ارزیابی ﻛﺎﻫﺶ ایمنی ﺳﺎزه ای ﻧﺎشی از ﻧﻔﻮذ آب ﻣﺨﺰن ﺑﻪ درون ﺳﻄﺢ ﺗﺮک ﺳﺎزه ای ﻳﻚ ﺳﺪ ﺑﺰرگ ﺑﺘنی ﻗﻮسی

آﺳﻴﺐ در ﺳﺪﻫﺎی ﻗﻮسی ﻛﻪ از ﺳﺎزهﻫﺎی ﺑﺴﻴﺎر ﻣﻬﻢ و ﺣﻴﺎتی ﻫﺮ ﺟﺎﻣﻌﻪای ﻣﺤﺴﻮب می ﺷﻮﻧﺪ، ﺑﻪ دﻟﻴﻞ ﺧﺴﺎرتﻫﺎی ﻓﺎﺟﻌﻪآﻣﻴﺰ ﻧﺎشی از ﺧﺮابی اﺣﺘﻤﺎلی ﺷﺎن ﺑﺎﻳﺪ ﻫﻤﻮاره ازﻧﻈﺮ ﻋﻤﻠﻜﺮدی ارزﻳﺎبی ﺷﻮﻧﺪ و ﺳﻄﺢ اﻳﻤنی آنﻫﺎ ﺑﺮای اداﻣﻪ ﺣﻴﺎت ﺳﺪ ﺑﺮرسی و ﻣﺸﺨﺺ ﺷﻮد. در اﻳﻦ ﻣﻴﺎن اﮔﺮ آﺳﻴبی ﻣﺸﺨﺺ ﻫﻤﭽﻮن ﺗﺮک ﺧﻮردگی در اﻳﻦ ﺳﺎزهﻫﺎ وﺟﻮد داﺷﺘﻪ ﺑﺎﺷﺪ، اﻳﻦ ارزﻳﺎبی ﻫﺎ ﺑﺮای ﻣﺸﺨﺺ ﺷﺪن ﺳﻄﺢ اﻳﻤﻨﻲ ﻓﻌلی و ﭘﻴﺶ ﺑﻴنی از ﻣﻘﺎوﻣﺖ رزرو ﺳﺎزه در ﺑﺮاﺑﺮ ﺑﺎرﮔﺬاریﻫﺎی ﻣﺨﺘﻠﻒ ازﺟﻤﻠﻪ زﻟﺰﻟﻪ ﺿﺮورت می ﻳﺎﺑﺪ ﻛﻪ ﻣﻮرد ﻣﺸﺎﺑﻪ آن در ﻛﺸﻮر ﻣﻮﺟﻮد اﺳﺖ. ﺳﺪ ﻣﺎروﭘﻮﻳﻨﺖ ﺑﻪ ﻋﻨﻮان ﻣﻄﺎﻟﻌﻪ ﻣﻮردی ﺑﺮای دﺳﺘﻴﺎبی ﺑﻪ ﺷﻨﺎﺧﺖ ﻻزم در ﻣﻮرد ﺗﺄﺛﻴﺮ ﺗﺮک ﺧﻮردگی ﺑﺮ ﻋﻤﻠﻜﺮد ﺳﺪ و ﻣﺸﺨﺺ ﺷﺪن ﺳﻄﺢ اﻳﻤنی آن اﻧﺘﺨﺎب ﺷﺪ و ﻫﻨﺪﺳﻪای ﻣﺸﺨﺺ از ﺗﺮک در ﺑﺪﻧﻪ ﺳﺪ اﻳﺠﺎد ﺷﺪ. ﻣﺪلﺳﺎزی ﺳﻪﺑﻌﺪی ﺳﺪ ﻫﻤﺮاه ﺑﺎ ﭘﻲ ﺑﺮای ﭼﻨﺪ دﺳﺘﻪ ﺗﺮک ﻣﺨﺘﻠﻒ ﺑﺎ ﻫﻨﺪﺳﻪ ﻣﺸﺨﺺ و ﻣﺸﺨﺼﺎت ﻣﻜﺎﻧﻴﻜﻲ ﻣﺨﺘﻠﻒ ﺳﺎﺧﺘﻪ ﺷﺪ و ﺑﺮای ﻣﺪلﺳﺎزی ﺗﺮک ﻧﻴﺰ از درز ﻓﺸﺎری-ﺑﺮﺷﻲ اﺳﺘﻔﺎده ﺷﺪ. ﺑﺎرﮔﺬاریﻫﺎی اﻋﻤﺎلﺷﺪه ﻧﻴﺰ ﺑﺎرﻫﺎی ﺳﺮوﻳﺲ (وزن و ﻓﺸﺎر آب) و ﻫﻤﭽﻨﻴﻦ ﺑﺎر ﻏﻴﺮﻋﺎدی ﻧﻔﻮذ آب در ﺗﺮک ﻫﺴﺘﻨﺪ. در دﺳﺘﻪ اول ﺗﺤﻠﻴﻞﻫﺎ ﻣﺸﺨﺼﺎت ﻣﺼﺎﻟﺢ ﺧﻄﻲ ﻓﺮض ﺷﺪﻧﺪ و ﺑﺎ ﻣﺸﺎﻫﺪه ﺗﻨﺶﻫﺎی ﻛﺸﺸﻲ ﺑﺰرگ، ﺑﺮای ﻣﻮارد ﻣﻨﺘﺨﺐ از ﻣﺼﺎﻟﺢ ﻏﻴﺮﺧﻄﻲ ﺑﺘﻦ ﺑﺎ ﺑﻪﻛﺎرﮔﻴﺮی ﻣﺪل آﺳﻴﺐ ﭘﻼﺳﺘﻴﻚ اﺳﺘﻔﺎده ﺷﺪ و ﻣﺼﺎﻟﺢ پی ﺧطی ﺑﺎقی ﻣﺎﻧﺪ. ﺿﺮاﻳﺐ اﻃﻤﻴﻨﺎن ﺑﺮشی و ﻓﺸﺎری ﺑﺮای ﺳﻄﻮح درزﻫﺎی اﻧﻘﺒﺎض و ﺻﻔﺤﻪ ﺗﺮک ﻣﺤﺎﺳﺒﻪ ﺷﺪﻧﺪ و ﺑﺮای ﺿﺮاﻳﺐ اﻃﻤﻴﻨﺎن ﺳﻄﻮح ﺑﺪﻧﻪ ﺳﺪ از ﻣﻌﻴﺎر ﮔﺴﻴﺨﺘگی ﻣﺘﻨﺎﺳﺐ ﺑﺎ ﺑﺘﻦ اﺳﺘﻔﺎده ﺷﺪه اﺳﺖ. ﻫﻤﭽﻨﻴﻦ ﺑﺮای ﺳﺎﺧﺖ ﻣﺪلﻫﺎی ﺳﻪﺑﻌﺪی ﺳﺪ، ﻣﺮاﺣﻞ ﺳﺎﺧﺖ ﺳﺪ و درزﻫﺎی اﻧﻘﺒﺎض ﺑﻴﻦ ﻃﺮهﻫﺎ ﻣﺪل ﺷﺪه اﺳﺖ. ﻧﺘﺎﻳﺞ ﺑﻪ دﺳﺖ آﻣﺪه ﻧﺸﺎﻧﮕﺮ اﻳﻦ ﻫﺴﺘﻨﺪ ﻛﻪ ﺑﺮای ﺗﺮک ﺑﺎ ﻋﻤﻖ ﻧﻔﻮذ ﻧﺼﻒ در ﺿﺨﺎﻣﺖ ﭘﻮﺳﺘﻪ، ﺑﺮای ﻫﺮدو ﺣﺎﻟﺖ ﻧﻔﻮذ و ﻋﺪم ﻧﻔﻮذ آب در ﺗﺮک، ﺿﺮاﻳﺐ اﻃﻤﻴﻨﺎن اﻓﺖ ﻣﺤﺴﻮسی ﻧﺪاﺷﺘﻨﺪ و ﻧﮕﺮانی از ﺑﺎﺑﺖ ﻋﻤﻠﻜﺮد و اﻳﻤنی ﻣﺘﻮﺟﻪ ﺳﺪ ﻧﻴﺴﺖ. اﻣﺎ ﺑﺎ اﻓﺰاﻳﺶ ﻋﻤﻖ ﻧﻔﻮذ ﺑﻪﻛﻞ ﺿﺨﺎﻣﺖ ﺳﺪ، ﺑﺮای