تأثیر عملی افزایش تراکم بستر ساختگاه ناشی از کوبش شمع بر کاهش استعداد روان‏گرایی آن

منصوری کیا, محمد تقی; شیبانی, حمید رضا; رجبی, الهام

doi:10.22075/jtie.2025.36354.1709

تأثیر عملی افزایش تراکم بستر ساختگاه ناشی از کوبش شمع بر کاهش استعداد روان‏گرایی آن

نوع مقاله : مقاله پژوهشی

نویسندگان

¹ دانشجوی دکتری، دانشکده فنی و مهندسی، دانشگاه پیام نور، تهران، ایران و مدیر طرحهای توسعه سد و نیروگاه، سازمان آب و برق خوزستان، ایران.

² استادیار، دانشکده فنی و مهندسی، دانشگاه پیام نور، تهران، ایران.

10.22075/jtie.2025.36354.1709

چکیده

در این تحقیق، از یک روش بر مبنای عدد SPT جهت ارزیابی استعداد روان‏گرایی لایههای ماسهای محل ساختگاه پروژه سد و قفل کشتیرانی مارد خرمشهر برای حمل و نقل رودخانهای استفاده شده است. برای ارزیابی استعداد روان‏گرایی بخش ریزدانه، روش دیگری بهکار رفته است. برای زلزلههای سطح 1 و سطح 2 (با دورههای بازگشت 75 و 475 سال)، حد مجاز برای ضریب اطمینان در برابر روان‏گرایی بهترتیب برابر 5/1 و 1/1 فرض شده است. تعداد ضربات منجر به کوبش هر یک متر از طول تمام شمعها در ساختگاه محاسبه شده است. تراکم بهوجود آمده ناشی از کوبش شمعهای سری اول معمولاً سبب افزایش تعداد ضربات لازم برای کوبش شمعهای سری دوم شده است. نسبت افزایش تعداد ضربات لازم برای کوبش شمعها در دو حالت شمعهای سری دوم نسبت به سری اول برابر نسبت افزایش عدد SPT فرض گردیده است. سپس، محاسبات تعیین ضریب اطمینان در برابر روان‏گرایی مجدداً با اعداد جدید SPT انجام شده است. بهکارگیری روش مورد اشاره، کاهش سطوح و عمقهای مستعد روان‏گرایی ناشی از تراکم لایهها پس از کوبش شمعها را نشان می‏دهد. در ساختگاه سد و قفل کشتیرانی مارد، افزایش نسبی عدد SPT نزدیک به 20 درصد بوده است. لذا روش پیشنهادی سبب کاهش 8 درصدی محدودههای مستعد روان‏گرایی شده است. ضمناً، در محدودههایی که در مطالعات فاقد استعداد روان‏گرایی تشخیص داده ولی ضریب اطمینان کمی داشتهاند نیز افزایش تقریباً 5/9 درصدی ضریب اطمینان در برابر روان‏گرایی رخ داده است. روش پیشنهادی با افزایش نسبی عدد SPT می‏تواند منجر به افزایش دقت محاسبات روان‏گرایی در ساختگاهها گردد.

کلیدواژه‌ها

موضوعات

ابنیه فنی

عنوان مقاله [English]

Practical Effect of Increasing the Density of Construction Site Due to Pile Driving on Reducing Its Liquefaction Potential

نویسندگان [English]

Mohammad Taghi Mansouri Kia ¹
Hamid Reza Sheibani ²
Elham Rajabi ²

¹ PhD student, Department of Technology and Engineering, Payame Noor University, Tehran, Iran and Manager of Dam and Power Plant Development Projects, K.W.P.A, Iran.

² Assistant Professor, Department of Technology and Engineering, Payame Noor University, Tehran, Iran.

چکیده [English]

In this research, One method, based on the SPT test number, was used to evaluate liquefaction potential of the sand layers for river navigation at the Khorramshahr dam and shipping lock construction site. For fine-grained layers, another method have been used. For level 1 and level 2 earthquakes (with return periods of 75 and 475 years), the limit to ensure against the risk of liquefaction is assumed to be 1.5 and 1.1. For each pile, the number of blows to penetrate each meter of their length is calculated. Normaly, the compression caused by striking the first series of piles has increased the number of blows required to penetrate the second series of piles. The ratio of the increase in the number of blows necessary to penetrate each pile of the second series relative to the first series has been calculated. The obtained increase rate is assumed to be equal to the increase of SPT number. Calculations to determine the safety factor against liquefaction have been done again with new SPT numbers. Application of the proposed method shows reduction of the levels and depths of liquefaction caused by the density of layers due to penetration of the piles. In the example case (Mard dam and its ship), the relative increase of SPT number was nearly 20 percent. Therefore, the proposed method has reduced the liquefaction zones by 8%. In addition, in the areas that have been diagnosed as low liquefaction potential in the studies, but had a low confidence factor, a 9.5% increase in the confidence factor against liquefaction has also occurred. By increasing the SPT number, the proposed method can increase the accuracy of liquefaction calculations in the sites.

کلیدواژه‌ها [English]

Reducing of liquefaction
soil improvement
prefabricated piles

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