ارزیابی رفتار سیستم شالوده‌های همجوار متکی بر ماسه‌های مقید شده با مسلح کننده ژئوسل: مطالعه آزمایشگاهی

نوع مقاله : مقاله پژوهشی

نویسنده

گروه عمران، واحد شهرکرد، دانشگاه آزاد اسالمی، شهرکرد، ایران

چکیده

     تجربیات گذشته نشان می‌دهد که استفاده از مسلح کننده‌های سلولی در ماسه‌های ضعیف تاثیر قابل ملاحظه‌ای در فشار باربری و نشست شالوده‌های واقع بر این نوع بسترها دارد. با افزایش شدت بارها و ارتفاع سازه‌های در نزدیکی یکدیگر، ابعاد شالوده‌ها افزایش یافته و فاصله میان آن‌ها نزدیک‌تر می‌شود. قرار گرفتن شالوده‌ها در مجاورت یکدیگر سبب ایجاد اثر متقابل آن‌ها بر یکدیگر و در نتیجه تغییر مکانیسم گسیختگی، قابلیت باربری و نشست‌پذیری آن‌ها می‌گردد. رفتار شالوده‌های همسایه واقع بر خاک‌های ماسه‌ای مسلح شده با مسلح کننده‌های دو بعدی در ادبیات تخصصی همواره مطالعه شده است ولی این شرایط برای مسلح کننده‌های سلولی کمتر مورد توجه بوده است. از این جهت، در این مطالعه تاثیر همجواری دو شالوده‌ دایروی متقارن واقع بر ماسه نیمه متراکم تسلیح شده با ژئوسل مورد ارزیابی قرار گرفته است. با حفظ هندسه و موقعیت بهینه ثابت برای ژئوسل در خاک بستر، اثر تغییر فاصله بین شالوده‌ها بر میزان باربری و نشست آن‌ها مطالعه شده است. نتایج حاکی از آن است که وجود مسلح کننده سه بعدی در ترکیب با اثر همجواری شالوده‌ها می‌تواند باربری را بیش از 300% و نشست را تا بیش از 60% نسبت به یک شالوده منفرد مشابه واقع بر بستر غیرمسلح بهبود دهد. حداکثر باربری در حالتی به دست آمد که دو شالوده کاملا در مجاورت یکدیگر واقع شده باشند. زمانی که فاصله بین شالوده‌ها از سه برابر قطر شالوده بیشتر می‌شود اثر همجواری کاهش قابل توجهی داشته و هر کدام از شالوده‌ها تقریبا رفتاری مشابه یک شالوده منفرد را خواهند داشت.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Assessment Behavior of Cojointed Footings System Placed on Sands Encased by Geocell Reinforcement: Experimental Study

نویسنده [English]

  • Pezhman Fazeli Dehkordi
Department of Civil Engineering, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran
چکیده [English]

Previous experiences indicate that employing cellular reinforcements (such as geocell) in the weak sands beneath footings has significant influence on the bearing pressure and their settlement. The increased structures’ height and loads intensity lead to enhancement in the dimension of the footings and their spacing, thereby causing them to get closer to each other. Existing footings near each other create interaction problem that tends to change failure mechanism, the ability of load-carrying capacity and deformability. The behavior of nearby footings resting on sandy soils reinforced with 2D polymeric reinforcements has been elucidated in the literature; however, it has not been attended for cellular reinforcements. By keeping optimum geometry and location for cellular reinforcement embedded in the soil, the effect of spacing between footings on bearing capacity and settlement was studied. The results show that coupled effect of reinforcement and footing interference can enhance load carrying capacity by more than 300% and improve the settlement by more than 60% compared with single isolated footing on an unreinforced bed. Maximum bearing capacity is attained when two footings are beside. Spacing between footings more than three times of footing diameter represents substantial reduction in the interference effect and each footing almost acts as a single isolated footing.

کلیدواژه‌ها [English]

