مدل سازی فیزیکی ارزیابی ظرفیت باربری شیروانی ماسه ای بهسازی شده با لبه

نوع مقاله : پژوهشی اصیل (کامل)

نویسندگان
احسان سعیدی 1
آرش رزم خواه 2
محسن کمالیان 3
فرج اله عسکری 3
1 دانشجوی دکتری گروه مهندسی ژئوتکنیک، دانشکده فنی، واحد تهران جنوب، دانشگاه آزاد اسلامی، تهران، ایران
2 استادیار گروه مهندسی ژئوتکنیک، دانشکده فنی، واحد تهران جنوب، دانشگاه آزاد اسلامی، تهران، ایران
3 استاد پژوهشکده مهندسی ژئوتکنیک، پژوهشگاه بین المللی زلزله شناسی و مهندسی زلزله
10.22034/24.1.83
چکیده
امروزه قرارگرفتن پی در کنار شیروانی­های خاکی همانند استقرار پی در نزدیکی گودبرداری­ها، دیواره­های نگهــــبان یا پی پـل­ها و دکل­های انتقال برق امری اجتناب ناپذیر است. در زمان قرارگیری پی در کنار شیروانی خاکی، ظرفیت باربری نهایی آن بسته به فاصله استقرار از تاج شیروانی به مقدار قابل توجهی کاهش می­یابد. از این رو بهبود ظرفیت باربری و تثبیت شیروانی خاکی یکی از مهمترین چالش­ها به شمار می­آید. استفاده از لبه به عنوان محصورکننده پیوسته یک راه حل مناسب برای این موضوع می­باشد. پی لبه­دار ترکیبی از پی سطحی با لبه­های داخلی یا جانبی از جنس فولاد یا بتن مسلح می­باشد که با ایجاد شرایط محصورکنندگی در خاک زیر پی، تشکیل گـوه­ی گسیختگی را به تراز نوک لبه انتقال می­دهد. در این تحقیق، مدل فیزیکی پی نواری بهسازی شده با یک طرف لبه در مجاورت شیروانی ماسه­ای، تحت بارگذاری قائم مورد ارزیابی قرار گرفت. تاثیر پارامتر­های عمق لبه (Hs) و فاصله قرارگیری پی از تاج شیروانی (b) بر ظرفیت باربری و نشست بررسی شد. ارزیابی نتایج نشان داد که، استفاده از لبه موجب بهبود ظرفیت باربری و مقدار نشست می­گردد. با افزایش عمق لبه (Hs=1, 2, 3, 4B)، بسته به محل قرارگیری پی نسبت به تاج شیروانی، ظرفیت باربری در محدود 104 تا 232 درصد نسبت به حالت بهسازی نشده افزایش می­یابد. به منظور ارزیابی اثر فاصله قرارگیری پی از تاج شیروانی، سه فاصله 0، 1 و 2 برابر عرض پی به عنوان پارامتر متغیر در نظر گرفته شد. نتایج نشان داد که، افزایش فاصله قرارگیری پی از تاج شیروانی موجب افزایش ظرفیت باربری در حالت بدون بهسازی می­گردد. استفاده از لبه در پی مستقر بر تاج شیروانی ماسه­ای بیشترین تاثیر بر ظرفیت باربری را داشته و با افزایش فاصله قرارگیری پی نسبت به تاج شیروانی تاثیر استفاده از لبه کاهش می­یابد. همچنین استفاده از لبه به عنوان بهسازی موجب کاهش نشست می­گردد. فاکتور کاهش نشست بسته به افزایش عمق لبه و کاهش فاصله قرارگیری پی از تاج شیروانی در محدوده 4 تا 72 درصد کاهش می­یابد. علاوه بر این، تاثیر استفاده از لبه بر نشست نامتقارن و مکانیسم گسیختگی آن مورد ارزیابی قرار گرفت. نتایج به خوبی نشان داد که، پی مستقر در مجاورت شیروانی ماسه­ای دارای نشست نامتقارن و در جهت عقربه­های ساعت بوده که با استفاده از لبه جهت نشست نامتقارن تغییر می­یابد. در زمان قرارگیری پی در مجاورت شیروانی و در نشست 15 درصدی عرض پی با افزایش طول لبه (Hs=1B, 3B) مقدار کج شدگی نامتقارن پی به ترتیب 46 تا 24 درصد کاهــش می­یابد. همچنین، استفاده از لبه موجب تغییر مکانیسم گسیختگی گشته و بسته به ارتفاع لبه و فاصله پی از تاج شیروانی مکانیسم گسیختگی از حالت گسیختگی سطحی و کم عمق به گسیختگی دامنه و پای شیروانی تغییر می­یابد.

