بررسي پايداري دراز‌ مدت مغار نيروگاه سدآزاد با استفاده از نتايج ابزار دقيق

Long-Term Stability Study of Azad Cavern Power House Using Instrumentation Data

مطالعات اوليه امكان احداث نيروگاه تلمبه ذخيره‌اي در محدوده سد آزاد انجام شده است. اين طرح شامل فضاهاي زيرزميني همچون تونل‌ها، چاه‌ها و دو سازه بزرگ مغار اصلي نيروگاه و مغار ترانسفورمر مي‌باشد. به سبب عمر بهره‌برداري دراز‌مدت براي سازه‌هاي موجود و همچنين وجود تجهيزات توليد برق در مغار نيروگاه، ضرورت تحليل پايداري دراز‌مدت اين سازه از اهميت بالايي برخوردار است. در اين تحقيق جهت شناخت رفتار وابسته به زمان توده‌سنگ اطراف مغار كه شامل ماسه‌سنگ با ميان‌لايه‌هاي فيليتي است، از منحني‌هاي ابزار دقيق كه در يكي از تونل‌هاي دسترسي نصب شده‌اند، استفاده شده است. از آنجا كه امكان انجام آزمايش خزش بر روي نمونه سنگ مقاوم ساختگاه ميسر نشد، لذا بصورت پيشفرض مدل رفتاري ويسكوپلاستيك برگر براي اين واحد سنگي انتخاب شد. براي شبيه‌سازي اين رفتار، از روش عددي و نرم‌افزار Flac3D استفاده شده است. نتايج مدل عددي در تطابق خوبي با نتايج پين‌هاي همگراسنجي است كه صحت شبيه‌سازي را نشان مي‌دهد. پس از انجام صحت‌سنجي در تونل دسترسي مدل رفتاري مذكور براي بررسي رفتار وابسته به زمان مغار اصلي نيروگاه نيز تعميم داده شد و در نهايت پايداري دراز‌مدت مغار نيروگاه بر اساس تحكيمات از پيش طراحي‌شده و با استفاده از نمودارهاي ظرفيت انجام شد. نتايج تحليل پايداري نشان مي‌دهد كه سازۀ مغار نيروگاه براي يك دوره 95 ساله با ضريب ايمني 1 پايدار خواهد بود.

Summary Feasibility studies of pumped storage power plant in Azad dam has been carried out. This project includes underground spaces such as tunnels, shafts and two big caverns including power house and transformer. Thus, in this research, long term stability of the support system of Azad dam is studied numerically. To determine the time-dependent behavior of the surrounding rock mass of the cavern comprising of sandstone layers with phyllite interlayers, instrument curves have been used. To simulate the cavern time-dependent behavior, numerical modeling by employing Flac3D software has been used. Long term stability analysis for 100 years was reviewed. Data which obtained from convergent pins of access tunnel was used for conformity to numerical results. The results of the time-dependent analysis show that the cavern will be stable for a 95-year period with a safety factor of 1. In general, the results of the numerical modeling indicate a good agreement with the results of convergent pins of the access tunnel. Introduction In this research, due to importance of the subject and the sufficient knowledge of conducted studies in similar cases, the long-term behavior of the main cavern in Azad dam pumped storage has been investigated. Hence, identification and description of time-dependent behavior of the surrounding rock mass is important, as it is possible to calculate and analyze time dependent deformation and, consequently, long term stability of the cavern. To understand such behavior, creep parameters should be calculated by creep tests or using instrument curves obtained from the installed convergent pins in the underground space. Finally, considering the time-dependent analysis, the stability of the cavern for different time periods can be examined. Methodology and Approaches In this study, time-dependent behavior of the surrounding cavern rocks including sandstone with interlayer phyllite, have been studied using the data from the instrumentation installed in one of the access tunnels. Viscoplastic model (CVISC) was selected for the rock mass periphery of the cavern. To simulate the CVISC model, the finite difference software (FLAC3D-V5.01) has been used. The results of the numerical method were verified with the instrumentation data. Moreover, the capacity diagrams of the support system were drawn. Results and Conclusions The results of the numerical model are in good agreement with the results of convergence pins data implying the accuracy of the numerical model. According to the long term stability analysis, the powerhouse cavern structure will be stable for a period of 95 years with safety factor of 1.