While completing routine highway maintenance in Presidio, the Texas Department of Transportation (TXDOT) discovered that during high intensity storm events, the water flowing off the bridge was causing scour and erosion issues around the piers and abutments. A solution was needed to protect the piers, while also dissipating the water flowing off the roadway and hitting the bridge abutments.
As a solution, a total of 245 units of 48-in A-Jacks® were selected for the ability to provide energy dissipation and protection against scour and erosion. In addition, 24-in gabion mattresses were utilized at the top of the bridge abutment for its ability to dissipate the energy flowing off the roadway.
The concrete hard armor units arrived at the site on pallets, facilitating the staging of materials. During installation, it was necessary to place the A-Jacks underneath the bridge without damaging the existing piers and without having to close the bridge during installation. It was critical that the piers remain intact in order to avoid future repairs to the existing bridge structure. This was accomplished over a six week time period with a backhoe and basic labor that involved placement of assembled individual A-Jacks units.
The interlocking A-Jacks units are designed to create a flexible, highly permeable matrix to dissipate energy, resist the erosive forces of high-flowing water and protect against future scour and erosion.
Due to the inclined, 45’ high abutment, it was a challenge to install the gabion mattresses. As a solution, the protective armor around the abutment was removed so that the gabion mattresses could be installed in steps.
According to Oscar A. Arzaga, Engineering Assistant, with TXDOT, “The overall success of the project was excellent. The A-Jacks were installed very quickly with no change orders, and we are very pleased with the end result.”