نشریه مهندسی عمران امیرکبیر

نشریه مهندسی عمران امیرکبیر

اثر چرخه انجماد - ذوب بر چقرمگی شکست و پارامترهای مقاومتی سنگ تراورتن

نوع مقاله : مقاله پژوهشی

نویسندگان
دانشکده فنی و مهندسی، دانشگاه بین‌المللی امام خمینی (ره)، قزوین، ایران
چکیده
در ﺣﺎل ﺣﺎﺿﺮ، ﺑﺎ ﺗﻮﺳﻌﻪ ﻣﺪاوم اﻗﺘﺼﺎد در ﻣﻨﺎﻃﻖ ﺳﺮدﺳﯿﺮ در ﺳﺮاﺳﺮ ﺟﻬﺎن، ﺑﺴﯿﺎری از ﭘﺮوژهﻫﺎی ﺳﻨﮕﯽ از ﻗﺒﯿﻞ اﺳﺘﺨﺮاج ﻣﻌﺎدن و اﮐﺘﺸـﺎف  ﻧﻔـﺖ و ﮔـﺎز در این ﻣﻨﺎﻃﻖ در ﺣﺎل اﺟﺮا اﺳﺖ. در اﺳﺘﺎن‌ﻫﺎی ﺷﻤﺎل ﻏﺮب و ﻏﺮب اﯾﺮان ﮐﻪ دارای ﺗﺎﺑﺴﺘﺎنﻫﺎی ﻣﻌﺘﺪل و زﻣﺴﺘﺎن‌ﻫﺎی ﺳﺮد می‌‌باشند، ﺑﺎرﻧـﺪﮔﯽ زﯾـﺎد و ﺑـﺮودت ﻫـﻮا از ﻣﺸﺨﺼﺎت زﻣﺴﺘﺎن‌ﻫﺎی اﯾﻦ ﻣﻨﺎﻃﻖ ﺑﻪ ﺷﻤﺎر ﻣﯽ‌آﯾﺪ. در اﯾﻦ ﺷﺮاﯾﻂ ﺳﻨﮓ ﺗﺤﺖ ﺗﺄﺛﯿﺮ ﯾﺨﺒﻨﺪان‌ﻫﺎی ﻃﻮﻻﻧﯽ و چرخه­های ﻣﺘﻌﺪد ﯾﺨﺒﻨﺪان - ذوب ﻗﺮار می‌گیرد. ﺑﻨﺎﺑﺮاﯾﻦ در ﻣﻨﺎﻃﻘﯽ ﮐﻪ اﺣﺘﻤﺎل رخ دادن اﯾﻦ ﻓﺮآﯾﻨﺪ اﺳﺖ ﺿﺮوری اﺳﺖ ﺗﺎ ﺗﺄﺛﯿﺮ چرخه­ های ﻣﺘﻌﺪد ﯾﺨﺒﻨﺪان - ذوب ﺑﺮ روی وﯾﮋﮔﯽﻫﺎی ﻓﯿﺰﯾﮑﯽ و ﻣﮑﺎﻧﯿﮑﯽ ﻣﺼﺎﻟﺢ در ﻧﻈﺮ ﮔﺮﻓﺘﻪ ﺷﻮد. در این پژوهش به بررسی تاثیر فرآیند یخبندان- ذوب روی چقرمگی شکست مود Ι و Π و پارامترهای مقاومتی سنگ تراورتن پرداخته شده است. بدین منظور، برای بررسی اثر چرخه­های یخبندان- ذوب بر چقرمگی شکست مود Ι و Π، نمونه‌ها تحت 0، 1، 4، 8، 16، 32 و 64 چرخه­ یخبندان- ذوب قرار گرفته، و چقرمگی شکست مود Ι و Π در چرخه‌های ﻣﺨﺘﻠﻒ ﺑﺮرﺳﯽ ﺷﺪه اﺳﺖ. برای بررسی اثر یخبندان- ذوب روی پارامترهای مقاومتی سنگ تراورتن، نمونه‌ها تحت فشار محصور کننده 0،  2/5 و 5 مگاپاسکال قرار گرفته‌اند. همچنین برای بررسی و ارزیابی دقیق­تر تغییرات ساختاری نمونه‌ها در اثر اعمال چرخه­ های یخبندان- ذوب مطالعات میکروسکوپی نیز انجام گرفت. نتایج نشان می‌دهد که با افزایش تعداد چرخه ­های یخبندان- ذوب چقرمگی شکست مود Ι و Π به صورت نمایی کاهش می‌یابد. چقرمگی شکست مود I تراورتن سفید و قهوه ­ای بعد از 64 سیکل نسبت به سیکل صفر به ترتیب 35/48 و 37 درصد و چقرمگی شکست مود II تراورتن سفید و قهوه­ای بعد از 64 سیکل نسبت به سیکل صفر به ترتیب 45/75 و 50 درصد کاهش یافت. مقاومت فشاری سه محوری، مقاومت فشاری تک محوری، چسبندگی و زاویه اصطکاک داخلی با افزایش تعداد سیکل یخبندان- ذوب نسبت به سیکل صفر  نیز کاهش می‌باید. مطالعات میکروسکوپی نشان می‌دهد، میکروترک‌های موجود در سنگ در اثر چرخه­های یخبندان- ذوب گسترش یافته و ترک‌های جدید به وجود آمده است.
کلیدواژه‌ها

موضوعات


عنوان مقاله English

Effect of Freeze-Thaw Cycles on Fracture Toughness and Strength Parameters of Travertine

نویسندگان English

Fardin Nezamivan Chegini
Mehdi Hosseini
Imam Khomeini international university
چکیده English

The present research investigates the effect of freeze-thaw cycles on mode I and mode II fracture toughness and strength parameters of travertine. In order to investigate the effect of freeze-thaw cycles on mode I and mode II fracture toughness, the samples were exposed to 0, 1, 4, 8, 16 and 32 freeze-thaw cycles and mode I and mode II fracture toughness were studied in different cycles. Confining pressures of 0, 2.5 and 5 MPa were applied to the samples to explore the effect of freeze-thaw cycles on strength parameters of travertine. Furthermore, microscopic studies were conducted to more precisely examine and evaluate the structural changes of the samples due to freeze-thaw cycles. Results show that mode I and mode II fracture toughness decrease exponentially as the number of freeze-thaw cycles increases. Mode I fracture toughness of the white and brown travertine were decreased after 64 cycles compared to 0 cycle as much as 35.48 and 37 percent, respectively and mode II fracture toughness of the white and brown travertine were decreased after 64 cycles compared to 0 cycle as much as 45.75 and 50 percent, respectively. Moreover, as the number of freeze-thaw cycles increases, triaxial compressive strength, uniaxial compressive strength, cohesion and internal friction angle decrease with regard to 0 cycle. Microscopic studies revealed that due to the freeze-thaw cycles, the microcracks of the stones propagate and new cracks are developed.

کلیدواژه‌ها English

Freeze-thaw cycle
Fracture toughness
Strength parameters
Travertine
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