Study On Instability Mechanism And Failure Mode Of The Special-Shaped Plunge Pool

Based on the hydroelastic model of Xiangjiaba,the hydrodynamic load characteristics of the permeable bottom slab with keyway are modeled experimentally by using a variety of advanced experimental instruments and signal processing techniques.By numerical simulation,the failure modes of the permeable bottom plate and the permeable bottom plate with keyway are simulated,and the following conclusions are obtained:(1)With the keyway to increase the permeability of the bottom plate to reduce the maximum lifting force and pulsation value,played a role in reducing load shedding.It is found that the porosity of the permeable hole has the most significant effect of reducing load when the opening ratio is 3.46%.Under the different opening ratio,the probability density distribution of the lifting force basically accorded with the normal distribution.By observing the time history of the lifting force of the measuring point under different opening rate,after adding the permeable hole,the amplitude of the lifting force attenuate significantly.Compared with the power spectrum of the impermeable slab with keyway,the pulsation energy is more concentrated in the low freque ncy,which is beneficial to the stability of the bottom plate.(2)The middle slab is the dangerous point of the bottom slab of the plunge pool through the static calculation of the 3.5% permeable bottom plate with the best open rate,and the maximum displacement of the middle plate is linear with the load before the instability.Through the setting of the non-linearity of the concrete material,the crack area of 3.5% pervious floor slab is analyzed.The cracks are mostly produced in the tensile stress concentration area on the bottom surface of the bottom plate,and the splitting failure is likely to occur.The upper surface of edge slab which has contact with the base of the guide wall prone to cracks,there may be local instability.Through the static calculation and analysis of the decrease of the perforation rate caused by the clogging of the permeable hole caused by the sediment,the single stress of the bottom plate is unbalanced and the failure of the bottom plate is mainly caused by the failure of the anchor.(3)In the best permeable rate of 3.5% with the best performance of reducing load,the keyway improve the overall resistance level of the permeable bottom slab.Under the same lifting force,the overall deformation of the pervious slab with keyway is smaller,and the maximum displacement of the middle plate is linearly related to the load level.The deformation rate of the middle plate is much larger than that of the edge plate,and the middle plate is unstable first because of the anchoring failure.By analyzing of the distributing of the crackers and comparison of the tensile and shear stress,the shear stress of the keyway is less than the shear strength of the key groove,and the shear failure is not occurred.The failure of the middle plate anchorage is the main reason for the plate instability due to the comparison of the static instability of the permeable bottom plate with keyway,which is caused by the clogging of the permeable hole in the sediment.Compared with the cracks,the tensile stress of the keyway is more than its tensile strength and the cracks are densely distributed.When the lifting force is applied,the surface of the keyway damages and mutual locking effect is reduced,resulting in lower opening rate of the pressure drop load capacity decreased at the same time,the lower surface lifting force increases.