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پیشنهاد معیار گسیختگی ژئوتکنیکی ریزشمعهای خودحفار بر اساس نتایج آزمایشهای بارگذاری استاتیکی تمام مقیاس | ||
| نشریه مهندسی عمران امیرکبیر | ||
| مقاله 13، دوره 52، شماره 4، تیر 1399، صفحه 919-934 اصل مقاله (2.8 M) | ||
| نوع مقاله: مقاله پژوهشی | ||
| شناسه دیجیتال (DOI): 10.22060/ceej.2018.15093.5827 | ||
| نویسندگان | ||
| محمدعلی فخارنیا1؛ حامد بایسته* 2 | ||
| 1گروه مهندسی عمران، دانشگاه قم، قم، ایران | ||
| 2مهندسی عمران، دانشگاه قم | ||
| چکیده | ||
| دردهه اخیر استفاده از ریزشمعهای خودحفار افزایش چشمگیری داشته است. این ریزشمعها باتوجه به روش اجرا، زمان و هزینه را کاهش داده و علاوه بر تسلیح خاک، همزمان سبب بهسازی خاک نیز میگردند. باوجود افزایش استفاده از این ریزشمعها، مطالعات اندکی درخصوص عملکرد آنها خصوصا تعیین ظرفیت باربری، تدوین معیارهای گسیختگی و تفسیر آزمونهای بارگذاری صورت گرفته است. در این تحقیق 22 ریزشمع خودحفار با روش تزریق همزمان در طول ها و خاک های متفاوت اجرا و آزمونهای بارگذاری کششی و فشاری تمام مقیاس بر روی آنها انجام شده است. سپس با استفاده از شش معیار گسیختگی متداول در ارزیابی باربری شالوده های عمیق، به تشریح عملکرد و ظرفیت باربری این نوع ریزشمعها پرداخته شدهاست. درادامه با استفاده از روابط ریاضی و فرضیات موجود در خصوص منحنیهای بارگذاری- جابجایی و همچنین با استفاده از مدلسازی عددی منحنی های بار-نشست، نتایج آزمایش میدانی تا حد گسیختگی ژئوتکنیکی توسعه داده شده است. نتایج نشان میدهد از آنجا که قطر و مقاومت باند حاصل در ریزشمع های خودحفار بیش از فرضیات تئوری میباشد، معیارهای گسیختگی موجود برای تفسیر نتایج بارگذاری ریزشمعهای خودحفار مناسب نبوده و افزایش مقاومت جداره و کاهش طول الاستیک را درنظر نمیگیرند. براین اساس با استفاده از اطلاعات به دست آمده از اعمال معیارهای گسیختگی، توسعه نتایج آزمایشهای بارگذاری و بررسی اثر کوتاه شدگی الاستیک در آزمون بارگذاری، رابطهای جهت تعیین بارگسیختگی ریزشمعهای خودحفار مبتنی بر روش متعارف دیویسون ارائه شده است. | ||
| کلیدواژهها | ||
| ریزشمع خودحفار؛ بارگذاری استاتیکی؛ معیار گسیختگی؛ تمام مقیاس | ||
| موضوعات | ||
| بهسازی خاک ها؛ پی های عمیق و ریز شمع ها | ||
| عنوان مقاله [English] | ||
| A New Failure Criteria for Hollow-bar Micropile Based on Full-Scale Static Load Tests | ||
| نویسندگان [English] | ||
| Mohammadali Fakharnia1؛ hamed bayesteh2 | ||
| 1Department of civil engineering, University of Qom, Qom, Iran | ||
| 2Department of civil engineering, university of Qom | ||
| چکیده [English] | ||
| Recently, the use of hollow-bar micropiles has increased rapidly. These micropiles reduce the time and cost and not only were used as a reinforcement element but also used to improve the surrounding soils. Despite the increasing use, few studies have been conducted on the performance of this type of micropiles, in particular the determination of load capacity, failure criteria, and interpretation of loading tests. In this study, 22 hollow bar micropiles with simultaneous injection methods in different lengths and soils were executed and full-scale tension and compression loading tests were performed on them. Then, by using the six common failure criteria for pile foundation, the performance and ultimate load of these tests were evaluated. Using mathematical relations, assumptions about load-displacement curves and using numerical modeling of the observed load-displacement behavior, field test results have been developed to reach the geotechnical failure. The results show that since the diameter and bond strength of hollow bar micropiles is more than theoretical ones, the existing failure criteria are not suitable for interpretation of their load-deformation behavior. The existing failure criteria do not take into account the increase in the bond strength and the reduction of the elastic length. Based on the information obtained from the existing failure criteria and considering the effect of elastic shortening on the loading test results, a failure criterion has been proposed to determine the failure load of hollow bar micropile based on the Davison method. | ||
| کلیدواژهها [English] | ||
| Hollow bar micropile, Static load test, Failure criteria, Full scale | ||
| مراجع | ||
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