Retaining wall reinforcement
The hillsides of Cincinnati, Ohio, are a ticking time bomb. With soft-slide prone clays overlaying steep slopes of shale and limestone bedrock, and a year of intense rainfall like 2018, Cincinnati’s geologic conditions create a recipe for disaster. Scherzinger Drilling worked to repair many residential, commercial, and DOT landslides during 2018 and 2019 … this is a tale of one of the most difficult.
THE PROJECT
Scherzinger Drilling was originally contracted to provide drill only services to Argo Construction for a drilled pier and plug wall at 1737 East McMillan Street on the east side of Cincinnati. The home has a beautiful view of the Ohio River and a steeply sloping backyard that heads downhill towards Columbia Parkway. Due to the heavy rains of 2017, a landslide occurred with a scarp visible on the hillside. Prior to mobilization, a test pit was dug and rock was found 10 feet from the surface. The original design consisted of 13 reinforced piers, each 30-inch diameter by 17 to 25-feet long, and 24 unreinforced plug piers, each 36-inch diameter by 10-feet long.
In October 2018, Scherzinger Drilling mobilized a traditional track-mounted drill rig for this work; however, it quickly became clear that there was a problem. Starting at the end of the wall closest to the driveway, three piers were drilled and the crew found that rock was not 10 feet below the surface —it was closer to 25-30 feet below surface elevation. Not knowing where the test pit had been dug and wondering if this was a localized issue, the drill rig was moved to the middle of the wall to drill a test hole and found similar bedrock conditions. At this point, work on the project was halted and Scherzinger Drilling demobilized as a major redesign would be required.
THE CHALLENGE
The original retaining wall designed Civil Solutions Associates became more involved in the project. They were tasked with drilling test borings, writing a geotechnical report, designing a new retaining wall solution, and acting as the construction manager on the project. The test borings confirmed what the drilling showed; rock was 30 feet below grade, and there was a sloping bedrock profile. The desire from the owner was for the retaining wall to extend the entire width of the property. But with no ability to access the work area from adjacent properties, this left the design team with a dilemma. A bench had already been created to install vertical wall elements; however, tieback installation would have required a working platform hung over the wall, which would have been difficult on a tight residential site.
THE SOLUTION
Scherzinger Drilling was an active participant throughout the design process. The design team finally settled on a design that consisted of two rows of staggered 36-inch drilled shafts that were 45-feet long with a structural mat above tying everything together.
As soon as the design began heading down its final direction, Scherzinger Drilling knew they would utilize its LoDril DH40 manufactured by Bay Shore Systems on the project. The excavator-mounted equipment provided a drill rig with a small tail swing, the ability to place spoils where needed, the ability to reach out and sit away from the shaft opening, and the ability to easily drill both rows of shafts. The DH40 also provided adequate torque and crowd to drill the gray shale and limestone that Cincinnati is known for.
THE OUTCOME
After a winter-long process of redesigning the wall, appropriating funds, and reapplying for a permit, Scherzinger Drilling remobilized to the site in March 2019. Working in tight confines on a hillside proved to be a challenge but one that Scherzinger’s hard-working crew was able to overcome. Production was slow to start, only drilling one or two shafts per day; but by the end of the project, the crew was installing three to four shafts per day.
CLOSING THOUGHT
The speed and ease with which these difficult drilled shafts were installed confirmed that the appropriate drill rig was selected for the job. The LoDril DH40 ensured a safe, productive, and profitable project. Scherzinger Drilling appreciates working with quality equipment produced by a great manufacturer at Bay Shore Systems, Inc.