  • Weak sands
  • Footings interference effect
  • Cellular reinforcement
  • Bearing capacity and settlement
  • Failure mechanism
[1] A. Hegde, Geocell reinforced foundation beds-past findings, present trends and future prospects: A state-of-the-art review, Construction and Building Materials, 154 (2017) 658-674.
[2] D.I. Bush, C.G. Jenner, R.H. Bassett, The design and construction of geocell foundation mattresses supporting embankments over soft grounds, Geotextiles and Geomembranes, 9(1) (1990) 83-98.
[3] J.W. Cowland, S.C.K. Wong, Performance of a road embankment on soft clay supported on a Geocell mattress foundation, Geotextiles and Geomembranes, 12(8) (1993) 687-705.
[4] I. Al-Qadi, J. Hughes, Field evaluation of geocell use in flexible pavements, Transportation Research Record: Journal of the Transportation Research Board, (1709) (2000) 26-35.
[5] J. Han, S.K. Pokharel, X. Yang, C. Manandhar, D. Leshchinsky, I. Halahmi, R.L. Parsons, Performance of geocell-reinforced RAP bases over weak subgrade under full-Scale moving wheel loads, Journal of Materials in Civil Engineering, 23(11) (2011) 1525-1534.
[6] J. Guo, J. Han, S.D. Schrock, R.L. Parsons, Field evaluation of vegetation growth in geocell-reinforced unpaved shoulders, Geotextiles and Geomembranes, 43(5) (2015) 403-411.
[7] P. Fazeli Dehkordi, M. Ghazavi, N. Ganjian, Evaluation behavior of circular footings located on sand bed reinforced with geocell, Amir Kabir Journal of Civil Engineering, 53(5) (2021) doi: 10.22060/CEEJ.2020.17159.6479.
[8] P. Fazeli Dehkordi, U.F.A. Karim, Behaviour of circular footings confined by rigid base and geocell reinforcement, Arabian Journal of Geosciences, 13(20) (2020) 1100.
[9] P. Fazeli Dehkordi, M. Ghazavi, U.F.A. Karim, Bearing capacity-relative density behavior of circular footings resting on geocell-reinforced sand, European Journal of Environmental and Civil Engineering,  (2021) https://doi.org/10.1080/19648189.2021.1884901.
[10] J.G. Stuart, Interference between foundations, with special Reference to surface footings in sand, Géotechnique, 12(1) (1962) 15-22.
[11] V. Srinivasan, P. Ghosh, Experimental investigation on interaction problem of two nearby circular footings on layered cohesionless soil, Geomechanics and Geoengineering, 8(2) (2013) 97-106.
[12] S. Saran, V.C. Agarwal, Interference of surface footings in sand, Indian Geotechnical Journal, 4(2) (1974) 129-139.
[13] P. Ghosh, P.K. Basudhar, V. Srinivasan, K. Kunal, Experimental studies on interference of two angular footings resting on surface of two-layer cohesionless soil deposit, International Journal of Geotechnical Engineering, 9(4) (2015) 422-433.
[14] P. Fazeli Dehkordi, U.F.A. Karim, M. Ghazavi, N. Ganjian, Stochastic analysis of the capacity of two parallel footings on a thin sand layer, Proceedings of the Institution of Civil Engineers-Geotechnical Engineering, 172(4) (2019) 355-364.
[15] A.A. Lavasan, M. Ghazavi, A.V. Blumenthal, T. Schanz, Bearing capacity of interfering strip footings, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 144(3) (2018) 04018003.
[16] S. Saha Roy, K. Deb, Interference effect of closely spaced footings resting on granular fill over soft clay, International Journal of Geomechanics, ASCE, 19(1) (2019) 04018181.
[17] M. Ghazavi, P. Fazeli Dehkordi, Interference influence on behavior of shallow footings constructed on soils, past studies to future forecast: A state-of-the-art review, Transportation Geotechnics, 27 (2021) 100502.
[18] K.H. Khing, B.M. Das, S.C. Yen, V.K. Puri, E.E. Cook, Interference effect of two closely-spaced shallow strip foundations on geogrid-reinforced sand, Geotechnical and Geological Engineering, 10(4) (1992) 257-271.
[19] P. Ghosh, Interference effect of two nearby strip footings on reinforced sand, Contemporary Engineering Sciences, 2(12) (2009) 577-592.
[20] M. Al-Ashou, R. Sulaiman, J. Mandal, Effect of number of reinforcing layers on the interference between footings on reinforced sand, Indian Geotechnical Journal, 24(3) (1994) 285-301.
[21] A.M. Eltohamy, A.F. Zidan, Performance of interfering strip footings resting on reinforced sand under uniform and non-uniform load-experimental and numerical study, Journal of American Science, 9(1) (2013) 421-430.
[22] R. Noorzad, E. Manavirad, Bearing capacity of two close strip footings on soft clay reinforced with geotextile, Arabian Journal of Geosciences, 7(2) (2014) 623-639.
[23] A.G. Ekbote, L. Nainegali, Interference of two closely spaced footings embedded in unreinforced and reinforced soil medium: a finite element approach using ABAQUS, Arabian Journal of Geosciences, 12(22) (2019) 683.
[24] N. Biswas, P. Ghosh, Interaction of adjacent strip footings on reinforced soil using upper-bound limit analysis, Geosynthetics International, 25(6) (2018) 599-611.
[25] A. Kumar, S. Saran, Closely spaced footings on geogrid-reinforced sand, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 129(7) (2003) 660-664.
[26] A.A. Lavasan, M. Ghazavi, Behavior of closely spaced square and circular footings on reinforced sand, Soils and Foundations, 52(1) (2012) 160-167.
