پیش‌بینی تنش همرسی ترک در نمونه‌های شبه سنگی دارای درزه‌های ناممتد تحت بار برش مستقیم با استفاده از روش‌های یادگیری ماشین

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه معدن، دانشکده مهندسی، دانشگاه صنعتی همدان، همدان، ایران

2 دانشکده مهندسی معدن، پردیس دانشکده‌های فنی، دانشگاه تهران، تهران، ایران

3 گروه معدن، دانشکده مهندسی، دانشگاه تربیت مدرس، تهران، ایران

چکیده

شکستگی‌ها معمولاً به شکل درزه‌ها و ریزترک‌ها در توده سنگ‌ یافت می‌شوند و مکانیسم شکست آن‌ها به‌شدت به الگوی همرسی ترک بین ناپیوستگی‌های از قبل موجود بستگی دارد. تعیین رفتار شکست درزه‌های ناممتد یک مسئله مهندسی است که پارامترهای مختلفی ازجمله خصوصیات مکانیکی توده سنگ، تنش نرمال و نسبت سطح درزه به سطح برشی کل (ضریب درزه‌داری) را شامل می‌شود. در این مقاله، به‌منظور پیش‌بینی تنش همرسی ترک از دو روش یادگیری ماشین شامل الگوریتم بهینه‌ساز گرگ خاکستری (GWO) و برنامه‌ریزی بیان ژن (GEP) استفاده شده است. بدین منظور 8 پارامتر ورودی مؤثر بر تنش همرسی ترک ازجمله ضریب درزه‌داری (JC)، تنش نرمال (σn)، مقاومت فشاری تک‌محوره (σc)، مقاومت کششی (σt)، نسبت پواسون (υ)، مدول الاستیسیته (E)، مقاومت چسبندگی (C) و زاویه اصطکاک داخلی (φ) بر اساس نتایج 450 آزمایش برش مستقیم انجام‌شده بر روی نمونه‌های شامل 2 دسته‌درزه ناممتد ساخته‌شده از ترکیب گچ، سیمان و آب انتخاب و سپس روش‌های GWO و GEP پیاده‌سازی گردیدند. به‌منظور ارزیابی کارایی مدل‌ها در پیش‌بینی تنش همرسی ترک‌ در نمونه‌ها، از 3 شاخص ضریب تعیین (R2)، جذر میانگین مربعات خطا (RMSE) و میانگین خطای مطلق (MAE) برای داده‌های آموزش و تست استفاده شد. مقادیر ضریب تعیین روش‌های GWO و GEP برای داده‌های آموزش به ترتیب 962/0 و 938/0 و برای داده‌های تست به ترتیب 996/0 و 981/0 به دست آمد که نشان‌دهنده کارایی بالاتر روش GWO در مقایسه با GEP است. به‌علاوه، نتایج نشان داد که مقادیر شاخص‌های RMSE و MAE در هر دو مرحله آموزش و تست برای الگوریتم GWO کمتر از روش GEP می‌باشند که بیانگر خطای کمتر الگوریتم GWO و قابلیت اطمینان و دقت بالاتر آن نسبت به روش GEP است. بااین‌حال، می‌توان گفت که دو روش مورداستفاده دارای دقت بالایی بوده و بر اساس روش GEP رابطه‌ای جهت پیش‌بینی تنش همرسی ترک ارائه شد. همچنین، نتایج آنالیز اهمیت نشان می‌دهد که از بین پارامترهای ورودی، تنش نرمال (σn) و ضریب درزه‌داری (JC) به ترتیب بیشترین و کمترین تأثیر را بر تنش همرسی ترک دارند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Prediction of crack coalescence stress in rock-like specimens with non-persistent joints under direct shear test based upon machine learning algorithms

نویسندگان [English]

  • Vahab Sarfarazi 1
  • Fariborz Matinpoor 2
  • Shadman Mohamadi Bolban Abad 3
  • Masoud Monjezi 3
1 Dept. of Mining, Faculty of Engineering, Hamedan University of Technology, Hamedan, Iran
2 Dept. of Mining Engineering, Technical Faculties Campus, University of Tehran, Tehran, Iran
3 Dept. of Mining, Faculty of Engineering, Tarbiat Modares University, Tehran, Iran
چکیده [English]

Concretes frequently contain joints and microcrack fractures, and the failure mechanism of these fractures is highly dependent on the pattern of crack coalescence between pre-existing flaws. Determining the non-persistent joints' failure behavior is an engineering challenge that incorporates several factors, including the ratio of the joint surface to the total shear surface, normal stress, and the mechanical characteristics of the concrete. This paper aims to utilize grey wolf optimizer (GWO) and gene expression programming (GEP) algorithms for the prediction of the crack coalescence stress (CCS). For this purpose, 8 input parameters affecting the CCS including jointing coefficient (JC), normal stress (σn), uniaxial compressive strength (σc), tensile strength (σt), Poisson's ratio (υ), modulus of elasticity (E), cohesion strength (C) and internal friction angle (φ) were selected based on the results of 450 direct shear tests conducted on specimens including 2 sets of non-persistent joints made of gypsum, cement, and water. The GWO and GEP techniques were then implemented. Three performance indicators of determination coefficient (R2), root mean square error (RMSE), and mean absolute error (MAE), were employed for the training and testing phases to evaluate the efficiency of the suggested models. The R2 values for GWO and GEP for the training phase were 0.962 and 0.938, respectively, while for the testing phase were 0.996 and 0.981, indicating that the GWO algorithm is more efficient than GEP. Moreover, the findings reveal that the GWO algorithm exhibits lower RMSE and MAE values in both the training and testing phases compared to the GEP method. However, it can be professed that the two methods used have high reliability and accuracy. Also, based on the GEP method, a formula was derived and presented for prediction of CCS. At last, according to the sensitivity analysis, it was found that the normal stress (σn) and jointing coefficient (Cu) have the greatest and least influence on CCS, respectively...

کلیدواژه‌ها [English]

  • Non-persistent joint
  • Rock bridge
  • Crack coalescence stress
  • Grey wolf optimizer (GWO)
  • Gene expression programming (GEP)
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