ارزيابي عددي اثر دما در مقاومت سطح مشترك با رويكرد شمع هاي حرارتي

Numerical Investigation of Temperature Effect on Interface Strength in Energy Piles

انرژي زمين‌گرمايي يكي از منابع نامحدود انرژي در سطح جهان است. يكي از راه‌هاي برداشت انرژي مذكور، استفاده از شمع‌هاي حرارتي است كه علاوه بر انتقال بار سازه‌ي بالايي، وظيفه‌ي انتقال حرارت بين زمين و ساختمان را دارند. از اين رو توده‌ي خاك و شمع متحمل بارهاي حرارتي مي‌شوند كه مي‌توانند مشخصه‌هاي مكانيكي و مقاومتي سطح مشترك خاك و شمع را تحت تأثير قرار دهند. به همين منظور، براي بررسي تأثير دما در مقاومت سطح مشترك خاك و شمع، مجموعه‌ي آزمايش‌هاي برش مستقيم به‌صورت تحليل همبسته‌ي ترموهيدرومكانيكي، براي اولين بار در نرم‌افزار المان محدود آباكوس بررسي شده است. در مدل‌سازي انجام شده، تغييرات مقاومت برشي سطح مشترك خاك رس ايليت و بتن تحت تأثير بار مكانيكي و ترمومكانيكي بررسي شده است. اصلي‌ترين نتيجه‌ي پژوهش حاضر نشان مي‌دهد كه با افزايش دما به ميزان 50 درجه‌ي سانتي‌گراد، مقاومت سطح مشترك خاك و شمع به طور متوسط به اندازه‌ي 20 كيلوپاسكال افزايش مي‌يابد.

Due to the growth of energy consumption, air pollution and global warming in the world, the use of renewable energy has become popular in the world due to its variety of resources, lower economic cost and environmental compatibility. One of the unlimited sources of renewable energy, is geothermal energy. Since geothermal energy resources are unlimited and can be exploit in many parts of the world, its application as a reliable source of energy is growing. The use of energy piles as a heat exchanger is one way to exploit this energy. These piles are being used to serve dual purposes: transfer the structural load to the ground and act as heat exchanger elements to extract and inject heat from and to the ground. Energy piles are subjected to daily and seasonal cyclic temperature changes during their life span. These temperature changes (heat cycle) induce cyclic expansion-contraction along the pile-soil interface that may affect interface properties such as shear strength. The pile-soil interface is defined as a thin zone of soil that can be subjected to different boundary conditions with respect to the surrounding soil. Therefore, in order to investigate the influences of temperature on soil-pile interface, a series of direct shear tests is modeled in ABAQUS software. In this modeling the shear strength changes of Illite clay and concrete interface, are investigated under mechanical and thermo-mechanical loading. A series of analysis are conducted with sample temperature of 50 and the normal stresses of the direct shear analysis are 50, 100 and 150 kPa. This analysis is done at a shearing rate of 0.006 mm/min. In this investigation, it is assumed that the properties of concrete materials are not temperature dependent and their behavior is thermoelastic. In this paper, the main results of modeling show that the shear strength of Illite clay-concrete interface, increases by an average of 20 kPa with increasing in temperature by 50 .