بررسی خصوصیات مکانیکی سنگ نمک با تکیه بر ریزساختار آن

نوع مقاله: مقاله پژوهشی

نویسندگان

1 گروه زمین شناسی، دانشکده علوم، دانشگاه اصفهان، اصفهان، ایران

2 استاد گروه زمین شناسی مهندسی دانشگاه اصفهان

3 سازمان زمین شناسی، تبریز، ایران

4 گروه زمین شناسی، دانشگاه اصفهان، اصفهان، ایران

چکیده

در این مقاله تأثیر ریزساختار اولیه سنگ نمک بر رفتار دگرشکلی آن مورد بررسی قرار گرفت. نمونه‌های مورد مطالعه از دیاپیر نمکی دهکویه واقع در 27 کیلومتری شهرستان لار در استان فارس برداشت شدند. ریزساختار اولیه دو نمونه متعلق به بخش‌های فوقانی دیاپیر و یک نمونه متعلق به قسمت میانی ساقه دیاپیر به روش پراش الکترون‌های برگشتی در دانشگاه اتاگو نیوزیلند مطالعه شد. اکثر دانه‌ها در نمونه متعلق به ساقه دارای دگرشکلی داخلی هستند، اندازه دانه‌های آن کوچکتر و فراوانی مرزهای کم زاویه در آن بیشتر است. مقاومت تراکمی تک محوری، مدول الاستیک و مقاومت کششی این نمونه کمتر و کرنش آنی، کرنش خزشی و نرخ کرنش آن تحت تنش محوری 12 مگاپاسکال بیشتر از نمونه‌های متعلق به بخش‌های فوقانی دیاپیر است که می‌تواند در نتیجه بیشتر بودن درصد تخلخل و منافذ کوچک میکروسکوپی در امتداد مرز دانه‌ها در این نمونه باشد. در مقابل ساز و کار دگرشکلی غالب در نمونه‌های متعلق به بخش‌های فوقانی دیایپر رشد دانه‌ها در اثر مهاجرت مرز دانه‌ها بوده‌است. این سازوکار سبب حذف منافذ و نقص‌های موجود در دانه‌ها می‌شود. از این رو این نمونه‌ها از مقاومت و مدول الاستیک بالاتری برخوردار بوده و دگرشکلی پلاستیک دانه‌ها در حین آزمون‌ها مکانیکی با سهولت بیشتری انجام می‌شده‌است. در کل نتایج این تحقیق پیشنهاد می‌کند که بررسی ریزساختار سنگ نمک و چگونگی رفتار آن تحت شرایط بارگذاری مختلف در درک رفتار مخازن ذخیره ایجاد شده در نمک مهم و اساسی است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigation of mechanical properties of salt rock based on its microstructure

نویسندگان [English]

  • Hadiseh Mansouri 1
  • Rasoul Ajalloeian 2
  • Ramin Elyaszadeh 3
  • Alireza Mansouri 4
1 Department of Geology, Faculty of Sciences, University of Isfahan, Isfahan, Iran
2 Professor, Department of Engineering Geology, Isfahan University
3 Geological Survey of Iran, Tabriz, Iran
4 Department of Geology, Faculty of Sciences, University of Isfahan, Iran,
چکیده [English]

In this paper, initial microstructure effect of salt rock on its deformation behavior was investigated. Studied samples were taken from Deh Kuyeh salt diapir located at about 27 km NE of Lar city, Fars province. Initial microstructure of two samples from the top of the fountain and one sample from middle part of the diapiric stem were studied by electron backscatter diffraction at Otago University, New Zealand. A slight difference was observed between the initial microstructure of the samples. In the sample from the stem, most grains had been internally deformed, and the grain size is smaller and frequency of low angle boundaries is higher than those in the sample from top of the fountain. The uniaxial compressive strength, elastic modulus and tensile strength values of this sample are lower and its elastic strain, creep strain and creep rate under axial stress of 12 MPa are higher than those in the sample from top of the fountain which can be due to the higher percent of microscopic pores along its grain boundaries. In contrast, the dominant deformation mechanism in the samples from top of the fountain is the grain growth via grain boundary migration. This mechanism removes voids and defects within the grains and along the grain boundaries. Therefore, these samples have higher values of strength and elastic modulus and their grains more easily deformed plastically during mechanical tests.

کلیدواژه‌ها [English]

  • Salt rock
  • Microstructure
  • Mechanical properties
  • Electron backscatter diffraction

Adams, B.L., Dingley, D.J., Kunze, K., Wright, S.I., 1994. Orientation imaging microscopy: new possibilities for microstructural investigations using automated BKD analysis, Materials Science Forum. Trans Tech Publ, pp. 31-42.

Basu, A., Mishra, D., Roychowdhury, K., 2013. Rock failure modes under uniaxial compression, Brazilian, and point load tests. Bulletin of Engineering Geology And The Environment, 72: 457-475.

Bestmann, M., Piazolo, S., Spiers, C.J., Prior, D.J., 2005. Microstructural evolution during initial stages of static recovery and recrystallization: new insights from in-situ heating experiments combined with electron backscatter diffraction analysis. Journal of Structural Geology, 27: 447-457.

Callister, W.D., Rethwisch, D.G., 1991. Materialsscience and engineering: an introduction. Wiley New York,

Cristescu, N., Hunsche, U., 1998. Time effects in rock mechanics. Wiley New York.

