Alchatek Blog

Seawalls are built to create a strong and stable barrier between a body of water and adjacent land, but why do they fail over time? Here are three common factors that can damage a seawall.

Soil Erosion

Incoming tide water pushes against a seawall and through cracks, joints, and defects. Over time soil erosion can occur on the inside of the wall. When the tide falls, water flows out and this erodes the soil, thereby weakening the structure. Soil erosion will begin to form small sinkholes in the corners of the inside section of a seawall. During periods of heavy rainfall, this problem worsens, and the deterioration process speeds up. Sinkholes are one of the earliest signs of trouble for a seawall.

Clogged Vents and Weep Holes

Constructing vents and weep holes in the seawall to allow the water behind it to drain and pass through is good practice in order to prevent pressure build-up. Unfortunately, when debris forms and blocks these holes, the channel for water passage seizes to exist. This can then cause the pressure build-up to occur. After some time, the pressure can crack the seawall and the water may find other flow passages causing unwanted soil erosion. 

Natural Disasters

If you live in an area that is susceptible to hurricanes, a seawall will very likely take some damage during hurricane season. The powerful winds erode soil from the back of the seawall to create sinkholes and voids. A lot of this damage can be prevented by reinforcing a seawall for the hurricane season.

Polyurethane Seawall Repair

You can greatly extend the life of a seawall by reinforcing or repairing it with semi-rigid hydrophobic polyurethane foams that react with moisture in the soil and expand to fill voids while they permeate sandy soil to form a solid, strong, watertight mass.

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I'd like to share a case study from a recent job that I consulted on with one of our contractor customers, ETRU Spray Foam and Coatings and Coatings in Southern Illinois.

A 25’ x 40’ residential pole barn in Carbondale, Illinois was built on a 6” floating concrete slab on grade. The concrete was poured into four 10’x 25’ sections. Each section had multiple cracks and breaks throughout, and in some cases, the broken sections had a drop of up to 3”. During the inspection, it was discovered that the pole barn 4 corner beams were driven into the ground and the concrete poured around them. The front of the property was pitched towards the pole barn and it showed no signs of ever having gutters and downspouts attached. After drilling an injection hole, we inserted a probe to check the depth of the void and the stability of the ground. In some areas the void was 6” and the probe was hand driven to a depth of 3’ before hitting hard ground. ETRU Spray Foam and Coatings was hired to stabilize the ground and level as much of the concrete as they could. The homeowner plans to utilize the space as a game room.

Powerful Polymer

Among the most dependable products for geotech applications, AP Lift 430 structural foam provides an exceptional DOT grade solution for these types of situations. This 3 lb. density, high-strength, hydro-insensitive structural polyurethane foam is perfect for densifying soil and lifting concrete slabs.

Painless Procedure

The ETru crew and I walked the project with both property owners. We pointed out how waterlogged the ground was and that they needed to add gutters and downspouts, as well as pitch the ground water away from the pole barn. We also talked about possible blowout from under the slab during the injection process and how to handle it. I worked with ETRU to draw up a plan, indicating exactly where the injection points would be located (knowing that the plan might change due to the ground moisture and the number of voids to be filled). All injections were completed from inside the pole barn with a crew member on the outside to alert us when product broke through the ground. First, we injected in the back corner which had the 3” drop. The plan was to establish a base slab height on the side with the most soil problems and then level everything else to that slab. Spacing between injection points was approximately 3-4 feet, with 38 total injection locations.

Rapid Result

The ETRU Spray Foam and Coatings crew achieved a three-inch lift and was able to bring all the other slabs within 1/8” from the adjoining slab. The customer was extremely happy with the results.

Video Footage

Want more info on lifting slabs with polyurethane?