نشست پی‌های نواری واقع بر خاک ماسه‌ای تحت اثر بارگذاری سیکلی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی عمران، واحد سمنان، دانشگاه آزاد اسلامی، سمنان، ایران

2 دانشکده مهندسی عمران و محیط زیست، دانشگاه صنعتی امیرکبیر، تهران، ایران

3 دانشکده مهندسی، دانشگاه فردوسی مشهد، مشهد، ایران

چکیده

موارد بسیاری وجود دارد که پی سازه­ علاوه بر بار استاتیکی، در معرض بارگذاری سیکلی قرار می­ گیرد که از آن جمله می ­توان به زلزله، بار ناشی از ترافیک و ارتعاش ناشی از ماشین­ آلات اشاره نمود. در این مطالعه آزمایشگاهی، تأثیر عرض پی، تراکم خاک ماسه ­ای، تعداد سیکل بارگذاری، شدت سربارهای استاتیکی و سیکلی بر نشست سیکلی پی نواری مورد بررسی قرار گرفته است. مصالح خاکی مورد استفاده در این تحقیق، ماسه متوسط بد دانه­ بندی شده (SP) است. مدل پی دارای عرض 5، 7/5 و 10 سانتی­ متر و طول آن، 34 سانتی ­متر است. سیستم بارگذاری به‌ صورت هوای فشرده است که قابلیت اعمال بار یکنواخت و سیکلی را دارا است. در خاک ماسه ­ای با تراکم متوسط و متراکم، مقدار متوسط نشست پی در سیکل اول بارگذاری، به ترتیب حدود 46 و 51 درصد کل نشست سیکلی است. خاک ماسه‌ای با تراکم متوسط زیر پی، در نشستی معادل 22 تا 27 درصد عرض پی دچار گسیختگی شده است. خاک ماسه‌ای متراکم زیر پی، در نشستی معادل 33 تا 43 درصد عرض پی دچار گسیختگی شده است. هر چه سربار کل وارد به خاک کمتر باشد، خاک تعداد سیکل بارگذاری بیشتری را تحمل می­ کند تا دچار گسیختگی شود؛ یعنی با ازدیاد سربار استاتیکی و سیکلی، خاک در تعداد سیکل کمتری دچار گسیختگی شده است. با توجه به ایجاد نشست ماندگار در پی تحت اثر بارهای سیکلی، در طراحی پی‌ها تحت اثر این نوع بار، مقدار نشست پیش‌بینی ‌شده حتماً بایستی از مقدار مجاز آن کمتر باشد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Settlement of Strip Footings on Sand Subjected to Cyclic Loading

نویسندگان [English]

  • Mahmoud Nikkhah 1
  • Seyed Majdeddin Mir Mohammad Hosseini 2
  • Saeed Abrishami 3
1 Department of Civil Engineering, Semnan Branch, Islamic Azad University, Semnan, Iran
2 Department of Civil and Environmental Engineering, Amirkabir University, Tehran, Iran
3 Department of Civil Engineering, Ferdousi University, Mashhad, Iran
چکیده [English]

There are many cases in which the foundation, in addition to static load, is exposed to cyclic loading, such as earthquakes, traffic loads, and machine vibrations. In this laboratory study, the effect of foundation width, sandy soil density, number of loading cycles, static and cyclic overhead intensity on cyclic strip foundation settlement has been investigated. The soil material used in this research is poorly graded medium sand (SP). The foundation model has a width of 5, 7.5 and 10 cm and its length is 34 cm. In medium and dense sandy soils, the average amount of foundation settlement in the first loading cycle is about 46 and 51% of the total cyclic settlement, respectively. Medium-density sandy soils below the foundation have failed at a settlement of 22 to 27% of the foundation width. The dense sandy soil beneath the foundation has failed at a settlement of 33 to 43% of the width of the foundation. The lower the total overhead entering the soil, the more loading cycles the soil can withstand to fail; That is, with increasing static and cyclic overhead, the soil is failed in a smaller number of cycles. Due to the creation of permanent settlements under the effect of cyclic loads, in the design of foundations under the effect of this type of load, the amount of predicted settlement must be less than the allowable amount.

