Study On Different Forms Of Slope Protection Structure Of Plunge Pool Of Wudongde Project

Wudongde water complex project is another big project in southwest China,and the flood discharge problem of Wudongde Dam is the major issue of this project.Big water complex in southwest China has characteristics like big flood discharge,strong discharging power and big discharge per unit width and the Wudongde Dam faces the same challenge.The purpose of this research is to investigate the flow characteristics of the plunge pool during flood discharge,the performance and loads of all kinds of different slope protection lining slabs under flood discharge and discuss the safety and stability of different types of slabs and provide support for the lining design of the plunge pool.Focusing on the cushion pool with lining slope but without bottom protection of Wudongde Dam,experiments of pervious slope protection,pumping drainage slope protection,self-drainage slope protection and slope protection without drainage system were conducted and the correlation of fluctuating pressure acting on the upper and lower surface of the slabs was analyzed,and up-lifting experiments of pervious slope protection and slope protection without drainage system was conducted to study the up-lifting force characteristics.And the pressure difference of the upper and lower surfaces of the slabs under the influence of the fluctuation of the water surface and waves induced by flood discharge was investigated and the drainage performance of all sorts of slope protection was analyzed.(1)Wudongde Dam's plunge pool creates a deep and wide water cushion and the discharge jet does not impact directly on the slope protection and bottom of the plunge pool under big flood discharge.The time-mean pressure on the slope protection and bottom of the plunge pool show static pressure characteristic and the pressure difference between test points are little because of the water surface fluctuation induced by flood discharge and natural variation of the shape of the plunge pool.The fluactuating pressure on the slope protection and bottom is not severe and the maximum standard deviation is 1.56 m.The fluctuating pressure distribution over the plunge pool was influenced by the flood discharge and way of discharge,but the pressure fluctuation maintains on a low level and plunge pool isn't compromised by the severe vertex of the flood jet.(2)The correlation of fluctuating pressure on the upper and lower surface of the slabs of all four types of slope protection was investigated.It was found that when the drainage system fails,the synchronism of fluctuating pressure acting on the upper and lower surface is not good,and the phase difference is big and would probably cause high value of pressure difference which could lead to high up-lifting force.However,pumping drainage slope protection and self-drainage slope protection could cut the phase difference respectively.Pumping drainage slope protection has limited performance of reducing the phase difference but the self-drainage slope protection can dramatically decrease the phase difference and reinforce the synchronism the fluctuating pressure of the upper and lower surface.The pervious slope protection has the best performance of reducing the phase difference and reinforcing the synchronism.Only little pervious ratio of the slabs could largely enhance the synchronism and the pervious holes on the slabs could connect the joints and water flow in the plunge pool.(3)In order to investigate the performance of reducing loads of pervious slope protection,up-lifting force experiment was conducted and the overall up-lifting force is on a low level and it's slightly high when flood discharge is big.In addition,although the pressure experiment before proved that little pervious ration could synchronise the fluctuating pressure desirabally,the pervious ratio needs to reach a sertain level to reduce the up-lifting force efficiently,and when the ratio is 3.6%,the maximum up-lifting force on the slabs decreased dramatically.(4)Wudongde plunge pool would create a huge volume of energy dissipation water,so the discharge protection structure could avoid direct impact from the discharge jet and the major problem of the protection structure turns out to be the difference of water head caused by the surging and fading of the waves of water in the plunge pool.Experiments were conduceted on a certain altitude to investigate the difference of water head between two sides of the slabs.The analysis shows that the pervious slope protection and self-drainage slope protection could drain the water from the joints and reduce the water head difference to maintain the stability of the protection slabs.