تعيين مشخصات ديناميكي سد مارون با استفاده از آزمايشهاي ارتعاش محيطي و روش عددي FEM

Evaluation of Dynamic Characteristics of Marun Embankment Dam Using Ambient Vibration Test and FEM

تعيين مشخصات ديناميكي سازه‌هاي مهم از جمله سدهاي خاكي در مناطق لرزه ‌خيز جهان از اهميت ويژه اي برخوردار است. بر اين مبنا براي اولين بار در ايران آزمايش ارتعاش محيطي بر روي سد مخزني مارون صورت گرفته است و به كمك روشهاي جديد پردازش سيگنال، مشخصات ديناميكي اين سد از جمله فركانسها، اشكال و ميراييهاي مودي بدنه سد به دست آمده اند. همچنين مدلهاي اجزاي محدود اين سد با استفاده از نرم افزار رايانه اي ANSYS تهيه شده است و با بالا بردن دقت مدلسازي از نظر شرايط هندسي، مشخصات مصالح، شرايط مرزي- تكيه گاهي و نهايتا كاليبراسيون مدلFEM سد با نتايج آزمايشات ارتعاش محيطي، مدل عددي سد مارون در محدوده كرنشهاي كوچك تدقيق شده است.

There is a worldwide interest in the proper design of embankment dams to resist earthquake loadings. For the first time in Iran, a complete ambient vibration survey due to low-level loads such as wind, machinery activities, low level tectonic activities, and water exit from bottom outlet was performed on Marun embankment dam. These kinds of ambient vibration tests are suitable for manifesting the lower vibration modes of the dam body. Using different signal processing methods such as Power Spectra Density, the results of in-situ tests have been used to evaluate the natural frequencies, mode shapes and modal damping of the dam body. Besides ambient vibration tests, the 3-D modal analysis of the dam body was performed using ANSYS software. The foundation and abutment flexibility effects on dynamic characteristics of the dam body was investigated and the dynamic soil properties were used from Engineer’s report and some empirical relations. Also initial shear modulus of the dam body and foundation materials were evaluated by refraction survey. In this paper, the test procedures, related signal processing results, numerical analysis results and its comparison with the dynamic characteristics of the dam body obtained from the full-scale dynamic tests will be presented. Finally, calibrating procedures of the numerical model (based on increasing the accuracy of dam body geometry, soil and rock material parameters and foundation and abutment flexibility) will be discussed.