=en
  3. Chiew Y-M, Melville BW. Local scour around bridge piers. Journal of hydraulic research. 1987;25(1):15-26.https://DOI.org/10.1080/00221688709499285
  4. Breusers H, Nicollet G, Shen H. Local scour around cylindrical piers. Journal of Hydraulic Research. 1977;15(3):211-52.https://DOI.org/10.1080/00221687709499645
  5. Akhlaghi E, Babarsad MS, Derikvand E, Abedini M. Assessment the Effects of Different Parameters to Rate Scour around Single Piers and Pile Groups: A Review. Archives of Computational Methods in Engineering. 2020;27(1):183-97.https://DOI.org/10.1007/s11831-018-09304-w
  6. Chiew Y-M, Guan D, Wei M, Hsieh S-C. Characterization of horseshoe vortex in a developing scour hole at a cylindrical bridge pier. International journal of sediment research. 2019;34(2):118-24.https://DOI.org/10.1016/j.ijsrc.2018.07.001

Melville BW, Yang Y, Macky GH, Shamseldin AY. Local scour at complex bridge piers in close proximity under clear-water and live-bed flow regime. Water. 2019;11(8):1530.https://DOI.org/10.3390/w11081530

  1. Guan D, Hsieh S-C, Chiew Y-M, Low YM. Experimental study of scour around a forced vibrating pipeline in quiescent water. Coastal Engineering. 2019;143:1-11.https://DOI.org/10.1016/j.coastaleng.2018.10.010
  2. Zampieri P, Zanini MA, Faleschini F, Hofer L, Pellegrino C. Failure analysis of masonry arch bridges subject to local pier scour. Engineering Failure Analysis. 2017;79:371-
  3. 84.https://DOI.org/10.1016/j.engfailanal.2017.05.028
  4. Ettema R, Constantinescu G, Melville BW. Flow-field complexity and design estimation of pier-scour depth: Sixty years since Laursen andToch.2017.https://DOI.org/10.1061/(ASCE)HY.1943-7900.0001330
  5. Pandey M, Sharma P, Ahmad Z, Singh UK. Evaluation of existing equations for temporal scour depth around circular bridge piers. Environmental Fluid Mechanics. 2017;17(5):98195.https://DOI.org/10.1007/s10652-017-9529-9
  6. Yilmaz M, Yanmaz AM, Koken M. Clear-water scour evolution at dual bridge piers. Canadian Journal of Civil Engineering. 2017;44(4):298307.https://cdnsciencepub.com/doi/abs/10.1139/cjce-2016-0053
  7. Safaei A, Choramin M, Khajavi S, Parmoon AA, Arezoo AA. Analyzing the affective parameters on the amount of bridge scour in the vicinity of the rough
 

collar in laboratory model. WALIA journal. 2015(4):17-21.http://waliaj.com/archive/2015-2/special-issue-4-2015/

  1. Tseng MH, Yen CL, Song CC. Computation of three‐dimensional flow around square and circular piers. International journal for numerical methods in fluids. 2000;34(3):20727.https://DOI.org/10.1002/1097-0363(20001015)34:3<207::AID-FLD31>3.0.CO;2-R
  2. Johnson PA. Advancing bridge-pier scour engineering. Journal of Professional Issues in Engineering Education and Practice. 1991;117(1):48-55.
  3. Zarrati A, AR, Rezaei MJ, B Mashahir M, Zokaei M. Effect of collars and bars in reducing the local scour around cylindrical bridge piers. International Journal of Engineering.2009;22(4):33342.http://www.ije.ir/article_71812.html
  4. Melville B, Sutherland A. Design method for local scour at bridge piers. Journal of Hydraulic Engineering. 1988;114(10):1210-226.https://DOI.org/10.1061/(ASCE)0733-9429(1988)114:10(1210)
  5. Ettema R, Melville BW, Barkdoll B. Scale effect in pier-scour experiments. Journal of Hydraulic Engineering. 1998;124(6):639-42.https://DOI.org/10.1061/(ASCE)0733-9429(1998)124:6(639)
  6. Sumer B, Fredsøe J, Christiansen N, Hansen S. Bed shear stress and scour around coastal structures.  Coastal Engineering 19941995. p. 1595-609.
  7. Bozkus Z, Yildiz O. Effects of inclination of bridge piers on scouring depth. Journal of Hydraulic Engineering. 2004;130(8):827-32.https://DOI.org/10.1061/(ASCE)0733-9429(2004)130:8(827)
  8. Cai L, Gao Y-y, Qu X-c, Wang B, Zhang B-f. Numerical simulation on flow past two side-by-side inclined circular cylinders at low Reynolds number. China Ocean Engineering. 2019;33(3):34455.https://DOI.org/10.1007/s13344-019-0033-5
 

