Research On Hydrodynamic Loads Of Underflow Stilling Basin

Energy dissipation by hydraulic jump is dissipating energy mainly by strong turbulence and mix between surface roller and bottom main flow, which is the commo n energy dissipating mode in the discharge structure. Based on the advantages of stable flow, good effect of energy dissipation, slight scour, small atomization range, strong adaptability to geological conditions, energy dissipation by hydraulic jump is very popular in the application to the high dam project.However, due to the considerable high main flow velocity and complex flow condition, the internal relation between dynamic loads and stability of protective structure is still not very clear so far, and the stilling basin slab often subject to flood damage. Therefore, further study of the hydrodynamic load characteristics of energy dissipation by hydraulic jump has important theoretical significance and engineering application value. In this paper, system test about the hydrodynamic loads in the energy dissipation by hydraulic jump was carried on, based on two hydraulic models, 1:50 stilling basin with drop sill and 1:80 d broad tail pier stilling basin with flaring gate pier. The main studies contents are as follows:(1) Based on the model tests, fluctuating pressure and uplift force on the slab of the stilling basin were studied. The relationship among fluctuating pressure, uplift force and total head was obtained. The index that the stilling basin with drop sill can effectively reduce the fluctuating pressure and uplift force significantly was obtained compared with the traditional stilling basin.(2) The fluctuating pressure and the overall load acting on slab of stilling basin and protective slab of side wall were studied. The relationship between the maximum uplift force and fluctuating pressure and the point-surface conversion coefficient of fluctuating pressure were obtained. The stability evaluation index for protection structure based on the parameter of fluctuating pressure was given.(3) The uplift force acting on the middle route of the stilling basin slab, protective slab of side wall and chute slab was studied based on different slab scales, and the relationship among slab scales, spatial integration scale and uplift force were established within the range of test.The reference index for optimizing reasonable slab scale was put forward.(4) In the case of water stop completely destroyed, the uplift force was studied with different penetration degree of gap between the down surface of stilling basin slab and the bedrock.(5) The uplift force was studied under the influence of the intact degree of the water stop. The increasing extent of the possible maximum uplift force was given in the case o f water stop completely destroyed, which provides the reference to predict the possible maximum uplift force in testing the hydrodynamic loads.(6) Based on the model tests, the hydrodynamic loads under the influence of broad tail pier was studied, and the influence degree of fluctuating pressure and uplift force acting on the down surface of pervious slab and impermeable slab under the influence of broad tail pier was presented.(7) The fluctuating pressure characteristics were studied in the pervious pore. The value range of fluctuating pressure correlation coefficient of any two points in the pervious pore was obtained.The fluctuating pressure between inner point and surface point on the same position was compared from two aspects of amplitude characteristic and spectrum characteristic.