ارزيابي ظرفيت باربري شمع هاي بتني درجا در ماسه با كمك نتايج آزمايش بارگذاري

Evaluation of Cast-in-Place Concrete Piles Capacity by Compressive Pile Load Testing in Sand

دقيق ترين روش تعيين ظرفيت باربري شمع ها، استفاده از آزمايش بارگذاري است. روش هاي متعددي جهت تفسير نتايج آزمايش بارگذاري شمع ها و تخمين ظرفيت باربري آنها وجود دارد. در اين مطالعه، ابتدا 12 عدد شمع با قطر متفاوت و در 4 دسته با مقياس آزمايشگاهي در سايتي متشكل از خاك ماسه‌يي واقع در حاشيه‌ي جنوبي درياي خزر اجرا و آزمايش بارگذاري بر روي آنها انجام شد. سپس با استفاده از منحني بار - نشست حاصل از آزمايش و روش هاي تجربي موجود، ظرفيت باربري شمع ها تخمين زده شد و نتايج اين روش ها با يكديگر مقايسه شد. نتايج نشان مي دهد كه روش Chin اعداد ظرفيت باربري را به مراتب بيشتر از ميانگين نتايج در اين تحقيق به‌دست مي دهد، از طرفي ديگر روش Davisson جهت تعيين ظرفيت باربري نهايي، كمترين مقادير را در اختيار قرار داده است. روش Terzaghi اعداد منطقي تري را در اين مطالعه نشان داده است. در نهايت با كمك آزمايش هاي بارگذاري انجام‌شده، نتايج قابل اطميناني از شمع ها به‌دست آمده است كه مي تواند مورد استفاده‌ي پژوهشگران قرار گيرد.

Over time, types of piles and pile installation methods have been considerably developed, and, therefore, engineers have various choices in this regard. So far, some research has been done to analyze and design cast-in-place concrete piles in sandy soil. The methods used to evaluate pile behavior are reliable only when the appropriate results have been observed in the field of numerous data. There are many ways to determine pile bearing capacity, and statistical analysis based on soil strength, the empirical method with in-situ tests results, and pile load tests are some of them. Pile load testing is an exact method to determine pile bearing capacity and is usually used in important projects. Therefore, in the present study, 12 cast-in-place concrete piles with different sizes were loaded in sand and the settlements were measured, in order to determine the ultimate bearing capacity of the piles. Piles were constructed in lab scale and were divided into 4 classes. In this article, first, some past research is reviewed. Then, soil properties and tests used for field investigation are provided. Pile installation methods and equipment used for pile testing in this study are explained. Finally, the bearing capacity of the piles is evaluated. Estimation of pile capacity based on a load-settlement curve is often difficult. There are many ways to explain test results and estimation of the bearing capacity of the piles. Then, in this study using load-settlement diagrams, the ultimate bearing capacity of the piles was estimated by existing empirical methods and the results were compared with each either. The results show that the bearing capacity in Chinʹs method is considerably higher than the average value obtained from other methods. On the other hand, Davisson’s method shows a lower value, and Terzaghiʹs method is more reliable in this study. Finally, using the pile load test, reliable results for the piles are obtained.