بررسي تعيين ظرفيت باربري جداره‌ي شمع‌هاي درجاي مستقر در سنگ

Investigation of Empirical Methods for Determining Bearing Capacity of Rock-Socketed Piles

شمع‌هاي مستقر در سنگ، به دليل توان باربري بالا و نشست‌پذيري كم، بهترين گزينه براي شالوده‌ي سازه‌هاي بسيار سنگين و حساس به نشست هستند. در اين راستا، پايگاه اطلاعاتي شامل 63 مورد آزمايش بارگذاري اجراشده روي شمع‌هاي مستقر در سنگ‌هاي با مقاومت فشاري مشخص (qu) تشكيل شد. در اين نوشتار، ابتدا روابط پژوهشگران مختلف در مورد تعيين ظرفيت باربري جدار با نتايج آزمايش‌هاي بارگذاري به تفكيك براي هر سنگ باربر توسط يك كار آماري مورد مقايسه و بررسي قرار گرفته است. سپس روابط پيشنهادي به شكل مجزا براي هر نوع سنگ و همچنين براي حالتي كه نوع سنگ مشخص نبوده و يا خارج از شمول انواع مورد بررسي در اين پژوهش است، يك رابطه‌ي كلي جهت تعيين ظرفيت باربري جدار ارايه شده است. در پايان نيز جهت لحاظ‌ اثرات مشخصات توده‌ي سنگ، ضريب اصلاحي براي مقاومت فشاري براساس RMR پيشنهاد‌ي و توسط 5 مورد عملي، دقت روابط ارايه‌شده مورد بررسي قرار گرفته است.

Rock-socketed piles can be realized as a suitable solution for the foundation systems of very heavy structures. Due to low settlement and high bearing capacities, these types of substructure are very efficient. The studies conducted by some researchers on the determination of the bearing capacity of shafts for rock-socketed piles, have been focused on parameters such as the compressive strength of rock (qu or ?c), roughness of pile-rock interface and discontinuity in the rock mass. In this study, the compressive strength parameter was applied in order to examine the bearing capacity of rock-socketed piles, since this is much easier to be specified in comparison with others. A database has been compiled consisting of 63 full scale loading tests applied to rock-socketed piles with unconfined compressive strengths of the surrounding rock. The load bearing rocks include: limestone, mudstone, siltstone, shale and granite, with compressive strengths ranging from 1.1 to 54 (MPa). The embedment length and diameters of the RSP (rock-socketed piles) vary from 0.5 to 6 and 0.5 to 1.6 meters, respectively. The empirical equations suggested by various researchers were investigated and then compared with the results of the loading tests. For each bearing rock, an exponential equation from the loading test results has been fitted using a statistical approach. Then, the equations have been proposed for each individual type of rock. Also, a general equation was suggested for the determination of the bearing capacity of the shaft for rock-socketed piles, wherein the rock type is unknown or not among those discussed in this research. Finally, in order to consider the effects of the rock mass properties, a correction factor was proposed for the compressive strength, based on RMR (Rock Mass Rating), in which, the accuracy of such a factor was discussed using five case studies.