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Soil Nails Installation Project: Retaining Wall Stabilization Location: Bellevue, TN

Challenge:

 

About two years ago, our team completed concrete lifting and repair on the driveway of Carolyn and Richard of Bellevue, TN. Recently, they called us for some routine service as the caulk we installed connecting their driveway with a retaining wall was cracking and they wanted us to inspect it.

 

Upon further evaluation, our specialist not only noticed cracks in the caulk, but also some stairstep cracking in the bricks of the wall itself which is typically indicative of structural damage. Their home was located on a hill. The driveway was located at the top of the hill and held level on the slope by the retaining wall made of block and covered by a brick veneer. The 32’x24’x8’ wall showed no settlement when a laser level was placed on it, however, it was bowing outward about 1” starting at the 19’ mark of the backside.

 

Carolyn and her husband decided that we had provided them with a remarkable experience with their concrete lifting project, and they wanted us to provide a solution which would stabilize the wall and prevent further movement, while also potentially being able to lift the wall to its original position.

Solution:

 

This was a tricky fix for us as the way the structure was positioned on the hill meant some of our more common solutions wouldn’t be possible as we didn’t have access to the inside of the structure like we would with a basement or crawl space. Even considering the adversity, our specialist was dedicated to finding a solution.

 

After a thorough inspection, he recommended using Helical Soil Nails drilled into the soil underneath the driveway, which would then be connected to the wall to prevent further movement. The soil nails are attached to a threaded steel rod which is then fed through a wall plate screwed onto the wall itself. The bolt on the outside of the wall plate can then be tightened around the rod during dry seasons to potentially straighten the wall over time. The proposed plan for this project was to use 6 Helical soil nails, 3’ from each corner and 5 ½’ from each other to stabilize the wall.

 

The first step of this process was to cut holes in the wall to make room for the blades of the soil nails to get through. The crew experienced an unexpected issue when they noticed that the block wall was actually not fully attached to the brick veneer. This meant that attaching the wall plates to the brick veneer would not be able to stabilize the wall as the block was likely the issue. This challenge was easily overcome by removing just enough brick that a wall plate could be attached to the block behind.

 

Once the holes were created in the wall it was time to spin the soil nails. Each soil nail was made up of a helical blade on the front end and 2 leads with each section being about 5’ in length. Then a small cap on the end which linked the nail to the threaded steel rod. The soil nails were installed using a Helical Drive Head attached to the end of a mini-excavator and spun a little over 15 feet deep into the ground. Once the soil nails were installed, the threaded rod was then screwed into the cap on the end of the nails. The rods were fed through wall plates which were then attached to the exposed block wall underneath the brick veneer. The final step was to cut off the excess rod sticking out of the wall plate.

 

This project was completed in only one day and both Carolyn and Richard are very pleased with the results and the security that their wall will be staying put. They hope that with time, our solution can eventually bring the wall back to its original position.

Project Summary Specialist: Mike Lattero Team Leader: Michael Gunsolus Materials Used: Helical Soil Nails (6), Leads (12), Wall Plates (6)