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Pier drilling takes place as part of the construction of the South Parking Garage on the site of the Louisville VA Medical Center July 23, 2023.
At times there were multiple drill rigs working on the site of the Louisville VA Medical Center to prepare the earth for drilled piers.
The last step to complete a drilled pier is placing rebar and concrete.
Rock sockets like these need to be bored out during the pier drilling process to reach the proper depth for maximum strength.
Louisville, Ky. – For most construction projects, progress can be visually measured as structures start to come out of the ground and begin to take shape. This would not be possible without the foundations that transfers the loads of the vertical structures to the soil safely. Part of that foundation work can include the installation of drilled piers.
The Louisville VA Medical Center project recently achieved the completion of a major feature of work by reaching the milestone of “bottoming out” with the installation of the last of 1,057 drilled piers across the site. The drilled piers ranged from 24 to 72 inches in diameter and from five to 35 feet in depth.
All buildings have some type of foundation. Most residential buildings have what is called shallow foundations which generally include spread footings to prevent the building from settling. Drilled piers are a type of deep foundation, which is generally utilized for larger buildings, like the Louisville VA Medical Center, said David Garvin, geotechnical engineer.
“Drilled piers connect structures directly to the bedrock – keeping the building in place by minimizing settlement and lateral loads from outside forces such as wind loads, seismic loads, etc.,” he explained. “Since drilled piers are below the building, they are advanced from the top of the ground until bedrock is reached, with rebar and concrete placed, then the pier is tied into a column or grade beam.”
“Once the drilled pier is tied into the column or grade beam, the steel beams will be placed on top of it. After all steel beams are placed the loads from the entire building will transfer down to the drilled piers and disperse evenly throughout all drilled piers,” Garvin said. “The drilled piers are one of the main components that keep the building in place.”
With drilled piers playing such a key role, it’s important that they are placed with precision.
“There are many things to keep in mind when drilling piers. First, you need to drill through soil until bedrock is reached, this is usually easy to complete but the hardest part is ensuring the pier is drilled at the correct location,” he said. “Then, the drillers will reach bedrock. Once drilling through the rock is complete, the rock socket and bearing surface will be inspected. A professional experienced with inspecting drilled piers will perform a downhole inspection to ensure the rock socket and bearing surface is competent.”
“The last step is cleaning out the pier and placing rebar and concrete. The piers are cleaned out via downhole entry and after the pier is cleaned the rebar will be placed in the pier,” he added.
Garvin said looking back that the work went well with only a few minor issues.
“It seems like the start of this feature of work had it’s challenges, but after identifying the problems and coming up with solutions, the process was smooth sailing,” he said.
Construction is anticipated to be complete in 2026.
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