| The arch invert cushion pool is an optimized structure for energy-dissipation and riverbed-protection. Hydrodynamic pressure of slabs is a very important factor which leads to instability of the arch-ring by the action of high water head and large discharge.Research on arch invert cushion pool is of great significance in theory and application. This paper summarizes the present results. A fine hydraulic model was designed according to the gravitational similarity criteria.On the basis of theoretical analysis, the experiment on the hydrodynamic pressure on slabs in arch ring has been carried out in the extent of entire flow field. Laws of the pressure distributions both along the lateral and the direction of the flow are obtained to open out the mechanism of formation and change of uplift force, and to propose the way of slabs vibrating. Three conformations of the distribution of hydrodynamic pressure in the base gaps are proposed according to its distribution. After dimensionless processing is applied to the instantaneous maximum and the time-average of the pressure on the surface of slabs and in base gaps of arch ring, it is found that all data tally well. Some formula are given to forecast the mean value of the pressure on the slabs of arch ringThe hydrodynamic pressure has been made analysis in the time zone and frequency one. Characteristics of correlativity at points on the surface of slabs, and in the base-gap and between the entrance to the base gap and the inside are given. The pressure in the entrance has great effect on that in base-gaps. The latter is obvious to spread along direction of the flow in the base-gap. The possible tendency is from skewback to arch crown. The frequency spectrum of the hydrodynamic pressure in base gap is distributed narrower than that on the surface of slabs,but both dominant frequencies are approximating. The fluctuating energy of two is concentrated on the extent of low frequency.
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