مدل‌سازي عددي تفاضل محدود نفوذ مخروط در خاك چسبنده

Numerical Modeling of Cone Penetration Test

چكيده- در اين پژوهش، آناليز تفاضل محدود تغيير شكل‌هاي بزرگ براي آزمايش نفوذ مخروط (CPT) در خاك‌هاي چسبنده، با استفاده از نرم‌افزار FLAC 2D انجام مي‌شود. در اين مدل‌سازي، المان سطح مشترك بين نفوذسنج و خاك در نظر گرفته شده و مصالح نفوذسنج به گونه اي فرض مي‌شود كه در برابر مصالح خاك، رفتاري صلب داشته باشد. رفتار خاك از مدل الاستيك-پلاستيك كامل و معيار موهر-كولمب تبعيت مي‌كند. پارامترهاي مقاومت نوك و مقاومت اصطكاكي از محاسبات نرم‌افزار به دست آمده و سپس با نتايج آزمايش صحرايي نفوذسنج مخروطي ]از سايت پروژه كارخانه ذوب آلومينيم در شهر لامرد واقع در استان فارس[، مقايسه مي شود. نتايج مدل‌سازي عددي، تطابق خوبي با نتايج آزمايش صحرايي نشان مي دهد. همچنين مش بهينه، حالت نفوذ دايم، ارزيابي نتايج با نمودار رابرتسون (1986) و نمودار اسلامي و فلنيوس (1997) هم بررسي مي‌شود

Determining the bearing capacity of piles is an important issue that always Geotechnical engineers focus on. Effect of factors such as environmental dissonance of soil which contains a pile, pile implementation, pile gender and its shape make correct estimation of bearing capacity difficult. Pile load testing as a reliable method could be used in various stages of analysis, design and implementation of piles to determine the axial bearing capacity of piles. On the other hand, pile load testing, despite high accuracy, imposes high cost and long duration for development projects and it causes limitations in this experiment. Thus acceptance of numerical analysis at geotechnical studies is increasing. In this study serious models of multi-layer perception neural network, one of the most commonly used neural networks, was used. In all models four parameters are used as input data which are length and diameter of the pile, the coefficient of elasticity and internal friction angle of soil and the bearing capacity of piles is used as output data. Models have reasonable success in predicting the bearing capacity of piles. To increase the accuracy of predicting bearing capacity, for the network training stage the real tests that has been done at the geotechnical studies of dry dock area Hormozgan by POR Consulting Engineers were used. According to (Because we) need of more data for training and testing network, several tests on pile bearing capacity, in smaller dimensions were performed in the laboratory. To perform these tests the device of pile bearing capacity, made in university of Tarbiat Modarres, was used. Models based on neural networks, unlike traditional models of behavior don’t explain effect of input parameters on output parameters. In this study, by the sensitivity analysis on the optimal structure of introduced models in each stage it has been somewhat trying to answer this question.