اثر ریزدانه‌ها بر کرنش برشی آستانه ماسه های اشباع

نوع مقاله : مقاله پژوهشی

نویسندگان

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

2 استادیار، دانشکده مهندسی عمران، دانشگاه آزاد اسلامی واحد علوم و تحقیقات، تهران، ایران

چکیده

یکی از خصوصیات مهم ماسه‌های اشباع تحت بار‌های سیکلی کرنش برشی آستانه ( ) می‌باشد. کرنش برشی آستانه بمنظور بررسی فشار منفذی ایجاد شده ناشی از بارهای زلزله، ماشین آلات ارتعاشی وکلیه بارهای سیکلی موقت یا همیشگی وارده بر خاک تعیین می‌شود. بر اساس مطالعات انجام شده کرنش برشی آستانه میزان کرنشی است که تا قبل از آن فشار آب حفره‌ای در حالت اشباع و نوسانات حجمی در حالت خشک دستخوش تغییر نشوند. با افزایش مقدار کرنش برشی به بیش از  تغییرات در فشار منفذی معنی‌دار شده و ریز ساختار خاک دستخوش تغییر می‌شود. در این تحقیق نمونه‌هایی از ماسه‌های حاوی ریزدانه‌های چسبنده و غیر چسبنده با استفاده از روش تراکم کاهش یافته مرطوب تهیه شده و با انجام آزمایش‌های سه محوری سیکلی کنترل کرنش در محدوده کرنش‌های کوچک، اثر نوع و مقدار ریزدانه‌ها بر کرنش برشی آستانه این خاک‌ها مورد بررسی قرار گرفته است. نتایج آزمایش‌ها نشان می‌دهند با افزایش مقدار ریزدانه‌های چسبنده به بیش از 20 درصد، کرنش برشی آستانه نیز به میزان قابل توجهی نسبت به ماسه تمیز افزایش می‌یابد. همچنین افزایش ریزدانه‌های غیر چسبنده، ابتدا افزایش و سپس کاهش کرنش برشی آستانه را نشان می‌دهد.

کلیدواژه‌ها

عنوان مقاله [English]

The Effect of Fines on Threshold Shear Strain of Saturated Sands

نویسندگان [English]

  • Seyed magdldin Mir Mohammad Hosseini 1
  • Mehdi Derakhshandi 2
1 Professor, Department of Civil & Environmental Engineering, Amirkabir University of Technology, Tehran, Iran.
2 Assistant professor, Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
چکیده [English]

Threshold shear strain is one of the basic parameters of soil during cyclic loading condition. The threshold shear strain should be determined for evaluating pore water pressure generation due to earthquake, vibrating machine and all the cyclic loading which apply permanently or temporary on the soil. According to many scientific researches, the threshold shear strain is the strain, which there is no pore water pressure generation at the saturated soils and no volume changes at the dry conditions during cyclic loading. By increasing the shear strain more than threshold shear strain ( ), pore pressure increase is noticeable at the saturated soil and the soil microstructure starts to change.  In this study, the effects of plastic and non-plastic fines on the threshold shear strain of saturated sands were evaluated by performing a number of cyclic triaxial tests with strain control method at small shear strain.  All the specimens contained 0%, 10%, 20% and 30% plastic and non-plastic fines prepared by wet tamping undercompaction method. As a result, by increasing plastic fines more than 20%, threshold shear strain increased significantly.  Moreover, by increasing non-plastic fines, threshold shear strain fluctuated. It first increased and then decreased.

کلیدواژه‌ها [English]

  • Threshold Shear Strain
  • Saturated Sands
  • Plastic and Non-plastic Fines
  • Pore Pressure
  • Strain-controlled Cyclic Triaxial Test

مراجع

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