UMA Delivers Aesthetic Permanent Sculpted Shotcrete Walls
June 6, 2022
UMA Geotechnical Construction typically finishes off the soil nail walls it constructs with a standard shotcrete finish. But sometimes the owner wants a more artistic approach.
That was the case for North Carolina Department of Transportation (NCDOT) on the I-40/I-77 interchange improvements project in Iredell County. UMA was contracted by Lane Construction to install roughly 45,000 square feet of various sized soil nail walls with aesthetically appealing sculpted shotcrete finishes. UMA’s earth retention work was first required to hold up cuts for widened roadway sections and to facilitate new bridge construction.
The NCDOT selected an ashlar stone carved finish, which the department specified to match the previously completed project in 2012 also constructed by UMA at the same interchange. The ashlar finish consists of a random pattern of multiple sized blocks, similar to a natural retaining wall, constructed with stacked stones. The department required a pre-production test panel to be sculpted and approved prior to constructing the sculpted shotcrete walls.
Unlike some decorative cast-in-place concrete wall finishes, there is no form liner involved with sculpted shotcrete walls; all work is physically done by craftspeople. Workers in man baskets do everything by hand, from spraying the shotcrete to carving the artistic patterns.
“With UMA’s normal shotcrete wall, workers use patter boards, grade lines, and levels to make the finished wall flat and smooth,” says Project Manager Brendan Falls. “In this case, they’re using a hand trowel to carve the wet shotcrete into the predetermined pattern the state chose.”
Unlike the soil nail wall behind, which is top-down construction and constructed in horizontal layers, the sculpted shotcrete finish is applied across the entire wall with no particular pattern. Shotcrete nozzlemen work primarily from manlifts, shooting up to 70 cubic yards of material in a single day.
“The crew works in man baskets with a grade lines and levels along with trowels to finish out the pattern,” explains Falls. “The level ensures straight lines in the pattern and verifies that the surface is flat and smooth.”
Once the soil nail wall is constructed, several layers of shotcrete are placed in front of it. UMA starts by attaching a horizontal and vertical rebar in a grid pattern and applying a six-inch layer of shotcrete for the temporary facing. Another six-inch structural layer is sprayed on next to construct the permanent wall facing. The actual carving of the pattern is done when the last two-inch layer is placed.
Despite weather delays, UMA finished the sculpted shotcrete walls on the I-77/I-40 Interchange on schedule in March 2022. Drivers on this heavily traveled new interchange may need some time to learn the new traffic patterns, but at least the view will be good.
An industry leader in the development and refinement of innovative polymer grouting techniques, UMA Geotechnical Construction, Inc. creates specialized solutions to assist clients with ground engineering needs that save money and minimize downtime. As one of the first to use lightweight structural polymers to improve subsurface soils at depth greater than 40 feet, UMA is uniquely equipped to deliver safe, predictable, and effective results. The team includes industry experts in structural support, earth retention, and soil stabilization with decades of experience, and is dedicated to ongoing advancement in the field.
