مقایسه رفتار دینامیکی ماسه های کربناتی هرمز و سیلیکاتی بابلسر در شرایط یکسان

نوع مقاله : Articles

نویسندگان

1 پژوهشگاه بین المللی زلزله شناسی و مهندسی زلزله

2 دانشگاه شهرکرد

3 دانشگاه سمنان

چکیده

مرور مطالعات گذشته نشان می­دهد که بخش زیادی از تحقیقات صورت گرفته بر رفتار خاک­های سیلیکاتی متمرکز بوده و خاک­های کربناتی کمتر مورد توجه قرار گرفته‌اند. از طرفی بخش­های وسیعی از کره زمین از جمله نواحی جنوبی کشورمان پوشیده از خاک­ها و رسوبات کربناتی است. ازاین‌رو ارزیابی رفتار این نهشته­ها در مقایسه با خاک­های سیلیکاتی از اهمیت بالایی برخوردار است. در این مطالعه، پارامترهای دینامیکی ماسه­های کربناتی هرمز و سیلیکاتی بابلسر تحت شرایط یکسان و با استفاده از مطالعات آزمایشگاهی مورد ارزیابی قرار گرفته است. مدول برشی و نسبت میرایی ماسه­های مذکور در دامنه­های کرنش برشی کوچک و بزرگ به ترتیب با انجام آزمایش­های ستون تشدید و سه­محوری سیکلی محاسبه گردید. بر اساس نتایج حاصل، افزایش فشار محدودکننده، افزایش مدول برشی و کاهش نسبت میرایی ماسه­های کربناتی و سیلیکاتی را به دنبال داشته است. مقایسه‌ی پارامترهای دینامیکی ماسه­های مورد آزمایش بیانگر آن است که مدول برشی ماسه‌ی هرمز بیشتر از ماسه‌ی بابلسر است. همچنین در شرایط یکسان، نسبت میرایی ماسه‌ی بابلسر فراتر از ماسه‌ی هرمز حاصل شده است. نتایج آزمایش­ها با روابط محققین برای ارزیابی رفتار دینامیکی ماسه­ها مقایسه شدند. این مقایسه حاکی از آن است که روابط موجود قادر به ارزیابی دقیق رفتار دینامیکی ماسه‌ی کربناتی هرمز نبوده و نیاز برای ارائه­ی روابط ویژه برای این خاک وجود دارد. Comparing Dynamic Behavior of Hormuz Calcareous and Babolsar Siliceous Sands under Identical Conditions Yaser Jafarian, Hamed Javdanian, Abdolhosein HaddadKnowledge of the dynamic behavior curves of soils is important for designing various geotechnical structures subjected to different kinds of vibrations, including earthquakes. Reviewing the previous studies on soil dynamic behavior shows that most of the studies have focused on the siliceous soils. Geological studies suggest that vast areas of the earth in the tropical regions are covered by calcareous deposits. Large areas of the southern Iran, which are seismic-prone based on the recent earthquake activities, are also covered by calcareous soils. Foundation problems associated with carbonate soil deposits, particularly as experienced by the offshore hydrocarbon industry have led to significant research focused on understanding the behavior of these soils. Origination of calcareous soils from processes and minerals different than those known for the silicate soils clarifies the necessity for comprehensive research on geotechnical properties of such soils. The wide variation of the origin of calcareous soils, due to their offshore locations and the related fauna that make their formation, merit more research into the behavior of these soils from various regions.In the current research, shear modulus and damping ratio of Hormuz calcareous sand and Babolsar siliceous sand were measured and compared. An identical grains size distribution curve was synthetically attained for the tested sands. The soils are classified as poorly graded sand (SP) according to the USCS (ASTM D2487). The shear modulus and damping ratio values were calculated at small and large shear strains using resonant column and cyclic triaxial tests. The calcareous and siliceous soil specimens were tested by a fixed-free type of resonant column apparatus (SEIKEN model). By using the resonant column apparatus, shear modulus and damping ratio of the calcareous and siliceous sands were measured for the shear strain amplitude ranging from about 10-4 % to 10-2 %. The cyclic triaxial tests were conducted using a fully automated GDS triaxial testing apparatus. The cyclic tests were done on the samples with shear strain amplitudes ranging from about 10-2 % to 1 %. The procedure used to perform the resonant column and cyclic triaxial tests was the multi-stage strain-controlled loading under undrained condition.The results for both calcareous and siliceous sands indicate that the shear modulus (G) decreases and damping ratio (D) increases with an increase in shear strain amplitude (γ), as expected. Moreover, the shear modulus of tested  soils increases with the increase of effective confining pressure (σ'0). Further, the tests results indicate that the increased amount of effective confining pressure leads to the smaller damping ratio for the Hormuz and Babolsar sands. The shear modulus of Hormuz calcareous sand is higher than that of the Babolsar siliceous sand while grains size distribution, effective confining pressure, and void ratio of both soils were identical. It is evident from the resonant column and cyclic triaxial tests that the Hormuz calcareous sand has lower values of damping ratio (D) in comparison to the Babolsar siliceous sand. Finally, dynamic behavior curves of the studied sands are compared with the available relationships. These comparisons indicate that the available relationships are unable to accurately assess behavior of the tested calcareous sand. Keywords: Calcareous Sand; Siliceous Sand; Shear Modulus; Damping Ratio; Experimental Studies