کلیدواژه‌ها [English]

  • Sand density
  • foundation width
  • settlement
  • static overhead
  • cyclic overhead

مراجع

[1] G.P. Raymond, F.E. Komos, Repeated load testing of a model plane strain footing, Canadian Geotechnical Journal, 15(2) (1978) 190-201.
[2] R.J. Fragaszy, E. Lawton, Bearing capacity of reinforced sand subgrades, Journal of Geotechnical Engineering, 110(10) (1984) 1500-1507.
[3] K. Khing, B. Das, V. Puri, E. Cook, S. Yen, The bearing-capacity of a strip foundation on geogrid-reinforced sand, Geotextiles and Geomembranes, 12(4) (1993) 351-361.
[4] V. Puri, S. Yen, B. Das, B. Yeo, Cyclic load-induced settlement of a square foundation on geogrid-reinforced sand, Geotextiles and Geomembranes, 12(6) (1993) 587-597.
[5] B. Shin, S. Kim, B. Yeo, B. Das, H. Imamoto, Permanent settlement of a square shallow foundation sand due to cyclic load, in:  Earthquake Geotechnical Engineering, 1995, pp. 779-783.
[6] B. Das, E. Shin, Strip foundation on geogrid-reinforced clay: behavior under cyclic loading, Geotextiles and Geomembranes, 13(10) (1994) 657-667.
[7] S. Abrishami, S. Mir Mohammad Hosseini, Design and development of a new physical model of strip footings on reinforced soil media under cyclic loadings, Amirkabir Journal of Civil Engineering, 41(2) (2010) 73-83. (in Persian)
[8] S.K. Dash, N. Krishnaswamy, K. Rajagopal, Bearing capacity of strip footings supported on geocell-reinforced sand, Geotextiles and Geomembranes, 19(4) (2001) 235-256.
[9] M. Mosallanezhad, N. Hataf, A. Ghahramani, Experimental study of bearing capacity of granular soils, reinforced with innovative grid-anchor system, Geotechnical and Geological Engineering, 26(3) (2008) 299-312.
[10] S. Sireesh, T. 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.
[11] M.H. Mohamed, Two dimensional experimental study for the behaviour of surface footings on unreinforced and reinforced sand beds overlying soft pockets, Geotextiles and Geomembranes, 28(6) (2010) 589-596.
[12] M. El Sawwaf, A.K. Nazir, Behavior of repeatedly loaded rectangular footings resting on reinforced sand, Alexandria Engineering Journal, 49(4) (2010) 349-356.
[13] S.M. Tafreshi, A. Dawson, Behaviour of footings on reinforced sand subjected to repeated loading–Comparing use of 3D and planar geotextile, Geotextiles and Geomembranes, 28(5) (2010) 434-447.
[14] N. Hataf, A. Boushehrian, A. Ghahramani, Experimental and numerical behavior of shallow foundations on sand reinforced with geogrid and grid anchor under cyclic loading,  (2010).
[15] S. Abrishami, The Study of Cyclic Bearing Capacity of Dry Geogrid Reinforced Sand by Physical Modeling, Amirkabir University of Technology, Tehran, Iran,  (2010). (in Persian)
[16] S. Mir Mohammad Hosseini, S. Abrishami, t‌h‌e i‌n‌f‌l‌u‌e‌n‌c‌e o‌f l‌o‌a‌d‌i‌n‌g r‌a‌t‌e o‌n t‌h‌e b‌e‌a‌r‌i‌n‌g c‌a‌p‌a‌c‌i‌t‌y o‌f s‌t‌r‌i‌p f‌o‌o‌t‌i‌n‌g‌s r‌e‌s‌t‌i‌n‌g o‌n g‌e‌o‌g‌r‌i‌d r‌e‌i‌n‌f‌o‌r‌c‌e‌d s‌a‌n‌d, Sharif Journal of Civil Engineering, (1) (2012) 39-47. (in Persian)
