بررسي خواص ژيومكانيكي مصالح درشت‌دانه با درنظرگرفتن سطح تنش

Investigation of Geomechanical Properties of Coarse Aggregates Considering Stress Levels

با توجه به تاثير زياد سطح تنش در رفتار تنش-كرنش مصالح دانه‌يي درشت، تعيين پارامترهايي مانند زاويه‌ي اصطكاكي بحراني و بيشينه‌ي اين سنگ‌دانه‌ها اهميت بالايي در پروژه‌هاي عمراني دارد. در اين مطالعه، يك مجموعه از آزمون‌هاي سه محوري بزرگ‌مقياس بر روي سنگ‌دانه‌ها با سطوح تنش مختلف انجام و با تركيب اطلاعات به‌دست‌آمده با ساير داده‌هاي جمع‌آوري‌شده از آزمون‌هاي موجود در ادبيات فني، تاثير جنس، شكل و منشا دانه‌ها در پارامترهاي ژيومكانيكي اين نوع مصالح بررسي و در نهايت روابط و بازه‌ها‌يي براي به‌دست‌آوردن زاويه‌ي اصطكاك داخلي بيشينه و بحراني ارايه شده است. بر اساس نتايج حاصله با افزايش تنش همه‌جانبه در تمامي سنگ‌دانه‌ها، زاويه‌ي اصطكاك بحراني كاهش يافته است. همچنين نشان داده شده است كه در تنش‌هاي همه جانبه‌ي بالا، تاثير جنس و شكل ذرات در مقاومت آنها بسيار ناچيز است.

Coarse-grained materials are of great importance in geotechnical engineering practice. They are widely used where a high-strength material is required to support heavy loads; where cyclic loads are encountered or where the abrasive strength controls the design criteria. Unlike fine-grained materials, which are characterized by their plasticity indices or mineralogy, coarse-grained materials are most likely to be characterized by the shape, size distribution and type or origin of the grains. Model parameters in such constitutive models are defined by the material type, shape and size. Material shear strength parameters are also functions of stress level. On the one hand, physical properties, like abrasive strength and breakage ratio, are of great importance, since they are directly (as major design criteria) or indirectly (as independent parameters in constitutive models) required in the analysis and design of geo-materials. Therefore, characterization of coarse-grained material behavior based on the type, shape and size of the grains is worthy of further consideration. In this research, the relationship between particle type, shape and size and the mechanical and physical properties of coarse-grained materials has been studied. An attempt was made to correlate the stress level effect, the shear strength properties and grain type, shape and size. Also, the abrasive strength and breakage ratio (physical properties) have been studied. Furthermore, it is considered as to how these parameters could have a relationship with each other, and how the critical friction and peak friction angle could have a relationship with the variations of stress level and abrasive strength. Eventually, an experimental program was conducted and some kinds of material, with diverse characteristics in origin, shape, type and etc., were selected and tested. Finally, by gathering other results from prior research, some formulas were recommended.