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مراجع

Ishihara, K. (1996) Soil Behavior in Earthquake Geotechnics. Oxford Science Publications, pp. 350.
Jafarian, Y., Haddad, A., and Javdanian, H. (2015) Comparing the shear stiffness of calcareous and silicate sands under dynamic and cyclic straining. 7th International Conference of Seismology and Earthquake Engineering (SEE7), Tehran, Iran.
Zhang, J., Andrus, R.D., and Juang, C.H. (2005) Normalized shear modulus and material damping ratio relationships. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 131(4), 453-464.
Jafarian, Y., Haddad, A., and Javdanian, H. (2014) Predictive model for normalized shear modulus of cohesive soils. Acta Geodynamica et Geomaterialia, 11(1), 89-100.
Javdanian, H., Jafarian, Y., and Haddad, A. (2015) Predicting damping ratio of fine grained soils using soft computing methodology. Arabian Journal of Geoscienecs, 8(6), 3959-3969.
Seed H.B. and Idriss I.M. (1970) Soil Moduli and Damping Factors for Dynamic Analysis. Report No. EERC 70-10, University of California, Berkeley.
Seed, H.B., Wong, R.T., Idriss, I.M., and Tokimatsu, K. (1986) Moduli and damping factors for dynamic analyses of cohesionless soils. J. Geotech. Eng., ASCE, 112(11), 1016-1032.
Clayton, C.R.I. (2011) Stiffness at small strain: research and practice. Geotechnique, 61(1), 5-37.
Senetakis, K., Anastasiadis, A., and Pitilakis, K. (2012) The small-strain shear modulus and damping ratio of quartz and volcanic sands. Geotechnical Testing Journal, ASTM, 35(6), 964-980.
Holmes, A. (1978) Principles of Physical Geology. Nelson, London, pp. 730.
Kwag, J.M., Ochiai, H., and Yasufuku, N. (1999) Yielding stress characteristics of carbonate sand in relation to individual particle fragmentation strength. Proceedings of the 2nd International Conference on Engineering for Soil Sediments, Bahrain, 1, 79-86.
Ong, S.E., Joer, H.A., and Randolph, M.F. (1999) Frictional behavior in calcareous soils. Proceedings of the 2nd International Conference on Engineering for Soil Sediments, Bahrain, 1, 219-228.
Coop, M.R. and Airey, D.W. (2003) ‘Carbonate sands’. In: Characterization and Engineering Properties of Natural Soils, Tan, T.S., Phoon, K.K., Hight, D.W., Leroueil, S. (eds), pages 1049-1086.
Coop, M.R., Sorensen, K.K., Freitas, T.B., and Georgoutsos, G. (2004) Particle breakage during shearing of a carbonate sand. Geotechnique, 54(3), 157-163.
Sharma, S.S. and Fahey, M. (2004) Deformation characteristics of two cemented calcareous soils. Canadian Geotechnical Journal, 41, 1139-1151.
Lenart, S. (2006) Deformation characteristics of lacustrine carbonate silt in the Julian Alps. Soil Dynamics and Earthquake Engineering, 26, 131-142.
Shahnazari, H. and Rezvani, R. (2013) Effective parameters for the particle breakage of calcareous sands: An experimental study. Engineering Geology, 159, 98-105.
Shahnazari, H., Salehzadeh, H., Rezvani, R., and Dehnavi, Y. (2014) The effect of shape and stiffness of originally different marine soil grains on their contractive and dilative behavior. KSCE J. Civil Eng., 18(4), 975-983.
Hassanlourad, M., Salehzadeh, H., and Shahnazari, H. (2008) Dilation and particle breakage effects on the shear strength of calcareous sands based on energy aspects. Int J Civil Engineering, 6(2), 108-119.
Jafarian, Y. and Rakhshandeh, M. (2014) Laboratory study on cyclic behaviour and pore water pressure generation of Boushehr calcareous sand. Modares Civil Engineering Journal, 15(3), 37-50.
Jafarian, Y., Haddad, A., and Javdanian, H. (2016) Estimating the shearing modulus of Bushehr calcareous sand using resonant column and cyclic triaxial experiments. Modares Civil Engineering Journal, 15(4), 9-19.
Kramer, S.L. (1996) Geotechnical Earthquake Engineering. Prentice Hall, 670p.
Cho, G.C., Dodds, J., and Santamarina, J.C. (2006) Particle shape effects on packing density, stiffness, and strength: natural and crushed sands. J. Geotech. Geoenviron. Eng., 132(5), 591-602.
Wichtmann, T. and Triantafyllidis, T. (2013a) Effect of uniformity coefficient on G/Gmax and damping ratio of uniform to well-graded quartz sands. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 139(1), 59-72.
Senetakis, K., Anastasiadis, A., and Pitilakis, K. (2013a) Normalized shear modulus reduction and damping ratio curves of quartz sand and rhyolitic crushed rock. Soils and Foundations, 53(6), 879-893.
Hardin, B.O. and Drnevich, V.P. (1972) Shear modulus and damping in soils; measurement and parameter effects. J. Soil Mech. Found Div., ASCE, 98(6), 603-624.
Ishibashi, I. and Zhang, X. (1993) Unified dynamic shear moduli and damping ratios of sand and clay. Soils and Foundations, 33(1), 182-191.
Rollins, K.M., Evans, M.D., Diehl, N.B., and Daily, W.D. (1998) Shear modulus and damping relationships for gravels. J. Geotech. Geoenviron. Engineering, ASCE, 124(5), 398-405.

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