Sand Sedimentation Mechanism in and around the Railway Culvert and Its Structural Optimization of Sediment Reduction

Abstract

A computational fluid dynamics (CFD) model of a railway culvert was established based on the two-phase flow theory to investigate wind-blown sand transport and sand sedimentation in and around a railway culvert. Then the flow field and the accumulation distribution of sand particles were analyzed through numerical simulation. The results show that the flow field around the culvert can be divided into deceleration, acceleration, and vortex areas. The curve of the horizontal wind speed along the central axis of the culvert had a W shape, indicating a significant increase in the wind speed inside the culvert. A large amount of sand accumulated at the culvert inlet because of the wing walls. The sand volume fraction in the culvert decreased with an increase in the inflow velocity, and there was almost no sand sedimentation when the inflow velocity was greater than 20 m/s. Three reasons for the sand accumulation in the culvert included the deflection by the wing walls, subgrade blocking, and a low inflow velocity. Based on the simulation results, straight and protruding culverts were designed to minimize sand accumulation. The straight culvert exhibited better performance than the protruding culvert and is recommended for use in railways. This work can provide theoretical support for designing railway culverts that minimize or prevent wind-blown sand accumulation.