شبيه سازي عددي تأثير لوله زهكش بر نيروي بالابرنده و گراديان هيدروليكي خروجي در سدهاي وزني

Numerical Simulation of Effect of Drain Pipe in Uplift Force and Exit Hydraulic Gradient in Gravity Dams

در اﯾﻦ ﺗﺤﻘﯿﻖ ﺗﺄﺛﯿﺮ ﻗﻄﺮ و ﻣﻮﻗﻌﯿﺖ ﻟﻮﻟﻪ زﻫﮑﺶ در ﭘﯽ ﺳــﺪﻫﺎي وزﻧﯽ ﺑﺮ روي ﻧﯿﺮوي ﺑﺎﻻﺑﺮﻧﺪه و ﮔﺮادﯾﺎن ﻫﯿﺪروﻟﯿﮑﯽ ﺧﺮوﺟﯽ ﻣﻮردﺑﺮرﺳﯽ ﻗﺮار ﮔﺮﻓﺖ. ﺑﺮاي اﯾﻦ ﮐﺎر، از ﯾﮏ ﻣﺪل ﻋﺪدي ﺑﺎ روش اﻟﻤﺎنﻫﺎي ﻣﺤﺪود ا ﺳﺘﻔﺎده ﮔﺮدﯾﺪ و ﭘﯽ ﯾﮏ ﺳﺪ وزﻧﯽ ﺷﺒﯿﻪ ﺳﺎزي ﺷﺪ. ﻧﺘﺎﯾﺞ ﻧ ﺸﺎن داد ﮐﻪ وﺟﻮد ﻟﻮﻟﻪ زﻫﮑﺶ در زﯾﺮ ﺳﺪ وزﻧﯽ، ﺑﺎﻋﺚ ﮐﺎﻫﺶ ﻧﯿﺮوي ﺑﺎﻻﺑﺮﻧﺪه و ﮔﺮادﯾﺎن ﻫﯿﺪروﻟﯿﮑﯽ ﺧﺮوﺟﯽ ﻣﯽﮔﺮدد. ﻫﻤﭽﻨﯿﻦ ﺗﻌﺒﯿﻪ ﻟﻮﻟﻪ زﻫﮑﺶ در ﻓﺎ ﺻﻠﻪ ﯾﮏﭼﻬﺎرم ﻋﺮض ﮐﻒ ﺳﺪ )0/25L( و ﺳﻪﭼﻬﺎرم ﻋﺮض ﮐﻒ ﺳﺪ )0/75L( از ﭘﺎ ﺷﻨﻪ، ﺑﻪ ﺗﺮﺗﯿﺐ ﮐﻤﺘﺮﯾﻦ ﻧﯿﺮوي ﺑﺎﻻﺑﺮﻧﺪه و ﮔﺮادﯾﺎن ﻫﯿﺪروﻟﯿﮑﯽ ﺧﺮوﺟﯽ را ﺧﻮاﻫﺪ داﺷـــﺖ. ﺗﺄﺛﯿﺮ ﻋﻤﻖ ﮐﺎرﮔﺬاري ﻟﻮﻟﻪ زﻫﮑﺶ ﺑﺮ ﻧﯿﺮوي ﺑﺎﻻﺑﺮﻧﺪه ﻧﯿﺰ ﺑﺮرﺳﯽ ﮔﺮدﯾﺪ و ﻣﺸﺎﻫﺪه ﺷﺪ ﮐﻪ اﺑﺘﺪا روﻧﺪ ﮐﺎﻫﺸﯽ و ﺳﭙﺲ روﻧﺪ اﻓﺰاﯾﺸﯽ دارد. ﻫﻤﭽﻨﯿﻦ ﻣﺸـــﺨﺺ ﮔﺮدﯾﺪ ﮐﻪ اﻧﺘﺨﺎب ﻗﻄﺮ ﻟﻮﻟﻪ زﻫﮑﺶ ﺗﺨﻠﯿﻪ ﺗﺎﺑﻊ ﻣﻼﺣﻈﺎت اﺟﺮاﯾﯽ اﺳـــﺖ. ﺑﺎ ﻣ ﺸﺨﺺ ﺷﺪن ﺑﻬﺘﺮﯾﻦ ﻣﻮﻗﻌﯿﺖ ﺑﺮاي ﺗﻌﺒﯿﻪ ﻟﻮﻟﻪ زﻫﮑﺶ ﻣ ﺸﺎﻫﺪه ﮔﺮدﯾﺪ ﺿﺮﯾﺐ اﻃﻤﯿﻨﺎن ﺳﺎزه در ﻣﻘﺎﺑﻞ واژﮔﻮﻧﯽ اﻓﺰاﯾﺶ 1/5 ﺗﺎ 2 ﺑﺮاﺑﺮي دارد.

In this study, the effects of diameter and location of drain pipe in uplift force and exit hydraulic gradient in the foundation of gravity dams are investigated. For this purpose, a numerical model of gravity dam foundation is simulated using finite elements method. The results indicate that drain pipe under the gravity dam reduces the uplift force and exit hydraulic gradient. Location of the drain pipe in 0.25L (L is the dam width), and 0.75L from the dam heel, causes to reduce for uplift force and exit hydraulic gradient in minimum value, respectively (optimum place). In addition with increasing the depth of drain, the uplift force at first decreases and then increases. The drain pipes diameter has little effect in uplift force and exit hydraulic gradient and thus its selection is dependent to construction cost considerations. By defining the best position for the location of drain pipes, it was observed that drainage pipes in these situations increase the safety factor up to 1.5 to 2 times against the structural overturning.