Numerical and Physical Hydrodinamical Modeling of Skewed Box-culvert

In the construction of land roads and any type of crossing with a stream or channel, it becomes indispensable to install culverts that, due to their hydraulic characteristics, the loading capacity of the soil where they are built, the slope of the land and their filling conditions may have different geometries and dimensions. In Mexico box culverts are commonly used for their very large hydraulic capacity and its support of large embankments, which makes them ideal for low resistance soils.

Sometimes these constructions are not normal to the axis of the road, in those cases, the crossing formed by the natural trajectory of the stream and the road’s axis the construction of skewed works becomes necessary.

In the construction of multi barrel box culverts there are two alternatives: the use of prefabricated concrete box culverts and the construction of on-site culverts, the on-site construction respects within its own system of walls and slabs the skewedness of the drainage system with the road, constructing in the end of each wall a protection structure; in the cases of the use of prefabricated box culverts involves placing lines of them following the direction of the stream, each line of box culverts adjacent to one another has its own pair of walls that also follow the skewedness of the stream with the axis of the road.

The objective of the present work is to model physically and numerically the hydrodynamic characteristics of each alternative and its behavior at the entrance, interior and exit of the water flow in the construction to determine which is the best option to be used on the skewed multi barrel crossings. In order to accomplish this, a variable slope channel and 1: 60 scale models of box culverts with 10, 22 and 45 degrees of skewedness were used.

The results observed in the prefabricated multi barrel box culverts were favorable, due to the fact that the speed spans are lower inside and outside of them, which favors the hydrodynamic behavior of the structure in the river.

This was observed in the physical experiment, where models of skewed culverts were made with the geometries of each alternative, giving a variation between the on-site experimental model and the numerical, physical model of 3.4% and a variation between the prefabricated experimental model and the physical numerical model of 4.8%.