Hydraulic Design of Gabions on Longitudinal Works with the Software Macra Studio

Many times, it is necessary to intervene in hydraulic courses to expand their flow capacity or protect the surrounding structures. Longitudinal works consist of a type of direct intervention, which can be done through the lining or the retention just of the banks, or through the channeling that also protects the bottom of the water course. There is a wide range of materials that can be used in this kind of intervention and one of them is the gabion. Gabions are metallic cages that are filled with rock and united with wire and can be constructed in different formats (box, mattress, etc.) Among all the stages of channels or bank protections design, there is the hydraulic verification. After a hydrological and geotechnical study, it must be verified if the determined section will support the previously estimated discharge, that is, to verify if it will not overflow and if the used materials will resist the flow actions. In general, the gabion longitudinal work design is made based in classical concepts for steady uniform flow, but also contains some particularities that need to be evaluated and considered to specify correctly this kind of material. In order to speed this design up, the software Macra Studio was developed. In addition to the average velocity verification, it is necessary to verify if the velocity of the residual flow that pass through the filling stones and reach the natural bottom is minor than the critical velocity of the soil under the gabion. In the case of the shear stress analysis, the resistance of the gabion depends on the filling rock size and weight, and also can vary with the slope inclination when it is applied on the banks of a water course. All these considerations are presented in this article with the description of the applied method in this software that is used for educational and professional purposes. Although there are specific gabion verifications, Macra Studio can be used for other kinds of lining materials analysis.