بررسي تاثير اسلامپ بتن در ظرفيت باربري فشاري ريزشمع بتني درجا (مطالعه‌ي موردي ساختگاه سرخرود)

A Survey of Concrete Slump Effects on the Compressive Capacity of Drilled Shafts (Case study: Sorkhrood Site)

در مناطقي با خاك هاي سطحي كه ويژگي هاي مكانيكي ضعيفي دارند، استفاده از پي هاي عميق يكي از راه حل هاست. در اين صورت، پي هاي عميق توانايي حمل نيروهاي وارده را دارند. در اين راستا، پژوهشگران با انجام پژوهش هاي آزمايشگاهي به بررسي پارامترهاي گوناگون تاثيرگذار در رفتار ريزشمع پرداخته اند. در اين نوشتار، ظرفيت باربري ريزشمع هاي منفرد درجاي بتني با بررسي تاثير اسلامپ هاي متفاوت در خاك ماسه‌يي بد دانه بندي‌شده‌ي منطقه‌ي سرخرود مورد بررسي قرار گرفته است. آزمايش هاي ظرفيت باربري ريزشمع بر روي 15 نمونه‌ي ريزشمع به طول 150 و قطر 12 سانتي‌متر انجام شده است. بتن ريزشمع ها در 5 گروه متفاوت با مقاومت فشاري 210 كيلوگرم بر سانتي‌متر مربع بوده است. طبق مشاهده‌هاي تجربي، افزايش اسلامپ بتن تشكيل‌دهنده‌ي بدنه‌ي ريزشمع از 10 به 24 سانتي متر منجر به افزايشي در حدود 2 برابر در ظرفيت باربري ريزشمع شده است. در انتهاي نوشتار، ظرفيت باربري ريزشمع با روش هاي متداول مقايسه و مورد بحث قرار گرفته است.

Using deep foundations is a solution in regions with surface soil having poor mechanical properties. Indeed this kind of foundation can bear horizontal, gravitational and tensile forces. In this regard, researchers study effective various parameters on pile behavior in the laboratory, such as the effect of pile dimensions, soil properties, methods of installation, types of loading, and some other effective parameters. The bearing capacity of single drilled shafts with the effects of various slumps on poor gradation sandy soil is investigated in this paper, in Sorkhrood. Experiments related to the bearing capacity of a pile using 15 pile samples with 150cm length and 12cm diameter have been undertaken. The concrete used in the piles is considered as 5 discrepant groups, with constant slump of 10, 12, 16, 20 and 24cm and a compressive strength of 210 kg/cm. A strong polymer pipe has been used as a casing, drilled step by step into the ground and then taken from the ground frequently. According to the experimental observations, increasing the amount of concrete slump used in the pile body has a great influence on pile bearing capacity. It is shown that the bearing of compressive piles has been increased in the higher slumps. Increasing the amount of slump, due to the combination of the casing of the pile with the soil around the casing, changes some parameters of the soil, reducing the shaping. The amount of its influence leads to the double difference between the bearing capacity of the pile filled with the lowest slump and the pile filled with the highest slump. It is indicated that the method presented by Janbo & Bousen is an entirely conservative method, while the method presented by Mayerhouf and Bousen is closest to the results of the bearing experiments in calculating the final bearing capacity. Finally, the bearing capacity of piles is investigated and compared with common methods.