Research On Regularities Of Distribution Of The Axial Forces Between Slabs Set In The Ring Of Arch Invert Plunge Pool

Inverted arch plunge pool by high water level and large discharge is an effective measure in protecting riverbed from erosion. But the stability of slabs is one of problems, which are more cared by designers, and also becomes a bottleneck to be overcome in application. In this thesis, main research is aimed at the regularities of distribution of the axial force between slabs set in the ring as well as the possibility of the slab failure in the condition that the water sealed device between slabs is damaged and all anchor rods of slab are out of action. This is of important significance in theory and in engineering application to open out the failure mechanism of the invert arch plunge pool.Firstly forces acting on slabs as they are locked in the ring are made an analysis according to the mechanical equation of equilibrium, and hence a relationship among the axial force, gravity and uplift force is derived to obtain an expression of the axial force.A fine hydraulic model of arch invert plunge pool was designed according to the gravity similarity criterion, in which a key part, a device measuring the axial force between slabs in the ring is well considered. Using the advanced measurement system and fine sensors, many experiments on the axial force between slabs are carried out so as to obtain its laws of distribution both along the flowing direction and the lateral of the ring.The axial force has distinguishing features in the impact vibration zone and the up-downstream vibration one. In the former, the instantaneous axial force changes quickly and greatly. In the beginning area and the terminal of the latter, The lock condition and unlock one of slabs is produced alternately to form an instantaneous arch in the ring. Also, in the middle of the same area, slabs on ring are locked completely for an integral arch or a partial arch in the ring to be formed, But the number of slabs in the partial arch is uncertain, ordinary two or three. When the number of slabs in a ring increases, so does the number of the partial arch in a ring. As a result, the axial force between slabs adds but approaches a constant. The law of the axial force passing shows that it transfers from that locked slab that produces the maximum displacement to the next slabs and then to both slabs at spandrels. The theoretical analysis of the law of the axial force is proved by experiments. The analysis of frequency spectrum indicates that the frequency of the force changing is low, its frequency range is narrow and the dominant one is 0.0-0.2Hz.By the analysis of the relation between the compress resistant of the slabs and its displacement, the invalidation of slab anchor-hold is caused by the common action of the uplift, the axial force and the frictional force. When slabs in arch ring are vibrating in the impact vibration area, the instantaneous stressing tends to exceed the ultimate compressive strength of concrete, while the intensity failure tends to happen in the up-down stream vibration area. The intensity demand of the concrete cannot be satisfied when the displacement of slab reaches seventy percentage of its thickness.