کلیدواژه‌ها

موضوعات

عنوان مقاله English

Bearing Capacity Evaluation of Skirted Reinforced Sand Slopes by Physical Modeling

نویسندگان English

ehsan saeedi 1
Arash Razmkhah 2
mohsen kamalian 3
Faradjollah Askari 3
1 Department of Civil Engineering, Faculty of Engineering, South Tehran Branch, Islamic Azad University, Ahang Bld., Abouzar Bld., Basij Highway, Tehran, Iran.
2 Department of Civil Engineering, Faculty of Engineering, South Tehran Branch, Islamic Azad University, Ahang Bld., Abouzar Bld., Basij Highway, Tehran, Iran, (Corresponding author),
3 Geotechnical Engineering Research Centre, International Institute of Earthquake Engineering and Seismology (IIEES), No. 21, Arghavan Street, North Dibajee, Farmanieh, Tehran, Iran
چکیده English

Foundations are sometimes located either on a sloped surface or near the crown of a slope. Obvious examples can be seen in the footings of bridges abutments, foundations near excavations, retaining walls, and electric transmission towers built on mountain slopes. When the footing is placed near the edge of sloping ground, the bearing capacity may be significantly reduced, depending on the location of the footing concerning the slope. Therefore, the bearing capacity and stability of a slope is one of the most important research issues in geotechnical engineering. The adjacent soil's bearing capacity and the slope's stability can be increased by installing continuous confining structures like skirts. Skirted foundations are a type of shallow foundation with internal or lateral skirts made of steel or reinforced concrete. Using a skirt due to confinement of the soil beneath the foundation and transmitting the shear Failure at the level of the skirt tip. In this research, a series of laboratory tests were conducted on strip footing models adjacent to sand slope whit one side vertical skirt to evaluate the load-settlement response subjected to vertical compression loading. The effects of skirt depth (Hs) and setback distance (b) of the model on the bearing capacity and settlement of skirted foundations were studied. The results of the model tests have shown that using skirts improves the bearing capacity and settlement values of skirted foundations compared with shallow foundations without a skirt. The ultimate bearing capacity of skirted foundations increases up to about 104 to 232% with increasing the ratio of skirt depth to foundation width. To investigate the effect of setback distance on the skirted foundation behavior, three different distances of footing from crest to the width of the footing of 0, 1, and 2 were used. The results showed that the increase in the ratio of the distance of footing from the crest to the width of footing caused to increase in the ultimate bearing capacity of only footing. The results showed when the skirted footing is placed directly at the crest (b=0), increasing the depth of skirts leads to a significant increase in the bearing capacity. By increasing the edge distance from the slope crest to the footing, the effect of utilized skirts decreases. The Settlement Reduction Factor (SRF) decreased from 4 to 72% with the increase in the depth of the skirt and with a decrease in setback distance. Furthermore, the effect of a single-side skirt strip foundation resting on the top of the sand slope was investigated on the values of foundation tilting and failure mechanism. Evaluating results showed that strip footing near the slope has a clockwise tilt angle and after using one single skirt the tilt angle got changed. It was observed that in setback distance b/B=0 under s/B=15% with an increase in skirt depth (Hs=1b, 3B), the reduction values of footing tilt were from 46 to 24%, respectively. In the end, utilized skirts affect the failure mechanism and dependent on skirt length and setback distance change the failure pattern of the soil, face failure to toe, or base failure.

