كليدواژه :
آستانه و آبشكن , صفحات مستغرق , توپوگرافي بستر , آبگير و آبشستگي
چكيده فارسي :
در اﻳﻦ ﭘﮋوﻫﺶ، ﺑﻪ ﺻﻮرت آزﻣﺎﻳ ﺸﮕﺎﻫﻲ، ﺗﺎﺛﻴﺮ ﺗﺮﻛﻴﺐ ﺳﺎزهﻫﺎي ﻛﻨﺘﺮل ر ﺳﻮب از ﻗﺒﻴﻞ آ ﺳﺘﺎﻧﻪ، آﺑ ﺸﻜﻦ و ﺻﻔﺤﺎت ﻣ ﺴﺘﻐﺮق ﺑﺎ اﺑﻌﺎد ﻣﺨﺘﻠﻒ ﺑﺮ ﺗﻮﭘﻮﮔﺮاﻓﻲ ﺑﺴﺘﺮ در اﻃﺮاف آﺑﮕﻴﺮ ﺟﺎﻧﺒﻲ 90 درﺟﻪ در ﻳﻚ ﻛﺎﻧﺎل ﻣﺴﺘﻘﻴﻢ و ﻧﻴﺰ ﺑﺮ اﺑﻌﺎد ﻧﺎﺣﻴﻪ آﺑﺸﺴﺘﮕﻲ در ﭘﺎﻳﻴﻦ دﺳﺖ آﺑﮕﻴﺮ در ﻛﺎﻧﺎل ا ﺻﻠﻲ ﺑﺮر ﺳﻲ ﺷﺪه ا ﺳﺖ. ﭘﮋوﻫ ﺸﻬﺎ در ﺷﺶ ﺳﺎﻣﺎﻧﻪ ﻛﻨﺘﺮل ر ﺳﻮب و در ﺳﻪ ﻧ ﺴﺒﺖ آﺑﮕﻴﺮي 0/12، 0/15 و 0/18اﻧﺠﺎم ﺷﺪه اﺳﺖ. ﻧﺘﺎﻳﺞ ﻧﺸﺎن ﻣﻲدﻫﺪ ﻫﻢ ﺗﺮﻛﻴﺐ و ﻫﻢ اﺑﻌﺎد ﺳﺎزهﻫﺎي ﻣﺬﻛﻮر، از ﻣﻮﻟﻔﻪﻫﺎي ﺗﺎﺛﻴﺮﮔﺬار ﺑﺮ ﺗﻮﭘﻮﮔﺮاﻓﻲ ﺑﺴﺘﺮ در اﻃﺮاف دﻫﺎﻧﻪ آﺑﮕﻴﺮ در ﻛﺎﻧﺎل اﺻﻠﻲ و ﺑﻪ وﻳﮋه در اﻃﺮاف ﺳﺎﺣﻞ ﻣﺘﺼﻞ ﺑﻪ آﺑﮕﻴﺮ اﺳﺖ ﻛﻪ ﻗﺎﻋﺪﺗﺎ ﺑﺮ ﻣﻴﺰان رﺳﻮب ورودي ﺑﻪ آﺑﮕﻴﺮ اﺛﺮﮔﺬار ﺧﻮاﻫﺪ ﺑﻮد. ﻫﻤﭽﻨﻴﻦ ﺳــﺎزهﻫﺎي ﻣﺬﻛﻮر و ﺗﺮﻛﻴﺐ آﻧﻬﺎ ﺑﺎ اﺑﻌﺎد ﻣﺨﺘﻠﻒ، ﺑﺮ اﺑﻌﺎد و ﻣﺴــﺎﺣﺖ ﻧﺎﺣﻴﻪ آﺑﺸــﺴــﺘﮕﻲ ﺑﺴــﻴﺎر ﻣﻮﺛﺮ اﺳــﺖ وﻟﻲ رﻓﺘﺎر آﻧﻬﺎ در ﻧﺴــﺒﺖﻫﺎي ﻣﺨﺘﻠﻒ دﺑﻲ اﻧﺤﺮاﻓﻲ، ﻣﺘﻔﺎوت ا ﺳﺖ. در ﺣﺎﻟﻴﻜﻪ آ ﺳﺘﺎﻧﻪ در ﺟﻠﻮي آﺑﮕﻴﺮ ﺑﺎﻋﺚ اﻧﺒﺎ ﺷﺖ ر ﺳﻮب ﻣﻲ ﺷﻮد وﻟﻲ در ﻧ ﺴﺒﺖ آﺑﮕﻴﺮي 0/12،0/15 و 0/18 ﺑﺘﺮﺗﻴﺐ ﻛﺎﻫﺶ 43 و 59 درﺻﺪي و اﻓﺰاﻳﺶ 19 درﺻﺪي ﺑﻴﺸﻴﻨﻪ ﻋﻤﻖ آﺑﺸﺴﺘﮕﻲ در ﭘﺎﻳﻴﻦ دﺳﺖ آﺑﮕﻴﺮ در اﻃﺮاف ﺳﺎﺣﻞ را ﻣﻮﺟﺐ ﻣﻴﺸﻮد ﻛﻪ اﻳﻦ ﻣﻴﺰان ﺑﺮاي آﺑﺸﻜﻦ ﺑﺘﺮﺗﻴﺐ اﻓﺰاﻳﺶ 75 و 75 و ﻛﺎﻫﺶ 49 درﺻﺪي اﺳﺖ و ﺑﺎ اﻓﺰودن ﺻﻔﺤﺎت ﻣﺴﺘﻐﺮق ﺑﻪ ﺗﺮﻛﻴﺐ آﺳﺘﺎﻧﻪ و آﺑﺸﻜﻦ ﺑﻄﻮر ﻣﺘﻮﺳﻂ ﻛﺎﻫﺶ 21 درﺻﺪي را ﺗﺠﺮﺑﻪ ﻣﻲﻛﻨﺪ در ﺣﺎﻟﻲﻛﻪ در ﺗﻤﺎم ﻧﺴﺒﺖﻫﺎي آﺑﮕﻴﺮي ﻫﻢ آﺑﺸﻜﻦ و ﻫﻢ ﺻﻔﺤﺎت ﻣﺴـﺘﻐﺮق در ﺟﻠﻮ و ﺑﺎﻻدﺳـﺖ آﺑﮕﻴﺮ ﻣﻮﺟﺐ آﺑﺸـﺴـﺘﮕﻲ ﻣﻲﺷـﻮﻧﺪ. ﻫﻤﭽﻨﻴﻦ آﺳـﺘﺎﻧﻪ و آﺑﺸـﻜﻦ ﺑﻄﻮر ﻣﺘﻮﺳـﻂ ﺑﺘﺮﺗﻴﺐ ﺑﺎﻋﺚ ﻛﺎﻫﺶ 59 و اﻓﺰاﻳﺶ 155 درﺻﺪي ﻣﺴﺎﺣﺖ ﻧﺎﺣﻴﻪ آﺑﺸﺴﺘﮕﻲ در ﭘﺎﻳﻴﻦ دﺳﺖ آﺑﮕﻴﺮ ﻣﻲﺷﻮﻧﺪ در ﺣﺎﻟﻴﻜﻪ ﺻﻔﺤﺎت ﻣﺴﺘﻐﺮق در ﻧﺴﺒﺖ آﺑﮕﻴﺮي 0/12،0/15 ﺑﺘﺮﺗﻴﺐ ﻛﺎﻫﺶ 28 و 84 درﺻﺪي را ﺗﺠﺮﺑﻪ ﻣﻴﻜﻨﺪ وﻟﻲ در ﻧﺴﺒﺖ آﺑﮕﻴﺮي 0/18 ﺗﻐﻴﻴﺮ ﭼﻨﺪاﻧﻲ اﻳﺠﺎد ﻧﻤﻲﻛﻨﺪ
چكيده لاتين :
Two main goals of water diversion away from rivers are sediment control and water supply with minimum sediment. These goals are commonly accomplished by using some hydraulic structures such as: sills, spur dikes and submerged vanes. These structures make changes in the pattern of flow and consequently the bed topography that lead to control of sediment entry into an intake. Despite their important role in sediment control, the results of previously published works indicate that in some cases these structures can cause substantial scour near the bank at the downstream of the intake on the main channel that may seriously jeopardize the stability of the bank in this area. Using six layouts this report presents the results of an experimental study on the