پیشنهاد معیار گسیختگی ژئوتکنیکی ریزشمع‌های خودحفار بر اساس نتایج آزمایش‌های بارگذاری استاتیکی تمام مقیاس

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه مهندسی عمران، دانشگاه قم، قم، ایران

2 مهندسی عمران، دانشگاه قم

چکیده

دردهه اخیر استفاده از ریزشمع‌های خودحفار افزایش چشم‌گیری داشته است. این ریزشمع‌ها باتوجه به روش اجرا، زمان و هزینه را کاهش داده و علاوه بر تسلیح خاک، همزمان سبب به‌سازی خاک نیز می‌گردند. باوجود افزایش استفاده از این ریزشمع‌ها، مطالعات اندکی درخصوص عملکرد آنها خصوصا تعیین ظرفیت باربری، تدوین معیارهای گسیختگی و تفسیر آزمون‌های بارگذاری صورت گرفته است. در این تحقیق 22 ریزشمع خودحفار با روش تزریق همزمان در طول ها و خاک های متفاوت اجرا و آزمون‌های بارگذاری کششی و فشاری تمام مقیاس بر روی آنها انجام شده است. سپس با استفاده از شش معیار گسیختگی متداول در ارزیابی باربری شالوده های عمیق، به تشریح عملکرد و ظرفیت باربری این نوع ریزشمع‌ها پرداخته شده‌است. درادامه با استفاده از روابط ریاضی و فرضیات موجود در خصوص منحنی‌های بارگذاری- جابجایی و همچنین با استفاده از مدل‌سازی عددی منحنی های بار-نشست، نتایج آزمایش میدانی تا حد گسیختگی ژئوتکنیکی توسعه داده شده است. نتایج نشان می‌دهد از آنجا که قطر و مقاومت باند حاصل در ریزشمع های خودحفار بیش از فرضیات تئوری می‌باشد، معیارهای گسیختگی موجود برای تفسیر نتایج بارگذاری ریزشمع‌های خودحفار مناسب نبوده و افزایش مقاومت جداره و کاهش طول الاستیک را درنظر نمی‌گیرند. براین اساس با استفاده از اطلاعات به دست آمده از اعمال معیارهای گسیختگی، توسعه نتایج آزمایش‌های بارگذاری و بررسی اثر کوتاه شدگی الاستیک در آزمون بارگذاری، رابطه‌ای جهت تعیین بارگسیختگی ریزشمع‌های خودحفار مبتنی بر روش متعارف دیویسون ارائه شده است.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

A New Failure Criteria for Hollow-bar Micropile Based on Full-Scale Static Load Tests

نویسندگان [English]

  • Mohammadali Fakharnia 1
  • hamed bayesteh 2
1 Department of civil engineering, University of Qom, Qom, Iran
2 Department of civil engineering, university of Qom
چکیده [English]

Recently, the use of hollow-bar micropiles has increased rapidly. These micropiles reduce the time and cost and not only were used as a reinforcement element but also used to improve the surrounding soils. Despite the increasing use, few studies have been conducted on the performance of this type of micropiles, in particular the determination of load capacity, failure criteria, and interpretation of loading tests. In this study, 22 hollow bar micropiles with simultaneous injection methods in different lengths and soils were executed and full-scale tension and compression loading tests were performed on them. Then, by using the six common failure criteria for pile foundation, the performance and ultimate load of these tests were evaluated. Using mathematical relations, assumptions about load-displacement curves and using numerical modeling of the observed load-displacement behavior, field test results have been developed to reach the geotechnical failure. The results show that since the diameter and bond strength of hollow bar micropiles is more than theoretical ones, the existing failure criteria are not suitable for interpretation of their load-deformation behavior. The existing failure criteria do not take into account the increase in the bond strength and the reduction of the elastic length. Based on the information obtained from the existing failure criteria and considering the effect of elastic shortening on the loading test results, a failure criterion has been proposed to determine the failure load of hollow bar micropile based on the Davison method.

کلیدواژه‌ها [English]

