مقایسه رفتار دینامیکی نمونه‌ی خاک ماسه‌ای بازسازی ‌شده و مغزه‌گیری ‌شده توسط آزمایش ستون تشدید در خمش

نوع مقاله : مقاله پژوهشی

نویسندگان

1 بخش ژئوتکنیک و زیرساخت، مرکز تحقیقات راه، مسکن و شهرسازی، تهران، ایران

2 دانشکده ی مهندسی عمران، دانشگاه یزد، یزد، ایران

چکیده

تعیین خواص دینامیکی خاک‌ها مسئله‌ای مهم در حل مسائل مهندسی ژئوتکنیک لرزه‌ای به شمار می‌رود. در این راستا انواع متعددی از روش‌های صحرایی و آزمایشگاهی با مزیت‌ها و محدودیت‌های متفاوت با توجه به حل مسائل مختلف در دسترس هستند. یکی از معضلات پیش روی مهندسین اختلاف بین نتایج آزمایش‌های در محل و آزمایشگاهی است. از دلایل تفاوت بین مقادیر پارامترهای دینامیکی حاصل از آزمایش‌های در محل و آزمایشگاهی دست‌خوردگی نمونه‌ها، تفاوت شرایط تنش و از بین رفتن سیمانی شدن است که عدم توجه به این موارد بر خواص دینامیکی خاک‌ها می‌تواند موجب وقوع صدمات جدی در اثر تحلیل‌های غیرواقعی زمین شود. از میان روش‌های آزمایشگاهی، آزمایش ستون تشدید یکی از آزمایش‌های تعیین خواص دینامیکی‌ خاک‌ها در کرنش‌های کوچک به شمار می‌رود. در این پژوهش با انجام آزمایش ستون تشدید در خمش، مدول یانگ و نسبت میرایی مصالح خاکی دست نخورده و بازسازی ‌شده مورد ارزیابی قرار گرفته است. اثرات تنش محدود کننده و ناهمسانی تنش نیز در روند تغییرات مدول یانگ و نسبت میرایی بررسی شده است. نتایج بررسی‌ها کاهش مدول یانگ را بر اثر دست خوردگی نشان می‌دهد در حالی‌ که بر نسبت میرایی اثر قابل ‌ملاحظه‌ای نداشته است. افزایش تنش محدود کننده و ناهمسانی تنش افزایش مدول یانگ را به دنبال داشته است. مقایسه‌ی نتایج نسبت میرایی با دو روش زوال دامنه‌ی ارتعاش و نصف عرض توان بیشتر بودن مقادیر نسبت میرایی حاصل از روش نصف عرض توان را نشان می‌دهد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Comparison of Dynamic Behavior of Reconstituted and Core Barrel Sandy Soil Sample by Resonant Column Test in Flexural Mode

نویسندگان [English]

  • Ata Aghaei Araei 1
  • Somayeh Ahmadi 2
  • Hamid Mehrnahad 2
  • Nahid Attarchian 1
1 Associate professor, Geotechnical Engineering Department, Road, Housing & Urban Development Research Center, Tehran, Iran
2 Civil Engineering Faculty, Yazd Univercity, Yazd, Iran
چکیده [English]

Determining the dynamic properties of soils is an important issue in solving seismic geotechnical engineering problems. In this respect, several types of field and laboratory methods are available with different advantages and limitations regarding solving different problems. The difference between the results of in-site and laboratory tests is one of the engineers’ difficulties. Some reasons for the difference between the values ​​of dynamic parameters which achieved from field and laboratory tests, are the remolding effect of samples, difference in stress conditions and loss of cementation; negligence of these facts in soil dynamic properties may lead to serious damage due to unrealistic soil analysis. Among the laboratory methods, the resonant column test is one of the methods which determines the dynamic properties of soils at small strains. In this research, Young’s modulus and damping ratio of core barrel and reconstituted earth materials have been studied by performing resonant column test in flexural mode. The effects of confining pressure and anisotropic confining pressure was studied by using the Young’s modulus and damping ratio versus flexural strain diagrams. The results of the study indicate that reconstituting reduces the Young’s modulus, but the variation of damping ratio versus shear strain for core barrel and reconstituted samples is negligible. Increase in the confining pressure and anisotropic confining pressure result in the increase of Young’s modulus. Comparing the damping ratio results with the two methods of free vibration decay and half-power bandwidth indicates that the damping ratio values ​​obtained from the half-power bandwidth method are higher.