Vaghefi M, Eghbalnik L, Golbaharhaghighi MR. The Effect of Flow Conditions on Bed Topography in a 180 Degree Bend Containing 6-Inclined-Vertical Pier Groups in a Vane Perpendicular to the Flow. Modares Civil Engineering journal. 2019;19(4):1-16.https://mcej.modares.ac.ir/article-16-28029-en.html

  1. Moosaei M, Vaghefi M, Meraji S. Experimental investigation of scour pattern due to the location of twin convergent and divergent bridge piers parallel to flow in different locations of a 180 degree bend. Sharif Journal of Civil Engineering. 2018;33(4):61-70.https://DOI.org/10.24200/J30.2018.1264
  2. Vaghefi M, Akbari M, Fiouz AR. An experimental study of mean and turbulent flow in a 180 degree sharp open channel bend: Secondary flow and bed shear stress. KSCE Journal of Civil Engineering. 2016;20(4):1582593.https://DOI.org/10.1007/s12205-015-1560-0
  3. Esmaeili vm, sadati ss, Fazloula R. Experimental investigation of the bed sill effect on the temporal evolution of local scour hole around an inclined pier group on a foundation. Journal of Hydraulics. 2015;10(2):1325.https://DOI.org/10.30482/JHYD.2015.12973
  4. Raudkivi AJ, Ettema R. Clear-water scour at cylindrical piers. Journal of hydraulic engineering. 1983;109(3):338-50.https://DOI.org/10.1061/(ASCE)0733-9429(1983)109:3(338)
  5. Melville BW. Pier and abutment scour: integrated approach. Journal of hydraulic Engineering.1997;123(2):12536.https://DOI.org/10.1061/(ASCE)0733-9429(1997)123:2(125)
  6. Chiew Y-M. Mechanics of riprap failure at bridge piers. Journal of hydraulic engineering. 1995;121(9):63543.https://DOI.org/10.1061/(ASCE)0733-9429(1995)121:9(635)
  7. Melville BW, Chiew Y-M. Time scale for local scour at bridge piers. Journal of Hydraulic Engineering. 1999;125(1):59-65.https://DOI.org/10.1061/(ASCE)0733-9429(1999)125:1(59)
 

aursen EM, Toch A. Scour around bridge piers and abutments. State Library of Iowa. 1956;4:12536.http://publications.iowa.gov/id/eprint/20237

  1. Arunachalam K. Scour around bridge piers. Journal of the Indian Roads Congress. 1965;2:189-210.https://archive.org/stream/scouraroundbridg00grho/scouraroundbridg00grho_djvu.txt
  2. Shen HW, Schneider VR, Karaki S. Local scour around bridge piers. Journal of the Hydraulics Division. 1969.https://trid.trb.org/view/98453
  3. Neill CR. RIVER-BED SCOUR: A REVIEW FOR BRIDGE ENGINEERS. Canadian Good Roads Association Technical Publication.1964.https://trid.trb.org/view/97055
  4. Norman VW. Scour at selected bridge sites in Alaska. US Geological Survey, Water Resources Division. 1975;75(32-75).https://DOI.org/10.3133/wri7532

Richardson EV, Davis SR. Evaluating scour at bridges. National Transportation Library.2001.https://rosap.ntl.bts.gov/view/dot/50281