Introduction. Eroded processes on the plains are substantially different from riverbed deformations, due not only to their geological structure but also to the presence of vegetation. A large number of experimental and numerical studies on the distribution of the high-speed structure and depth have been carried out in order to predict the blurred processes on the flood plains in the area affected by bridge crossings. The question remains as to how many features of flood plains in the area of the bridge opening should be taken into account.
Problems. In the design of bridge crossings, the most interesting value is the maximum deformation that can occur while the operation of a bridge during a design flood or flood. Accordingly, in calculating the deformations not only in the bed but also in the floodplain in the area of the opening of the bridge, it is important to establish the maximum depths, which reasonably determine the required depth of laying the foundations of the bridge supports.
The aim of the work. Forecasting of maximum swells in flood plains, taking into account the force of resistance at the fairing of bridge supports.
Materials and methods. This paper is based on the theory of mechanics of a continuous environment, heterogeneous flows and the theory of shallow water, mathematical modeling methods, numerical modeling methods.
The calculation in the zone of influence of bridge supports is carried out according to the equation of the transfer of the speed of floodplain flow with grass vegetation, taking into account the force of the resistance during the flow of bridge supports. The numerical implementation of the proposed mathematical models on iterative methods for calculating the hydrodynamic characteristics of floodplains with vegetation has necessitated the formulation of initial and boundary conditions to take into account the characteristic features of flood fluxes in the zone impact of bridge crossings.
Results. A two-dimensional mathematical model has been developed that makes it possible to take into account the features of the flood plains concerning the distribution of vegetation, the winding and the resistance when the bridge supports are rounded.
According to the proposed method, the hydrodynamic indicators of the flood plains of Severski Donets on the T-05-14 road in the Donetsk region were determined, including the longitudinal velocity, taking into account the resistance force of the fairing of the bridge supports and the marking of the bottom region after the passage of the flood down the design staircase. The maximum longitudinal velocity at the beginning of the dip varies between 2.45 m / from 2.32 m / s, respectively, on smaller and larger plains. The depth of the bottom erosion varies from 0.19 m to 1.91 m in the lower floodplain and from 0.035 m to 2.75 m in the greater floodplain.
Conclusions. The proposed two-dimensional mathematical model of the floodplain flow makes it possible to determine the distribution of average velocities and depths in accordance with the consistency with the pressure field and taking into account the characteristics of the area under investigation with supports on the floodplain sections in the bridge bridge bridge tail. On the basis of the results of its numerical implementation in the section of r. Severskiy Donets, the value of the maximum dilution has been established, which is the starting point for the determination of the depth of laying the foundations of the bridge supports. The maximum melting depth at the higher floodplain is 2.75 m, and at the lower plain is 1.91 m, which is due to the effect of the drag on the fairing of bridge supports and the compression of the flow between them.