Desbois, G., Závada, P., Schléder, Z., Urai, J.L., 2010. Deformation and recrystallization mechanisms in actively extruding salt fountain: Microstructural evidence for a switch in deformation mechanisms with increased availability of meteoric water and decreased grain size (Qum Kuh, central Iran). Journal of Structural Geology, 32: 580-594.

Ding, J., Chester, F.M., Chester, J.S., Xianda, S., Arson, C., 2017. Microcrack Network Development in Salt-Rock During Cyclic Loading at Low Confining Pressure. Georgia Institute of Technology.

Duncan, E.S., Lajtai, E.Z., 1993. The creep of potash salt rocks from Saskatchewan. Geotechnical & Geological Engineering, 11: 159-184.

Hansen, F.D., Mellegard, K.D., Senseny, P.E., 1984. Elasticity and strength of ten natural rock salts, Proc First Conf. on the Mechanical Behavior of Salt, pp. 71-83.

Jie, C., Junwei, Z., Song, R., Lin, L., Liming, Y., 2015. Determination of Damage Constitutive Behavior for Rock Salt Under Uniaxial Compression Condition with Acoustic Emission. Open Civil Engineering Journal, 9: 75-81.

Liang, W.-g., Yang, C.-h., Zhao, Y.-s., Dusseault, M., Liu, J., 2007. Experimental investigation of mechanical properties of bedded salt rock. International Journal of Rock Mechanics and Mining Sciences, 44: 400-411.

Liang, W., Zhao, Y., Xu, S., Dusseault, M., 2011. Effect of strain rate on the mechanical properties of saltrock. International Journal of Rock Mechanics and Mining Sciences, 48: 161-167.

Liu, Z., Xie, S., Shao, J.-F., Conil, N., 2015. Effects of deviatoric stress and structural anisotropy on compressive creep behavior of a clayey rock. Applied Clay Science, 114: 491-496.

Motta, G.E., Pinto, C.L.L., 2014. New constitutive equation for salt rock creep. Rem: Revista Escola de Minas, 67: 397-403.

Pennock, G., Drury, M., Peach, C., Spiers, C., 2006. The influence of water on deformation microstructures and textures in synthetic NaCl measured using EBSD. Journal of Structural Geology, 28: 588-601.

Piazolo, S., Bestmann, M., Prior, D., Spiers, C., 2006. Temperature dependent grain boundary migration in deformed-then-annealed material: observations from experimentally deformed synthetic rocksalt. Tectonophysics, 427: 55-71.

Prior, D., 1999. Problems in determining the misorientation axes, for small angular misorientations, using electron backscatter diffraction in the SEM. Journal of microscopy, 195: 217-225.

Raj, R., Ashby, M., 1975. Intergranular fracture at elevated temperature. Acta metallurgica, 23: 653-666.

Schléder, Z., Urai, J.L., 2007. Deformation and recrystallization mechanisms in mylonitic shear zones in naturally deformed extrusive Eocene–Oligocene rocksalt from Eyvanekey plateau and Garmsar hills (central Iran). Journal of Structural Geology, 29: 241-255.

Spiers, C., Schutjens, P., Brzesowsky, R., Peach, C., Liezenberg, J., Zwart, H., 1990. Experimental determination of constitutive parameters governingcreep of rocksalt by pressure solution. Geological Society, London, Special Publications, 54: 215-227.

Sriapai, T., Walsri, C., Fuenkajorn, K., 2012. Effect of temperature on compressive and tensile strengths of salt. ScienceAsia, 38: 166-174.

Sugino, Y., Ukai, S., Leng, B., Oono, N., Hayashi, S., Kaito, T., Ohtsuka, S., 2012. Grain boundary related deformation in ODS ferritic steel during creep test. Materials Transactions, 53: 1753-1757.

Ter Heege, J., De Bresser, J., Spiers, C., 2005. Dynamic recrystallization of wet synthetic polycrystalline halite: dependence of grain size distribution on flow stress, temperature and strain. Tectonophysics, 396: 35-57.

Wang, J., Liu, X., Zhao, B., Song, Z., Lai, J., 2016. Experimental investigation and constitutivemodel for lime mudstone. SpringerPlus, 5: 1634.

Wilkosz, P., Burliga, S., Grzybowski, Ł., Kasprzyk, W., 2012. Comparison of internal structure and geomechanical properties in horizontally layered Zechstein rock salt. Mechanical Behavior of Salt, 7: 89-96.

Xu, S., Wu, X.-J., Koul, A., Dickson, J., 1999. An intergranular creep crack growth model based on grain boundary sliding. Metallurgical and Materials Transactions A, 30: 1039-1045.

Yang, C., Daemen, J., Yin, J.-H., 1999. Experimental investigation of creep behavior of salt rock. International Journal of Rock Mechanics and Mining Sciences, 36: 233-242.

Yang, J.-L., Zhang, Z., Schlarb, A.K., Friedrich, K., 2006. On the characterization of tensile creep resistance of polyamide 66 nanocomposites. Part II: Modeling and prediction of long-term performance. Polymer, 47: 6745-6758.

Závada, P., Desbois, G., Schwedt, A., Lexa, O., Urai, J.L., 2012. Extreme ductile deformation of fine-grained salt by coupled solution-precipitation creep and microcracking: Microstructural evidence from perennial Zechstein sequence (Neuhof salt mine, Germany).