[17] S.M. Tafreshi, A. Dawson, A comparison of static and cyclic loading responses of foundations on geocell-reinforced sand, Geotextiles and Geomembranes, 32 (2012) 55-68.
[18] M. Abu-Farsakh, Q. Chen, R. Sharma, An experimental evaluation of the behavior of footings on geosynthetic-reinforced sand, Soils and Foundations, 53(2) (2013) 335-348.
[19] B. Hotti, P. Rakaraddi, S. Kodde, Behavior of square footing resting on reinforced sand subjected to incremental loading and unloading, International Journal of Research in Engineering and Technology, 3(6) (2014).
[20] P. S‌h‌a‌r‌i‌f‌i, S. M‌o‌g‌h‌a‌d‌d‌a‌s T‌a‌f‌r‌e‌s‌h‌i, E‌x‌p‌e‌r‌i‌m‌e‌n‌t‌a‌l s‌t‌u‌d‌y o‌f l‌a‌y‌e‌r‌e‌d g‌e‌o‌c‌e‌l‌l r‌e‌i‌n‌f‌o‌r‌c‌e‌d b‌e‌d s‌u‌b‌j‌e‌c‌t‌e‌d t‌o r‌e‌p‌e‌a‌t‌e‌d l‌o‌a‌d, Sharif Journal of Civil Engineering, (4.1) (2014) 75-83. (in Persian)
[21] E. Badakhshan, A. Noorzad, Effect of footing shape and load eccentricity on behavior of geosynthetic reinforced sand bed, Geotextiles and Geomembranes, 45(2) (2017) 58-67.
[22] A. Boushehrian, N. Hataf, A. Ghahramani, Modeling of the cyclic behavior of shallow foundations resting on geomesh and grid-anchor reinforced sand, Geotextiles and Geomembranes, 29(3) (2011) 242-248.
[23] A. Tabaroei, S. Abrishami, E. Seyedi Hosseininia, N. Ganjian, A study on bearing capacity of circular footing resting on geogrid reinforced granular soil, Amirkabir Journal of Civil Engineering, 50(5) (2018) 973-986. (in Persian)
[24] A. Tabaroei, S. Abrishami, H.E. Seyedi, N. Ganjian, An Experimental Investigation on the Effect of Loading Frequency on the Settlement and Bearing Capacity of the Footing over the Soil Reinforced by One Geogrid Layer,  (2018). (in Persian)
[25] M.Y. Fattah, H.H. Karim, H.H. Al-Qazzaz, Effect of Embedment Depth on Cyclic Behavior of Tank Footings on Dry Sand, Transportation Infrastructure Geotechnology, 9(2) (2022) 220-235.
[26] C. Jayalath, C. Gallage, K. Wimalasena, J. Lee, J. Ramanujam, Performance of composite geogrid reinforced unpaved pavements under cyclic loading, Construction and Building Materials, 304 (2021) 124570.
[27] M.N.A. Raja, S.K. Shukla, Experimental study on repeatedly loaded foundation soil strengthened by wraparound geosynthetic reinforcement technique, Journal of Rock Mechanics and Geotechnical Engineering, 13(4) (2021) 899-911.
[28] G.M. Latha, A. Somwanshi, Bearing capacity of square footings on geosynthetic reinforced sand, Geotextiles and Geomembranes, 27(4) (2009) 281-294.
[29] M. Kargar, S.M. Mir Mohammad Hosseini, Influence of reinforcement stiffness and strength on load-settlement response of geocell-reinforced sand bases, European Journal of Environmental and Civil Engineering, 22(5) (2018) 596-613.
نشریه مهندسی عمران امیرکبیر
دوره 55، شماره 1
فروردین 1402
صفحه 109-130

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