individual and combined effects of these structures (with different dimensions) on the bed topography at the upstream to downstream of main channel and the intake entrance. Furthermore, by measuring the length, width, depth and area, the scour region near the bank at the downstream of the intake on the main channel was qualitatively/quantitatively evaluated. Experiments were performed in a direct flume equipped with a recirculating sediment having a 90° lateral diversion channel at three discharge ratios of 0.12, 0.15 and 0.18 and in six sediment control systems. The results show that both individual structures (in particular, spur dikes and submerged vanes), and their combination, have significant effects on the bed topography at the upstream/downstream of the main channel, the intake entrance, and particularly at the bank connected to the intake that thus affect the amount of sediment entry into the intake. In fact, submerged vanes, by creating a secondary flow, generate a helical motion near the bank connected to the intake causing important changes in the bed topography in an area at the intake. The spur dikes, by flow deviation to the reservoir and also increase in the flow velocity, create a general scour along the flow path from upstream to downstream of the intake on the main channel. Additionally, they, by creating fluid flow in a curved path and thus a helical motion, cause local scour around the bank connected to the intake on the main channel. The results also indicate that these structures and their combination play an important role on the size and area of the scour region near the bank at downstream of the intake on the main channel, but their response varies with discharge ratio. It was also observed that in many conditions sill causes a decrease in the size and area of the scour region at the downstream of intake. Similarly, although submerged vanes cause significant scouring at the upstream and downstream of the intake, in some conditions, they reduce the size and area of the scour region at the downstream of the intake. Last but not least, although spur dike causes a rise in the area of the scour region throughout the main channel as well as the intake entrance, its combination with sill and submerged vanes in some conditions reduces the area of the scour region at the intake downstream.