[27] E. Naderi, N. Hataf, Model testing and numerical investigation of interference effect of closely spaced ring and circular footings on reinforced sand, Geotextiles and Geomembranes, 42(3) (2014) 191-200.
[28] A.A. Lavasan, M. Ghazavi, T. Schanz, Analysis of interfering circular footings on reinforced soil by physical and numerical approaches considering strain-dependent stiffness, International Journal of Geomechanics, ASCE, 17(11) (2017) 04017096.
[29] S. Saha Roy, K. Deb, Closely spaced rectangular footings on sand over soft clay with geogrid at the interface, Geosynthetics International, 25(4) (2018) 412-426.
[30] S. Saha Roy, K. Deb, Effect of aspect ratio of footing on behavior of two closely-spaced footings on geogrid-reinforced sand, Geotextiles and Geomembranes,  48(4) (2020) 443-453.
[31] B. Paikaray, S.K. Das, B.G. Mohapatra, Effect of reinforcement layout on interference effect of square footings on reinforced crusher dust, International Journal of Geotechnical Engineering,  (2020) https://doi.org/10.1080/19386362.2020.1712531.
[32] A. Gupta, G.K. Lakshman, T. Sitharam, Interference of square footings on geocell reinforced clay bed: experimental and numerical studies. Proceedings of the 3rd World Congress on Civil, Structural, and Environmental Engineering (CSEE’18), Budapest, Hungary, ICGRE 142 (2018) 1-8.
[33] P. Fazeli Dehkordi, M. Ghazavi, N. Ganjian, U.F.A. Karim, Effect of geocell-reinforced sand base on bearing capacity of twin circular footings, Geosynthetics International, 26(3) (2019) 224-236.
[34] ASTM D2487, Standard practice for classification of soils for engineering purposes (Unified Soil Classification System), ASTM International, West Conshohocken, PA, USA, (2011).
[35] ASTM D7181, Method for consolidated drained triaxial compression test for soils, ASTM International, West Conshohocken, PA, USA, (2011).
[36] ASTM D4253, Standard test methods for maximum index density and unit weight of soils a vibratory table, ASTM International, West Conshohocken, PA, USA,  (2016).
[37] ASTM D4254, Standard test methods for minimum index density and unit weight of soils and calculation of relative density, (2016).
[38] ASTM D4885, Standard test method for determining performance strength of geomembranes by wide strip tensile method, ASTM International, West Conshohocken, PA, USA., (2011).
[39] K. Ueno, K. Miura, Y. Maeda, Prediction of ultimate bearing capacity of surface footings with regard to size effects, Soils and Foundations, 38(3) (1998) 165-178.
[40] Itasca, Fast Lagrangian Analysis of Continua (FLAC3D 5.00), Itasca Consulting Group Inc, Minneapolis, USA.,  (2015).
[41] P.D. Coduto, M.R. Yeung, A.W. Kitch, Geotechnical engineering: principles and practices, New Jersy: PHI publication,  (1999).
[42] K. Rajagopal, N.R. Krishnaswamy, G. Madhavi Latha, Behaviour of sand confined with single and multiple geocells, Geotextiles and Geomembranes, 17(3) (1999) 171-184.
[43] E. Buckingham, On physically similar systems; illustrations of the use of dimensional equations, Physical review, 4(4) (1914) 345-376.
[44] A. Hegde, T.G. Sitharam, Experimental and numerical studies on protection of buried pipelines and underground utilities using geocells, Geotextiles and Geomembranes, 43(5) (2015) 372-381.
[45] A. Hegde, T.G. Sitharam, Experiment and 3D-numerical studies on soft clay bed reinforced with different types of cellular confinement systems, Transportation Geotechnics, 10 (2017) 73-84.
[46] A. Hegde, T.G. Sitharam, Use of bamboo in soft-ground engineering and its performance comparison with geosynthetics: experimental studies, Journal of Materials in Civil Engineering, ASCE, 27(9) (2015) 04014256.
[47] S.K. Dash, Influence of relative density of soil on performance of geocell-reinforced sand foundations, Journal of Materials in Civil Engineering, ASCE, 22(5) (2010) 533-538.
[48] S.K. Dash, N.R. Krishnaswamy, K. Rajagopal, Bearing capacity of strip footings supported on geocell-reinforced sand, Geotextiles and Geomembranes, 19(4) (2001) 235-256.
[49] S. Amar, F. Canepa, Y. Frank, Experimental study of the settlement of shallow foundations. Vertical and Horizontal Deformations of Foundations and Embankments, ASCE, 40(2) (1994) 1602-1610.
[50] A. Hegde, T.G. Sitharam, 3-Dimensional numerical modelling of geocell reinforced sand beds, Geotextiles and Geomembranes, 43(2) (2015) 171-181.
[51] M. Ghazavi, A.A. Lavasan, Interference effect of shallow foundations constructed on sand reinforced with geosynthetics, Geotextiles and Geomembranes, 26(5) (2008) 404-415.
[52] M.T. Adams, J.G. Collin, Large model spread footing load tests on geosynthetic reinforced soil foundations, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 123(1) (1997) 66-72.
[53] J.L. Langhaar, Dimensional analysis and theory of models, John Wiley & Sons, New York, NY (1951).
[54] S. Sireesh, T.G. Sitharam, S.K. Dash, Bearing capacity of circular footing on geocell-sand mattress overlying clay bed with void, Geotextiles and Geomembranes, 27(2) (2009) 89-98.