Devastating Effects of Hydrostatic Pressure
In the blog post Water is Relentless!, we described the devastating effects hydrostatic pressure can have on a seawall:
“Excessive rainwater or floodwater build-up on the landward side of the wall (usually resulting from an inadequate or clogged weep hole system within the wall itself) will put untenable hydrostatic pressure on the structure. This pressure can cause parts of the wall to move and/or crack. Once the concrete is broken, landward side water will pull soil from your property through the wall and into the water on the other side, causing depressions or small sinkholes near the structure. In addition, steel rebar or mesh inside the wall is exposed to rust, resulting in rust stains appearing on the surface.”
Overview of the Hydrostatic Pressure Release System
Fortunately, a pressure release system can be created by coring through the wall and the layer of SW-RP1 repair material that has been installed behind it during the initial part of the seawall stabilization process. Proprietary pressure release technology is then installed to regulate the release of hydrostatic pressure from any new water that may form behind the wall in the future. Because pressure release technology also stops landward-side soil from passing through the dewatering channels, it prevents new erosion and void formations. The support of high-strength SW-RP1 repair material combined with the regulation of hydrostatic pressure protects your seawall from subsequent movement, damage, or failure.
Components of the Hydrostatic Pressure Release System
- Solidification of Soil with SW-RP1
The contractor injects SW-RP1 behind the wall on the landward side, transforming unstable soil into a permanent lightweight solid mass. This solidified soil provides the perfect supportive medium for the creation of de-watering channels.
- Creation of De-Watering Channels
US Army Corps specifications for seawalls specifically require weep holes to relieve hydrostatic pressure. These channels are generally placed at the same height as the main waterline mark. If there are pre-existing weep holes, these new channels are usually created at those points.
- Installation of Hydrostatic Pressure Release Filters
These filters allow water to pass back and forth to maintain an equilibrium of hydrostatic pressure while also preventing soil migration and void formation on the landward side.
In conclusion, this combined system of soil solidification, creation of de-watering channels, and installation of hydrostatic pressure release filters provides permanent stabilization of the seawall structure. This is all accomplished at 70-80% less than the cost of replacing a seawall. It’s also less destructive to the property because it requires no excavation. Seawalls require maintenance over time, and installation of this system can often be essential in preventing premature failure.