کلیدواژه‌ها [English]

  • Young’s modulus
  • Damping ratio
  • Flexural mode of resonant column
  • Core Barrel sample
  • Reconstituted sample
[1] S.L. Kramer, Geotechnical Earthquake Engineering, Prentice Hall, USA, 1996.
[2] M. Payan, K. Senetakis, A. Khoshghalb, N. Khalili, Effect of gradation and particle shape on small-strain Young’s modulus and Poisson’s ratio of sands, International Journal of Geomechanics, 17(5) (2017) 04016120.
[3] M. Payan, M. Khoshini, R. Jamshidi Chenari, Elastic Dynamic Young’s Modulus and Poisson’s Ratio of Sand–Silt Mixtures, Journal of Materials in Civil Engineering, 32(1) (2020) 04019314.
[4] F. Jafarzadeh, H. Sadeghi, Experimental study on dynamic properties of sand with emphasis on the degree of saturation, Soil Dynamics and Earthquake Engineering, 32(1) (2012) 26-41.
[5] Y. Chuancheng, C. Wenxia, D. Haiyue, Research on comparison of the maximum dynamic shear modulus test, Procedia Engineering, 28 (2012) 230-234.
[6] Y. Jafarian, A. Haddad, H. Javdanian, Estimating the shearing modulus of Boushehr calcareous sand using resonant column and cyclic triaxial experiments, Modares Civil Engineering journal, 15(4) (2015) 9-19, (in Persian).
[7] Y. Jafarian, H. Javdanian, A. Haddad, Comparing dynamic behavior of Hormuz calcareous and Babolsar siliceous sands under identical conditions, (2016), (in Persian).
[8] H. Patiño, E. Martínez, J. González, A. Soriano, Shear modulus of a saturated granular soil derived from resonant-column tests, Acta Geotechnica Slovenica, 14(2) (2017) 33-45.
[9] D. Park, T. Kishida, Shear modulus reduction and damping ratio curves for earth core materials of dams, Canadian Geotechnical Journal, 56(1) (2019) 14-22.
[10] S.K. Saxena, K.R. Reddy, Dynamic moduli and damping ratios for Monterey No. 0 sand by resonant column tests, Soils and Foundations, 29(2) (1989) 37-51.
[11] G. Cascante, C. Santamarina, N. Yassir, Flexural excitation in a standard torsional-resonant column device, Canadian Geotechnical Journal, 35(3) (1998) 478-490.
[12] X. Gu, J. Yang, M. Huang, Laboratory measurements of small strain properties of dry sands by bender element, Soils and Foundations, 53(5) (2013) 735-745.
[13] H. He, K. Senetakis, A study of wave velocities and Poisson ratio of recycled concrete aggregate, Soils and Foundations, 56(4) (2016) 593-607.
[14] M. Payan, K. Senetakis, A. Khoshghalb, N. Khalili, Influence of particle shape on small-strain damping ratio of dry sands, Géotechnique, 66(7) (2016) 610-616.
[15] A. Aghaei Araei, S. Ahmadi, H. Mehrnahad, N. Attarchian, I. Rahmani, A.S. Salamat, H. Hasani, Remolding effect on dynamic behavior of sandy soil samples using resonant column tests, Sharif Journal of Civil Engineering, (2020), (in Persian).
[16] H.Y. Fang, Foundation engineering handbook, Springer Science & Business Media, 2013.
[17] M. Hatanaka, Y. Suzuki, T. Kawasaki, M. Endo, Cyclic undrained shear properties of high quality undisturbed Tokyo gravel, Soils and Foundations, 28(4) (1988) 57-68.
[18] S. Goto, Y. Suzuki, S. NISHIO, H. OHOKA, Mechanical properties of undisturbed tone-river gravel obtained by in-situ freezing method, Soils and Foundations, 32(3) (1992) 15-25.
[19] B. Song, A. Tsinaris, A. Anastasiadis, K. Pitilakis, W. Chen, Small-strain stiffness and damping of Lanzhou loess, Soil Dynamics and Earthquake Engineering, 95 (2017) 96-105.
[20] Y. Jafarian, H. Javdanian, A. Haddad, Dynamic properties of calcareous and siliceous sands under isotropic and anisotropic stress conditions, Soils and foundations, 58(1) (2018) 172-184.
[21] Y. Jafarian, H. Javdanian, A. Haddad, Strain-dependent dynamic properties of Bushehr siliceous-carbonate sand: experimental and comparative study, Soil Dynamics and Earthquake Engineering, 107 (2018) 339-349.
[22] Y. Jafarian, H. Javdanian, A. Haddad, Laboratory study on the maximum shear modulus of Bushehr calcareous sand, Sharif Journal of Civil Engineering, 33(1.2) (2017) 45-52, (in Persian).
[23] M. Payan, Study of Small Strain Dynamic Properties of Sands and Silty Sands, university of New South Wales Sydney, Australia, 2017.
[24] K. Senetakis, M. Payan, Small strain damping ratio of sands and silty sands subjected to flexural and torsional resonant column excitation, Soil Dynamics and Earthquake Engineering, 114 (2018) 448-459.
[25] K. Senetakis, A. Anastasiadis, K. Pitilakis, A comparison of material damping measurements in resonant column using the steady-state and free-vibration decay methods, Soil Dynamics and Earthquake Engineering, 74 (2015) 10-13.
[26] ASTM, Standard test methods for modulus and damping of soils by the resonant-column method, in, 2007.
[27] B. Madhusudhan, K. Senetakis, Evaluating use of resonant column in flexural mode for dynamic characterization of Bangalore sand, Soils and Foundations, 56(3) (2016) 574-580.
[28] K. Ishihara, Soil behaviour in earthquake geotechnics, 1996.
[29] B. Das, G. Ramana, Principles of soil dynamics, 2nd edn. Cengage Learning, 2010.