Remote-Controlled Demolition Equipment Solves Challenging Helical Pier Application
When it comes to fast, efficient deep foundation systems, helical piers are gaining traction with contractors across the country. This anchoring method offers minimal ground disturbance and leaves no spoils. There’s also no cure time involved — unlike micro piles or other systems —allowing for immediate loading and accelerated project timelines. However, achieving these benefits often comes with site-specific challenges, especially in retrofit applications. While helical piers might provide an ideal solution, finding electric equipment with the necessary power-to-weight ratio to access emission-restricted spaces, such as basements and older buildings with low floor loads, can be difficult.
It’s a problem that St. Louis-based contractor Drilling Service Co. faced on a recent warehouse retrofit near the city’s The Hill neighborhood. The location required zero emissions, which limited the company’s equipment selection. The company turned to CSDA member Brokk Inc. for a powerful electric solution. The Brokk 500 not only provided necessary torque, but also offered unrivaled maneuverability that helped Drilling Service Co. overcome several unforeseen challenges to complete the project on time and within budget.
At first glance, the brief seemed straightforward: retrofit a 100-plus-year-old manufacturing facility to support new equipment with heavier loads than the building was designed for. However, site-specific challenges quickly piled up, resulting in a more complex project. The single-story warehouse, located in a traditionally industrial neighborhood near the river, likely sat on contaminated soil, requiring an installation method that limited spoils. Additionally, the facility wouldn’t allow the use of diesel-powered equipment within the building. This meant that even though there was plenty of room to maneuver larger diesel-powered equipment, the selected contractor would need to find an electric solution.
The project’s general manager approached Drilling Service Co. based on their long history of delivering intelligent and efficient underground solutions. The family-owned company, now in its third generation, has been serving the St. Louis area for 66 years. During that time, the company has invested heavily in people and cutting-edge technology, remaining at the forefront of the drilling industry by embracing new methods to provide safe, effective results. For a company synonymous with quality, customer-focused solutions for drilled shafts, dewatering systems, earth retention, micro piles, rock anchors and more, the warehouse retrofit presented a unique opportunity to explore an exciting new process — robotic helical pier installation.
Installing helical piers requires a robust hydraulic system and a specialized drive head that can provide not only downward force, but rotational pressure. Drilling Service Co. would traditionally run the drive head from the auxiliary hydraulics of a mini excavator or skid steer, but with the zero-emission requirement, they knew they’d have to come up with a creative solution. The project required driving large helical piers that were 4.5” diameter pipe with a 16” diameter helical plate 20-25’ down to refuse on bedrock. After establishing the required loads, they reached out to Ideal Group, the helical pier designer and manufacturer, to discuss equipment options.
Ideal connected Drilling Company Co. with Brokk who arranged a one-month rental of a Brokk 500. Ideal Group provided a Digga with a 30ADS anchor drive head and custom mounting bracket. With the rental, Brokk provided training for Drilling Service Co. employees at their St. Joseph, Missouri, demonstration and service center. The Drilling Service Co. team had extensive experience with hydraulic drilling equipment, which gave them some familiarity with the basic functions. However, working with the Brokk robot’s remote operation gave them a new perspective, allowing them to stand back and observe installation from a safe distance. The training covered specifics of the Brokk machine including maneuvering it, setting the outriggers, operating the arm and running the drive head.
With its team trained and the helical piers delivered, Drilling Service Co. was ready to get to work. The general contractor started by saw cutting an approximately 2’ wide section in the 6” thick floor slab running the length of each new grade beam to expose the soil below. However, plans quickly hit a snag when the crew discovered a layer of urban rubble less than a foot below the slab. Operators found grapefruit- to beachball-sized fragments of cement, brick and old rebar from demolished buildings. The helical only has a small pitch and could have advanced through gravel sized rubble, but this was too large.
Drilling Service Co. quickly revised their plan. Before installing the piers, they needed to pre-drill holes through the rubble, which was between 10’-12’ thick. Attaching a 16” diameter core barrel and auger to the drive head, the team simply used the Brokk to drill through the rubble to the soil below.
Once the Brokk created a void through the rubble, the lead of the helical pier was driven through the soil below until it reached bedrock. As installation progressed, 5’ and 10’ sections were added with the team constantly monitoring the drive head and hydraulic pressure for optimal torque output. The Brokk 500’s 23’ reach allowed the team to access helical pier locations and Brokk’s 41kW motor was easily powered by a 100kW generator positioned outside the building.
More than half of the 46 helical pier positions needed to be pre-drilled. With pier installation complete, operators capped the end of each pipe and the general contractor then cast the capped pipe into a grade beam that was reinforced with rebar, becoming the foundation for the facility’s new equipment. Thanks to the professionalism of the team and the versatility of the Brokk, the work progressed quickly, allowing Drilling Service Co. to complete the entire project in just three weeks. With a week left on their rental, the contractor was able to complete another helical pier installation, this time at a St. Louis landmark.
The Muny, a permanent outdoor theater in Forest Park which hosted its first production in 1916, was installing an elevator as part of a larger renovation project. The project required 17 helical piers of the same size Drilling Service Co. was using on the warehouse retrofit. With the Brokk already equipped with the drive head, the team was able to quickly relocate to the new jobsite. The crew could only access the elevator shaft through a narrow pergola, so the compact size of the Brokk, with 5’ x 3” transport width, provided a huge benefit. Additionally, the reach and maneuverability of the Brokk’s three-part arm increased efficiency, allowing operators to access several piers from a single spot, minimizing the need to reposition the machine in the confined space.
The Muny project wrapped up in a week and Drilling Service Co. retuned the Brokk 500 — until the next time. “At heart, we’re a company of problem solvers who is always looking for new ways to increase safety and efficiency,” said Kyle Murphy, Project Engineer for Drilling Service Co. “Everyone on the team brings their best ideas to the table. When we were approached with this project, we recognized it as an opportunity to explore new equipment options.”
Drilling Service Co. is a specialty contractor based in the Midwest involved in the construction of drilled shaft foundations, large diameter shafts, earth retention systems, rock anchors and tiebacks, micropiles, helical piers, dewatering systems, limited-access drilling, and pressure grouting. With over 65 years of history working in every conceivable subsurface condition, Drilling Service Co. offers the best possible combination of sophisticated technology, modern equipment, knowledgeable and professional personnel, and proven, practical experience.
General Contractor: Drilling Service Co.
CSDA Member: Brokk Inc.
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Methods Used: Robotic Demolition