کلیدواژه‌ها English

sandy slope
Skirted foundation
Physical Modeling
bearing capacity
Settlement
Failure mechanism
1. Hu, Y., Randolph, M. F., & Watson, P. G. (1999). Bearing response of skirted foundation on nonhomogeneous soil. Journal of Geotechnical and Geoenvironmental Engineering, 125(11), 924-935.
2. Zhu, F. (1999). Centrifuge modelling and numerical analysis of bearing capacity of ring foundations on sand. PhD thesis, Memorial University of Newfoundland, St. John’s, Canada.
3. Eid, H. T. (2013). Bearing capacity and settlement of skirted shallow foundations on sand. International Journal of Geomechanics, 13(5), 645-652.
4. Eid HT, Alansari OA, Odeh AM, Nasr MN and Sadek HA (2009) A comparative study on the behavior of square foundations resting on confined sand. Canadian Geotechnical Journal 46(4): 438–453.
5. Fiumana, N., Bienen, B., Govoni, L., Gourvenec, S., Cassidy, M. J., & Gottardi, G. (2019). Combined loading capacity of skirted circular foundations in loose sand. Ocean Engineering, 183, 57-72. ‌
6. Al-Aghbari, M. Y., & Khan, A. J. (2002). BEHAVIOUR OF SHALLOW STRIP FOUNDATIONS WITH STRUCTURAL SKIRTS RESTING ON DENSE SAND. In Challenges of Concrete Construction: Volume 6, Concrete for Extreme Conditions: Proceedings of the International Conference held at the University of Dundee, Scotland, UK on 9–11 September 2002 (pp. 737-746). Thomas Telford Publishing.
7. Al-Aghbari, M. Y., & Mohamedzein, Y. E. (2004). Bearing capacity of strip foundations with structural skirts. Geotechnical and Geological Engineering, 22(1), 43-57.
8. Al-Aghbari, M. Y., & Mohamedzein, Y. A. (2006). Improving the performance of circular foundations using structural skirts. Proceedings of the Institution of Civil Engineers-Ground Improvement, 10(3), 125-132. ‌
9. Al-Aghbari, M. Y. (2007). Settlement of shallow circular foundations with structural skirts resting on sand. J Eng Res, 4(1), 11-16.
10. Al-Aghbari, M. Y., & Dutta, R. K. (2008). Performance of square footing with structural skirt resting on sand. Geomechanics and Geoengineering: An International Journal, 3(4), 271-277.
‌
11. El Wakil, A. Z. (2010). Horizontal capacity of skirted circular shallow footings on sand. Alexandria Engineering Journal, 49(4), 379-385.
12. El Wakil, A. Z. (2013). Bearing capacity of skirt circular footing on sand. Alexandria Engineering Journal, 52(3), 359-364.
13. Nazir, A. K., & Azzam, W. R. (2010). Improving the bearing capacity of footing on soft clay with sand pile with/without skirts. Alexandria Engineering Journal, 49(4), 371-377.
‌
14. Momeni, E., Nazir, R., Armaghani, D. J., & Sohaie, H. (2015). Bearing capacity of precast thin-walled foundation in sand. Proceedings of the Institution of Civil Engineers-Geotechnical Engineering, 168(6), 539-550.
‌
15. Villalobos FAJ (2007) Bearing capacity of skirted foundations in sand. VI Congreso Chileno de Geotecnia SOCHIGE. Ponti Ficia Catholic University, Valdivia, Chile.
16. Punrattanasin, P. (2009). The horizontal capacity of circular and square sheet pile skirted foundations at various sand densities. International Journal of Geotechnical Engineering, 3(4), 499-507. ‌
17. Gholipour, S., & Makarchian, M. (2018). Study of the behaviour of skirted shallow foundations resting on sand. International Journal of Physical Modelling in Geotechnics, 18(3), 117-130.
‌
18. Mahmood, M. R., Fattah, M. Y., & Khalaf, A. (2020). Experimental investigation on the bearing capacity of skirted foundations on submerged gypseous soil.
19. Al-Aghbari, M. Y., & Mohamedzein, Y. E. A. (2020). The use of skirts to improve the performance of a footing in sand. International Journal of Geotechnical engineering, 14(2), 134-141. ‌
20. Watson, P. G., & Randolph, M. F. (1998). SKIRTED FOUNDATIONS IN CALCAREOUS SOIL. Proceedings of the Institution of Civil Engineers-Geotechnical Engineering, 131(3), 171-179.
‌
21. Byrne, B.W. (2000). Investigations of suction caissons in dense sand. PhD thesis. Oxford University, Oxford, UK.
22. Byrne, B. W., Villalobos, F., Houlsby, G. T., & Martin, C. M. (2003). Laboratory testing of shallow skirted foundations in sand. In BGA International Conference on Foundations: Innovations, observations, design and practice: Proceedings of the international conference organized by British Geotechnical Association and held in Dundee, Scotland on 2–5th September 2003 (pp. 161-173). Thomas Telford Publishing.
‌
23. Yun, G. J., & Bransby, M. F. (2003). Centrifuge modeling of the horizontal capacity of skirted foundations on drained loose sand. In BGA International Conference on Foundations: Innovations, observations, design and practice: Proceedings of the international conference organised by British Geotechnical Association and held in Dundee, Scotland on 2–5th September 2003 (pp. 975-984). Thomas Telford Publishing.
‌
24. Mana DSK, Gourvenec SM, Randolph MF and Hossain MS (2012) Failure mechanisms of skirted foundations in uplift and compression. International Journal of Physical Modelling in Geotechnics 12(2):47–62.
25. Acosta-Martinez, H. E., Gourvenec, S., & Randolph, M. F. (2012). Centrifuge study of capacity of a skirted foundation under eccentric transient and sustained uplift. Géotechnique, 62(4), 317-328. ‌
26. Bransby, M. F., & Randolph, M. F. (1997, January). Finite element modelling of skirted strip footings subject to combined loadings. In The Seventh International Offshore and Polar Engineering Conference. International Society of Offshore and Polar Engineers.
‌
27. Bransby, M. F., & Randolph, M. F. (1998, January). The effect of skirted foundation shape on response to combined V-MH loadings. In The Eighth International Offshore and Polar Engineering Conference. International Society of Offshore and Polar Engineers.
28. ‌Bransby, F., & Randolph, M. (1999). The effect of embedment depth on the undrained response of skirted foundations to combined loading. Soils and Foundations, 39(4), 19-33.
‌
29. Hu, Y., & Randolph, M. F. (1998, January). H-adaptive FE analysis of bearing capacity of skirted foundations. In The Eighth International Offshore and Polar Engineering Conference. International Society of Offshore and Polar Engineers.
‌
30. Bransby, M. F., & Yun, G. J. (2009). The undrained capacity of skirted strip foundations under combined loading. Géotechnique, 59(2), 115-125. ‌
31. Azzam, W. R., & Farouk, A. (2010). Experimental and numerical studies of sand slopes loaded with skirted strip footing. Electronic Journal of Geotechnical Engineering, 15, 795-812.
32. Azzam, W. R. (2015). Finite element analysis of skirted foundation adjacent to sand slope under earthquake loading. HBRC Journal, 11(2), 231-239. ‌
33. Pusadkar, S. S., & Dhaygude, P. S. PLAXIS 2D.
‌
34. Changizi, F., Razmkhah, A., Ghasemzadeh, H., & Amelsakhi, M. (2022). Behavior of geocell-reinforced soil abutment wall: A physical modeling. Journal of Materials in Civil Engineering, 34(3), 04021495.
35. Jahanian, M. S., Razmkhah, A., Ghasemzadeh, H., & Vosoughifar, H. (2022). Bearing capacity of the strip footing located on the sand reinforced by geocell under eccentric load. Arabian Journal of Geosciences, 15(15), 1-18.
36. Ghasemzadeh, H., and F. Akbari. (2019). Determining the bearing capacity factor due to nonlinear matric suction distribution in the soil. Can. J. Soil Sci. 99 (4): 434–446.
37. Ghasemzadeh, H., and F. Akbari. (2020). Investigation of soil active wedge angle with linear matric suction distribution below the footing. Int. J. Civ. Eng. 18 (2): 161–168.