ﺑﺎرﻫﺎی ﺳﺮوﻳﺲ ﺑﺪون ﻧﻔﻮذ آب در ﺗﺮک، ﺑﺎ ﻛﺎﻫﺶ زاوﻳﻪی اﺻﻄﻜﺎک ﺳﻄﺢ ﺗﺮک ﺧﻮرده، ﺿﺮاﻳﺐ اﻃﻤﻴﻨﺎن اﻓﺖ ﻣﺤﺴﻮسی دارﻧﺪ و در ﺻﻮرت اﻓﺰودن ﻧﻔﻮذ آب داﺧﻞ ﺗﺮکﻫﺎ، اﻳﻦ ﺑﺎرﮔﺬاری ﺑﻪﻋﻨﻮان ﻋﺎﻣلی ﺗﺸﺪﻳﺪ ﻛﻨﻨﺪه ﻋﻤﻞ ﻧﻤﻮده و ﺧﺮابی ﻫﺎی ﭘﺎی ﻃﺮه ی ﺗﺮک ﺧﻮرده را اﻓﺰاﻳﺶ می دﻫﺪ. ﻫﻤﭽﻨﻴﻦ اﺛﺮ ﺧﺮابی ﻫﺎی ﻣﺬﻛﻮر روی پی، ﺧﺒﺮ از اﻓﺖ ایمنی ﺑﺮشی در ﻣﺤﻞ اﺗﺼﺎل ﺳﺪ ﺑﻪ ﻃﺮه ی ﺗﺮک ﺧﻮرده می دهد.

evaluation of structural safety reduction due to reservoir water penetration into a major structural crack in a large concrete dam

structural damages in arch dams, are often of major concern and should inevitably be evaluated for probable rehabilitation to ensure safe regular normal operation and safe behavior in future under unusual loading. these are crucial to prevent any catastrophic or failure consequences for the life time of the dam. if there is a specific major infection such as a large crack in the dam body, the assessments will be necessary to determine the current level of safety and predict the resistance of the structure to various future loading, such as earthquakes, etc. in this research, morrowpoint dam is selected as a case study to assess the dam performance and its safety level, at the presence of an actual crack with almost known geometry created in the dam body during the sequence of its reservoir first impounding. three-dimensional modeling of the dam and its foundation is constructed for several different crack types with specific geometry and different mechanical properties. for modeling of both the existing cracks, and the vertical contraction joints of the arch dam, no-tension, zerothickness joint elements with variable compression-shear behavior are used. the applied loads include normalor service loads (weight and hydrostatic water pressure) as well as abnormal load of water penetration into thecrack surface. in the first set of analyses, concrete material is assumed as linear. by observing the high tensile stresses, non-linear concrete materials with plastic damage model is introduced for selected cases although the foundation materials remain as linear. safety factors of shear and compressive tractions are calculated at the surfaces of the contraction joints and the cracks. for the safety factor of the dam body mass concrete surfaces, a 2-d failure criterion is employed. in applying the weight load, the construction sequence of 3d blocks of the dam, and the stages of grouting the contraction joints have been fully accounted for. the results indicate that for cracking with an extension depth of half the thickness of the dam body, for both cases of penetration and non-penetration of water load into the cracks, safety factors are only slightly reduced and thus the dam safety in normal loading condition remains acceptable. however, in the case of increasing the depth of crack extension into the entire thickness of the dam body, the friction angle of the cracked surface is crucial, and if reduced, the normal loading safety factors of stresses and joints tractions are reduced significantly even whenneglecting water penetration effects in cracks. when water penetration into the cracks is added during normal loading case, the situation is of much concern and great damages are expected. simultaneously, it is observed that, the foundation interface also suffers of much shear safety loss.