20942

۲۰۹۴۲

بررسي پايداري خاكريز مسلح شده با ژئوسنتتيك در حضور بار قائم هارمونيك به روش عددي

كارشناسي ارشد

خاك و پي

۹۵-۹۸

۱۳۹۸/۴/۲۲

دكترحسين صالح زاده - دكتر علي اكبر حشمتي

دكتر عليرضا سعيدي عزيزكندي

عمران

احداث سازه هاي مختلف عمراني روي خاكهاي ضعيف يا نرم، غالبا امري اجتناب ناپذير است. در اين شرايط انتخاب روش هاي مناسب جهت بهبود خصوصيات فيزيكي و مكانيكي و مقاومتي خاك ضروري است . در همين راستا در حوزه ساخت خاكريز به منظور افزايش پايداري و كاهش نشست از المان مسلح كننده ژئوگريد در ارتفاع خاكريز استفاده مي شود. با توجه به پيشرفت روزافزون علم در زمينه قطارهاي سريع السير در حمل درون شهري و برون شهري مسافرين، بررسي پايداري خاكريزها حائز اهميت است. در رساله حاضر ابتدا كار صورت گرفته در آزمايشگاه در نرم افزار آباكوس مدلسازي شده و نتايج با نتايج بدست آمده از كار آزمايشگاهي موجود و گزارش شده در منابع مقايسه شده و سپس اثر پارامترهاي مختلف مثل تعداد و فاصله بهينه لايه هاي ژئوگريد، اثر فركانس و دامنه بارگذاري هارمونيك و تغييرات مدول الاستيسيته ژئوگريد بر روي ضريب اطمينان و نشست مطالعه شده اند. براساس مطالعات عددي در رساله حاضر نتيجه گرفته شد كه افزايش ضريب اطمينان پايداري خاكريز با كاهش دامنه بارگذاري و افزايش فركانس و افزايش مدول الاستيسيته ژئوگريد اتفاق مي افتد. در ارتباط با نشست در طول بارگذاري هارمونيك نيز دامنه بارگذاري تاثير مستقيم بر روي نتايج دارد در حالي كه تغييرات نشست نسبت به تغييرات فركانس بارگذاري و مدول الاستيسيته ژئوگريد چشم گير نيست.

1398/05/22

Stability analysis of geosynthetic-reinforced embankment under vertical harmonic loading with numerical simulation

8/13/2019 12:00:00 AM

The construction of various civil structures on weak or soft soils is often unavailabe. In this situation, selecting suitable methods to improve the physical, mechanical and strength properties of the soil is necessary. In order to improve and reinforce the soil in past decades, various improvement methods have been used that are divided into two categories: mechanical and chemical. Soils are very resistant to compressive stress, but in the face of tensile stresses they are reinforced by reinforcements. As a result, the outcome is a composite structure with a wide range of resistance,also in zone of structure embankment to increase the stability and reduce the settlement,geogrids are used. The IRC Committee defines the embankment for any earth structure that is higher than the natural level of the ground for elevating the height of the road or rail. Stabilization of these embankments is one of the important issues in civil engineering. The importance of this issue can be seen from the damage caused by earthquakes and the large volume of big and costly projects deal with the slope. Geogrids are one of the geosynthetic subgroups whose raw materials are derivatives of oil and besides improving ability,they are used for lightweighting and economicization of the projects. The use of geogrid during recent years for improving the embankments has been done in experimental and numerical studies. Due to the increasing progress of science in the field of high speed trains for the transportation of urban and suburban passengers, it is necessary to examine the stability of the embankments. In the first in present thesis, the work that done in the laboratory was modeled in Abaqus software and the results were compared with available reported results of laboratory work in the sources and then the effect of different parameters such as the number and optimized spacing of the geogrid layers, the effect of frequency and harmonic loading amplitude and changes in the elastic modulus of geogrids have been studied on the safety factor and settlement. According to numerical studies, it has been concluded that increasing the saftey factor of embankment stability by decreasing the loading amplitude and increasing the frequency and increasing the elastic modulus of the geogrid occurs. In connection with settlement during the harmonic loading, the load amplitude has direct impact on the results, while the settlement changes are not significant compared to the loading frequency changes and the geogrid elastic modulus.