رفتار مقاومت سیکلی و نشست خاکهای شنی اشباع با تراکم بالا

نوع مقاله : مقاله پژوهشی

نویسنده

دانشیار، مرکز تحقیقات راه، مسکن و شهرسازی، تهران، ایران

چکیده

این مقاله، مقاومت سیکلی و نشست خاکهای شن‌دار با تراکم بالا تحت شرایط زهکشی‌نشده با استفاده دستگاه سه‌محوری بزرگ‌مقیاس را ارائه می‌دهد. براساس نتایج، معیار گسیختگی برای مصالح شنی متراکم در 15 تا 50 سیکل بارگذاری با توجه درصد ریزدانه و تنشهای برشی سیکلی ناشی از تکانهای زلزله به صورت زیر تعریف می‌شود: الف) ایجاد 2درصد کرنش محوری تجمعی دائمی،PAAS، حتی برای مقدار نسبت اضافه فشار آب حفره‌ای تولیدی به تنش محدودکننده موثر،ru، کمتر از 0/8برای مصالح با درصد ریزدانه بیش از 14درصد، ب) ایجاد کرنش‌محوری دوبرابر‌دامنه، DAAS، برابر 2درصد برای نسبت تنش‌سیکلی بیش 0/45و ایجاد ru برابر و بیش از یک. در نمونه شنی متراکم چنانچه در سیکل اول، PAAS یا DAAS برابر با 0/5-0/45درصد یا ru بین 0/25-0/20 است، معمولاً در کمتر از 50 سیکل، روانگرایی اولیه (ru≥1) یا گسیختگی با ایجاد کرنش محوری حدود 2درصد رخ می‌دهد. مقاومت سیکلی نمونه شنی با ریزدانه بیشتر از 14درصد کمتر از مقادیر نظیر نمونه با ریزدانه کمتر از 4درصد است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Cyclic Strength and Settlement Behaviors of High Compacted Saturated Gravelly Soils

نویسنده [English]

  • Ata Aghaei Araei
Associate Professor, Road, Housing and Urban Development Research Center, Tehran, Iran.
چکیده [English]

This paper presents the undrained cyclic strength and settlememt behaviors of high compacted saturated gravelly soils using large-scale triaxial equipment. Based on the results, the failure critera for dense gravel materials in 15-50 loading cycles may be adopted, considering the fine content and cyclic shear stress due to earthquake shaking, as follows: (a) inducing 2% permanent accumulated axial strain (PAAS) for ru<0.8 (i.e. ratio of maximum excess pore-water pressure to effective confining pressure), for the specimen with fine content higher than 14%, (b) inducing 2% double amplitude axial strain (DAAS) for ru≥1 for isotropic consolidated dense gravelly specimen containing fine grain smaller than 4% under very high stress ratio as much as 0.45 and higher. For high copmpacted gravelly specimen, when in the first cycle of loading, ru and DAAS are higher than 0.20-0.25% and 0.4-0.5%, respectively, the initial liquefaction (ru>1) or failure may be occurred in less than 50 cycles by inducing PAAS or DAAS for about 2%. Cyclic strength of gravelly materials containing fine contain higher than 14% are smaller than that of the specimen containing fine grain smaller than 4%.

کلیدواژه‌ها [English]

  • Compacted-Gravel
  • Triaxial
  • Isotropically
  • Anisotropically
  • Cyclic Strength
  • Failure
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