38. Keskin, M. S., and M. Laman. (2013). Model Studies of Bearing Capacity of Strip Footing on Sand Slope. KSCE Journal of Civil Engineering. 17 (4): 699–711.
39. Mofidi Rouchi, J., Farzaneh, O., & Askari, F. (2014). Bearing capacity of strip footings near slopes using lower bound limit analysis. Civil Engineering Infrastructures Journal, 47(1), 89-109.
40. Shiraishi, S. (1990). Variation in Bearing Capacity Factors of Dense Sane Assessed by Model Loading Tests. Soils and Foundations, 30(1), 17-26.
41. Cerato AB and Lutengger AJ (2007) Scale effects of shallow foundation bearing capacity on granular material. Journal of Geotechnical and Geoenvironmental Engineering ASCE 133(10): 1192–1202.
42. Tatsuoka F, Okahara M, Tanaka T et al. (1991) Progressive failure and particle size effect in bearing capacity of a footing on sand. Geotechnical Special Publication 27(2): 788–802.
43. Yamaguchi H, Kimura T and Fujii N (1977). On the scale effect of footings in dense sand. Proceeding of the 9th International Conference on Soil Mechanics and Foundation Engineering, Japanese Society of Soil Mechanics and Foundation Engineering, Tokyo, Japan, vol. 1, pp. 795–798.
44. Kusakabe, O, Foundations, in: R.N. Taylor (Ed.), Geotech. Centifuge Technology, vol. 37, Blackie Academi & Professional, London, 1995, pp. 828–842, Cand. Geotechnical J (Chapter 6).
مهندسی عمران مدرس
دوره 24، شماره 1
فروردین و اردیبهشت 1403
صفحه 83-96