بررسی پارامترهای مؤثر بر نشست و گسترش جانبی شالوده‌های سطحی واقع بر لایه‌های خاکی شیب‌دار قابل روانگرا

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده مهندسی و فناوری، دانشگاه مازندران، بابلسر، ایران

چکیده

جابجایی­ های ساختمان در اثر وقوع پدیده‌ی روانگرایی در زلزله‌های گذشته باعث بروز خسارات قابل توجه‌ای به سازه‌ها و زیر ساخت‌های آن‌ها شده است. با وجود انجام مطالعات مختلف توسط پژوهشگران، همچنان رویکرد جامعی برای ارزیابی هم­زمان اثر گسترش جانبی و نشست سازه بر روی شالوده‌های سطحی وجود ندارد. در این پژوهش سعی شده است جابجایی­های شالوده‌ی سطحی بر روی لایه‌های خاکی شیب‌دار با درصد تراکم‌های مختلف به صورت پارامتریک با استفاده از شبیه‌سازی سه ‌بعدی به روش المان محدود مورد بررسی قرار گیرد. بدین منظور، ابتدا مدل عددی با نتایج آزمایش سانتریفیوژ صحت­ سنجی شده و سپس پارامترهایی نظیر: شیب زمین، تراکم لایه‌ی روانگرا، سطح آب زیرزمینی، فشار تماسی و نسبت طول به عرض شالوده مورد بررسی قرار گرفته است. نتایج نشان می‌دهد که با افزایش اندک در شیب زمین از 0 به 2 درجه میزان جابجایی‌های افقی به دلیل گسترش جانبی به­ شدت افزایش می­یابد. افزایش تراکم لایه‌ی روانگرا در لایه‌های خاکی شیب‌دار متوسط نشست شالوده را کاهش داده و در مقابل میزان دوران شالوده را افزایش می‌دهد. کاهش سطح آب زیرزمینی نیز باعث کاهش نشست می‌شود، اما در برخی از موارد به خصوص در مدل‌های بدون سازه میزان نشست را افزایش می‌دهد. دلیل آن این است که افزایش وزن مؤثر مانند یک اضافه تنش روی خاک عمل کرده و تنش‌های برشی منتقل شده به لایه‌ی روانگرا را افزایش می­دهد، که در نتیجه‌ کرنش‌های حجمی خاک تقویت شده و نشست در نواحی دور از سازه افزایش جزئی پیدا می­ کند. همچنین شالوده‌ها با نسبت طول به‌ عرض بزرگ‌تر، به علت ایجاد کرنش‌های برشی کوچک‌تر نشست‌های کمتری دارند.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Investigation of Effective Parameters on the Settlement and Lateral Spreading of Shallow Foundations on the Sloping Liquefiable Soil

نویسندگان [English]

  • Sina Pourabbasi
  • Ali Asgari
University of Mazandaran
چکیده [English]

The settlement and lateral spreading of the building due to the occurrence of the liquefaction phenomenon in previous earthquakes have caused significant damage to structures and their infrastructure. Numerous studies have been performed to evaluate the settlement of shallow foundations located on the liquefiable soils as a horizontal model. In fact, in most cases, there is a mild slope in the layers that can be affected by the settlement and lateral spreading of the foundation. In this research, the displacements of the structure and shallow foundation/ground surface on the sloping liquefiable three-layers soil with different relative densities have been investigated parametrically, applying three-dimensional finite element (FE) simulations using OpenseesSP. The layers are subjected to the realistic destructive event with scaled peak ground acceleration of 0.35g. A multi-yield-surface plasticity model was selected for the analysis conducted in this research based on constitutive laws applicable to all types of soils. The purpose of this study is to investigate the effect of parameters including the slope of soil layers, the density of liquefiable layer, groundwater level, foundation contact pressure, and length to width ratio of the foundation on the settlement and lateral spreading of the liquefiable sloping model. The results are shown that increasing the slope of the ground increases the difference between the settlement of the two sides of the foundation and increases the lateral displacements. Decreasing the relative density of the liquefiable layer increases the excess pore water pressure and the settlement of shallow foundation. The results also are shown that lower the groundwater level is increased the effective stress and reduces the vertical and horizontal displacements. Besides, increasing the contact pressure is amplified the foundation of static and dynamic volumetric strains and increases the settlements. Shallow foundations with larger length-to-width ratios experience lower settlements due to smaller shear strains.

کلیدواژه‌ها [English]

  • Lateral spreading
  • Settlement
  • Sloping model
  • Three-dimensional simulation
  • Finite element method

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نشریه مهندسی عمران امیرکبیر
دوره 54، شماره 3
خرداد 1401
صفحه 1191-1216

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