مقایسه رفتار خاک‏ های ماسه‌ای متراکم داخل و خارج باند برشی در آزمایش برش مستقیم با استفاده از روش المان مجزای دوبعدی

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده مهندسی عمران، دانشگاه یزد، یزد، ایران

چکیده

باند برشی از مهم‌ترین ویژگی‌های رفتاری خاک‌های دانه‌ای است که در واقع حاصل موضعی شدن تغییر شکل‌ها تحت بارهای اعمال شده بر نمونه خاک است. مطالعات بسیاری بر روی پدیده تشکیل باند برشی انجام شده است، لیکن به مقایسه رفتار خاک داخل و خارج از باند برشی کم‌تر پرداخته شده است.  هدف از مطالعه حاضر مقایسه رفتار خاک داخل و خارج باند برشی در آزمون برش مستقیم در مقیاس‏های ماکرو و میکرو با استفاده از روش المان مجزا دوبعدی است. بدین منظور ابتدا با مقایسه نتایج شبیه‏سازی و تجربی، پارامترهای ماده در مقیاس میکرو کالیبره شدند. سپس یک مطالعه پارامتری با انجام 9 آزمون برش مستقیم با تنش‏های قائم متفاوت بر روی سه نمونه خاک با تراکم‏های متفاوت انجام شد. در این مطالعه پارامتری، کمیت‏هایی شامل تنش برشی، پوکی، چرخش ذرات، عدد تماس و انرژی پلاستیک بین‏ذره‏ای داخل و خارج باند برشی در طول آزمون اندازه‏گیری شدند. نتایج مطالعه حاضر نشان داد که چرخش ذرات در انتهای آزمون به طور متوسط داخل باند برشی 5 تا 17 برابر بزرگ‌تر از چرخش ذرات خارج باند برشی هستند. همچنین نتایج نشان داد که انرژی زوال یافته در انتهای آزمون به طور متوسط داخل باند برشی 12 تا 96 برابر بزرگ‌تر انرژی‏های زوال یافته خارج باند برشی هستند. علاوه بر این، نتایج نشان داد که اعداد تماس در انتهای آزمون به طور متوسط داخل باند برشی 3 تا 19 درصد کم‌تر اعداد تماس خارج باند برشی هستند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Comparing the Behavior of Dense Sandy Soils Inside and Outside the Shear Band in the Direct Shear Test Using the Two-dimensional Discrete Element Method

نویسندگان [English]

  • Ahmadreza Javid
  • Mohammad Hazeghian
  • Mohammad Abdoli
Yazd University
چکیده [English]

Shear banding is one of the most significant behavioral characteristics of granular soils, which is actually the result of the localization of deformations under loads applied to the soil sample. Many studies have been conducted on the phenomenon of shear band formation. However, the comparison of the behavior of soil inside and outside the shear band has received less attention. The purpose of this study is to compare the behavior of soil inside and outside the shear band in the direct shear test at macro and micro scales using the two-dimensional discrete element method. To achieve this, the micro-material parameters were first calibrated through the comparison of simulation and experimental results. Then a parametric study was conducted by performing 9 direct shear tests with different vertical stresses on three soil samples with different relative densities. During the tests, quantities such as shear stress, porosity, particle rotation, coordination number, and interparticle plastic energy were measured both inside and outside the shear band. The results of the present study showed that the particle rotations at the end of the test inside the shear band were 5 to 17 times higher than those outside the shear band. Furthermore, the results showed that the dissipated energies at the end of the test inside the shear band were 12 to 96 times larger than those outside the shear band. Moreover, it was found that the coordination numbers at the end of the test inside the shear band were on average 3-19% lesser than those outside it.

کلیدواژه‌ها [English]

  • Direct Shear Test
  • Discrete Element Method
  • Sandy Soil
  • Inside and Outside of The Shear Band
  • PFC2D
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