Characteristics Of The Hydrodynamic Load On Pervious Slab In Stilling Pool Under The Jet Of Tail-flaring Piers

The joint dissipator of flaring pier and stilling basin is widely used and its effect of e nergy dissipation is go od. However, the flow pattern and characteristics of hydrodynamic load is very complex under the jet of flaring pier.Insatances of damage projects with steel pulled out or plate overturned are common. Therefore, The safety of protecting structure in plunge pool under the jet is the key to success or failure. Given that the projects built, under construction and proposed are facing the security risks the concept of“passive protection”brings, pervious slabs under“active protection”can initiatively decrease the load acting on the pervious slab in pl unge pool and improve the stability of protection structure.Pervious studies are mostly limited to the counter-arch pervious slab in plunge pool, while the research about flat pervious slabs is rarely involved, the studies about characteristics of flat pervious slab can promote people’s understanding of this new protective structure, provide technical information to the research and design units, and promote the applications of“active protection”mode of protective structures.Based on a flaring pier-stilling basin pervious slab hydraulic model tests, on the basis of the research of the hydraulic characteristics of the joint dissipator of flaring pier and stilli ng basin, the text symtematicly studys the hydrodynamic properties of the flat pervious slab, the following conclutions:(1)The text summarizes the hydraulic characteristics of the joint dissipater, and generalizes the energy dissipation mechanism and the flow pattern characteristics of the flaring pier-stilling basin.(2)Time-averaged pressure on the upper and lower surface of the slab gradually increases along the way; the fluctuating pressure distribution both on the upper an d lower surface has characteristics of“Trajectory+underflow”, just amplitude attenuation on the lower surface.(3)The characteristics of t he uplift acting on th e slab in st illing basin are studied ,and the predictive method is put forward; the flaring pier cansignificantly reduce the stilling basin uplift with the largest decline up to 50%.(4)Point and area conversion of the fluctuating pressure is between 0.5 and 0.8,with the distribution the front in plunge pool small and rear large. (5) After the holes(k<0.3%), the fluctuating pressure on upper surface of the slab is essentially the same, while on the lower surface the fluctuating pressure increases in the front of the stilling basin, and reduces at the back; the distribution of the bottom is more closed t o normal d istribution w ith t he per vious co efficient becoming larger; compared with impervious slab, the fluctuating energy on the lower surface of the pervious slab increases, and mainly concentrated in 0~1.5Hz low frequency band.(6)In the view o f the fluctuating pressure correlation between upper and lower surface o f the s lab, the t ext discusses the decompression mechanism o f pe rvious slabs,and the conclution is t hat the pervious slab enlarges the time-space correlation between upper and lower surface of the slab, can reduce the uplift force. When the opening rate is 0.26, the maximum uplift force falls by 10%.