  • Hollow bar micropile
  • Static load test
  • Failure criteria
  • Full scale

مراجع

[1]O.F.E.H. Drbe, M.H. El Naggar, Axial monotonic and cyclic compression behaviour of hollow-bar micropiles, Canadian Geotechnical Journal, 52(4) (2014) 426-441.
[2]S.B. Mickovski, F.M. Lindsay, M.J. Smith, Construction and testing of self-drilled soil nails, Proceedings of the Institution of Civil Engineers-Geotechnical Engineering,169(6) (2016)541-553.
[3]A. Phear, C. Dew, B. Ozsoy, N. Wharmby, J. Judge, A. Barley, Soil nailing-best practice guidance, Ciria, London, UK, (2005).
[4]J. Bishop, H. Aschenbroich, B. DeBernar, Class I and II micropiles with hollow-bar reinforcement load tests and performance measurements, in:  Proceedings of the 7th International Workshop on Micropile, Schrobenhausen, Germany, (2006), pp. 3-7.
[5]J.E. Gomez, C.J. Rodriguez, H.D. Robinson, J. Mikitka, K. L., Hollow core bar micropiles—installation, testing, and interpolation of design parameter of 260 micropiles, in:  In Proceedings of the 8th International Workshop on Micropiles, Toronto, Ont., (2007).
[6]J. Bennett, N. Hothem, Hollow bar micropiles for settlement control in soft clay, in:  Proceedings of the 10th International Workshop on Micropiles, Washington, DC, (2010).
[7]J. Bruce, N. Gurpersaud, Grout Flushed Micropiles Foundations for a New Rail Overpass, in:  Proceedings of the 9th International Workshop on Micropiles, London, England, (2009).
[8]W. Telford, M. Kokan, H. Aschenbroich, Pile load tests of Titan Injection Bored micropiles at an industrial plant in North Vancouver, in:  Proceedings of the 9th International Workshop on Micropiles,, London, UK, (2009).
[9]A.Y. Abd Elaziz, M.H. El Naggar, Geotechnical capacity of hollow-bar micropiles in cohesive soils, Canadian Geotechnical Journal, 51(10) (2014) 1123-1138.
[10]A.Y. Abd Elaziz, M.H. El Naggar, Group behaviour of hollow-bar micropiles in cohesive soils, Canadian Geotechnical Journal, 51(10) (2014) 1139-1150.
[11]A.Y. Abd Elaziz, M.H. El Naggar, Performance of hollow bar micropiles under monotonic and cyclic lateral loads, Journal of Geotechnical and Geoenvironmental Engineering, 141(5) (2015) 04015010.
[12]A.Y. Abd Elaziz, M.H. El Naggar, Axial behaviour of hollow core micropiles under monotonic and cyclic loadings, Geotechnical Testing Journal, 35(2) (2012)249-260.
[13]H. Lahuta, J. Aldorf, E. Hrubesova, H. Rubisarova, A. Janicek, Influence of Buckling at the Rod Micropiles, Procedia engineering, 142 (2016) 328-333.
[14]H. Bayesteh, M. Sabermahani, Full-Scale Field Study on Effect of Grouting Methods on Bond Strength of Hollow-Bar Micropiles, journal of Geotechnical and Geoenvironmental Engineering, 144(12) (2018).
[15]F. BengtH, The analysis of results from routine pile load tests, Ground Engineering, 13(6) (1980) 19-31.
[16]B.H. Fellenius, Basics of foundation design, Electronic Edition,  January 2017 ed., Lulu. com, (2017).
[17]C.W. Ng, T.L. Yau, J.H. Li, W.H. Tang, New failure load criterion for large diameter bored piles in weathered geomaterials, Journal of Geotechnical and Geoenvironmental Engineering, 127(6) (2001) 488-498.
[18]ASTM-D1143, Standard Test Method for Piles Under Static Axial Compressive Load, in, American Society for Testing and Materials, New York, (1994), pp. 104-114.
[19]ASTM-D3689, Standard Test Method for Individual Piles Under Static Axial Tensile Load, in, American Society for Testing and Materials, New York, (2007), pp. 416-426.
[20]FHWA(Federal Highway Administration), Micropile design and construction—Reference manual, FHWA NHI-05-039, US Department of Transportation, McLean, VA (2005) 436.
[21]DFI, Guide to Drafting a Specification for Micropiles, in:  Deep Foundations Institute, The International Association of Foundation Drilling, New Jersey, (2004), pp. 60 pages.
[22]F.K. Chin, Estimation of the ultimate load of piles from tests not carried to failure, in:  Proc. 2nd Southeast Asian Conference on Soil Engineering, Singapore, (1970).
[23]J. Brinch Hansen, Discussion of Hyperbolic Stress-Strain Response: Cohesive Soil. by Robert L. Kondner, J. Soil Mech., Found. Div., ASCE, 89(4) (1963) 241-242.
[24]L. Decourt, Behavior of foundations under working load conditions, 11th Pan-American Conferenvce on Soil Mechanics and Geotechnical Engineering, Foz do Iguaçu, 4 (1999) 453-488.
[25]L. Décourt, Loading tests: interpretation and prediction of their results, in: D.K.C. J.E. Laier, and M.H. Hussein (Ed.) From Research to Practice in Geotechnical Engineering, Geotechnical Special Publication, GSP 180, (2008), pp. 452-488.
[26]M. Davisson, High capacity piles, Proc. of Lecture Series on Innovations in Foundation Construction, 52 (1972) 81-112.
[27]H. Butler, H. Hoy, The texas quick load test method for foundation load testing–users manual, FHWA IP-77.8, FHWA Implementation Division, Washington, DC,  (1977).
[28]F.M. Fuller, H.E. Hoy, Pile load tests including quick-load test method, conventional methods, and interpretations, Highway Research Record, (333) (1970) 74–86.
[29]O.F. Drbe, Investigation of Hollow Bar Micropiles in Cohesive Soil, A thesis submitted in partial fulfillment of the requirements for the degree in Master of Engineering Science,Western University, (2013).
[30]Canadian Geotechnical society (CGC), Canadian foundation engineering manual, 4th ed, Bitech Publishers, Richmond, Canada,  (1995).
[31]BOD, Pile foundations, Prac. Note for Authorised Persons and Registered Struct. Engrs., No. 66, 1997 Revision, Buildings Department, Hong Kong,  (1997).
[32](NYSDOT) State of New York Department of Transportation, Standard Specifications,Albany.New York,12232, (2008).
[33]F.H. Kulhawy, P.W. Mayne, Manual on estimating soil properties for foundation design, Electric Power Research Inst., Palo Alto, CA (USA); Cornell Univ., Ithaca, NY (USA). Geotechnical Engineering Group,(1990).
[34]S.-S. Jeon, Interpretation of load tests on minipiles, Proceedings of the Institution of Civil EngineersGeotechnical Engineering, 157(2) (2004) 85-90.
[35]J.E. Bowles, Y. Guo, Foundation analysis and design, McGraw-hill New York, (1996).
[36]H. Thilakasiri, Qualitative Interpretation of LoadSettlement Curves of Bored Piles, Engineer: Journal of the Institution of Engineers, Sri Lanka, 40(4) (2007).
نشریه مهندسی عمران امیرکبیر
دوره 52، شماره 4
تیر 1399
صفحه 919-934

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