Technical Foundations drilled holes with a KLEMM KR 806-3G and inserted lengths of rod and casing into the rig with an excavator-mounted HBR 120 rod handler on a micropile project near Roanoke, Virginia.
technical basics has been providing civil engineering contracting services along the East Coast for 27 years, with a strong focus on Virginia and the Carolinas. The contractor’s reputation for taking on unique projects is evident in the choice of equipment, most recently in the rental of a CLAMP Drill rig and rod handler from Equipment Corporation of America (ECA).
“Technical Foundations specializes in unique projects,” said project engineer Butch Stoneman. “We like to offer cost-efficient, innovative solutions and sustainable soil improvements for demanding locations where conventional approaches don’t quite work.”
The contractor has been doing business with the ECA Washington office for more than 10 years. Although the initial connection was with branch manager Mike Brown – known to Stoneman and many other contractors for his extensive knowledge of the KLEMM product line – it was Account Manager Greg Barta who arranged the rental of the drilling rig and rod handling equipment.
KLEMM drilling rigs are no stranger to Technical Foundations, but ECA’s KLEMM specialist Burt Kerns was deployed at the start of the project to train the team on site as this was the contractor’s first use of the HBR 120 rod handling device.
Micropiles selected to avoid disturbance
Technical Foundations commissioned the KLEMM rig and handling system on a project near Roanoke, Virginia in January 2021. The contractor was hired to install 230 micropiles to support a sizeable commercial building extension and multi-storey prefabricated car park.
The micropiles would be spread over the roughly 2 hectare site to support the proposed structures in unsuitable soils. The existing site was essentially a valley that was filled in with various materials to level it.
The technical basics began with test drilling to locate the bedrock. It turned out that an unsuitable filling would make it impossible to build the structures on a conventional splayfoot without settlement problems.
Various deep foundation systems were considered. The existing business would remain fully operational so avoiding disruptions was critical. Driven piles were eliminated primarily because of the vibrations that would occur during pile driving and heavy equipment.
After several stress tests, it was determined that 6 inch diameter piles would achieve the correct capacity. They should be grouped in a pile cap configuration around the building supports and under some of the leveling boards.
Micropile drilling with the KLEMM
The KLEMM KR 806-3G was the most important workhorse for micropile drilling. Technical Foundations had several other drilling rigs on standby.
“It was more efficient with one drill bit focused on drilling and the other focused on grouting the holes,” said Stoneman. “It was also a very tight schedule, so we had an extra machine out there to make sure our workflow wasn’t interrupted.”
The KR 806-3G drilled stakes 20 to 65 feet deep and set them 5 feet into the rock. The top layer of filler material was usually soft and damp and contained a mixture of concrete rubble, tree roots and various types of soil that were up to 40 years old. The native soil underneath was a weathered rock, which was underlaid by rock.
“We chose the KLEMM because it was the most reliable machine we had available and with its various functions it would be a bit more versatile in difficult drilling conditions,” Stoneman said, referring to the drill rig’s electronic switching capabilities, which enable a change in torque and speed.
The double-head drilling capability of the KR 806-3G was also an advantage, as it has separate drives for the outer housing and the inner rod. This was especially helpful when drilling through different types of materials and formations.
KLEMM bar handling device increases productivity
KLEMM drilling rigs can be equipped with a MAG 7.0 turret, which is ideal for deep foundation methods such as tie rods or pegs where the housing is reused. The KR 806-3G technical foundations rented as part of the Roanoke project did not have a turret, as micropile sleeves are used once. The HBR 120 rod handling attachment proved to be more suitable.
The drilling crew would drill a hole with the casing and inner rods. The operator of the KR 806-3G would leave the housing in place and pull on the inner bars. The inner rod was then gripped with the HBR 120 and fed back into the next part of the housing.
“When the crew was ready to drill the next hole, they were all ready,” said Stoneman. “Because the housing and rods were preloaded, they could drill at a faster production rate.”
The smooth flow of the micropile drilling process has nearly doubled productivity compared to the construction company’s traditional method. Technical Foundations traditionally used the winch to lift the housing and inner rod and make the connection by hand. The contractor would typically reach 6 to 8 micropiles a day using this method, compared to 14 micropiles he made with the KLEMM rod handling attachment.
“The bar loader holds the inner bar and casing still so we can connect to the drill head,” explains Stoneman. “The operator of the drilling rig can loosen both joints and then lift his head up so that the transition to the next piece of drill steel is quicker.”
The HBR 120 fits any make of excavator, but Technical Foundations has designed it on one Komatsu. Attaching the attachment was easy. The contractor built an adapter that made it easy to attach the rod handler to the arm with pins and bolts. A piggyback system made it easier to connect hydraulic hoses and electronics to the excavator’s fuse block. This allowed the operator to easily control the functions of the rod handler, including rotating, tilting, and clamping the housing and inner rods.
The HBR 120 can rotate on a 360-degree axis, but Technical Foundations did not require that amount of movement on this project. The greater focus was on getting the rod handler and derrick on the right level to keep the housing properly aligned for the sections to thread properly.
This process required careful communication between a spotter and the drill rig and excavator operators. The KLEMM rig was operated remotely so he had the flexibility to move into a position with better visibility. The spotter used hand signals to help both operators align the joints properly.
Taking security to a new level
The KLEMM rod handling accessories also improved safety for the technical foundations’ ground staff. The 10 foot inner rod and housing sections weighed approximately 300 lbs., Which has the potential to cause serious injury.
“By using the rod guide, you reduce the chance of a section of pipe coming loose and falling and injuring someone, but you can also remove people’s hands from their joints,” said Stoneman. “If you can completely eliminate serious injury or any possible human contact, it is a positive thing.”
The ability to remotely control the KLEMM drill contributed to the safety of the micropile drilling process. The groundwater kept dust control to a minimum on the Roanoke project, but the ability for the operator to move into an area with improved visibility was helpful.
“The remote allows the operator to position himself outside of the dust that can be created by drilling and in a place where he can best see what is going on,” said Stoneman. “The further away you are from the machine, the safer the operator is.”
Missed deadline despite additional micropiles
The owner of the Roanoke project had a final opening date for this building so he couldn’t extend the schedule, according to Stoneman. To make matters worse, the owner asked for 40 additional piles between the submission of the bid and the start of the project.
Technical Foundations arrived at the Roanoke project on site in January 2021 and was completed in late February 2021.
Stoneman said, “Our crew went through some extreme conditions and the equipment improved productivity, so we finished the job several days ahead of schedule, even after we started about a week late.”
For the Roanoke project, Technical Foundations rented the KLEMM drill rig and rod handling equipment from ECA. After completion, the safety and productivity gains combined with the potential for future projects made it easy for the contractor to choose the HBR 120. At this point, Technical Foundations did not have enough relevant work to keep the KR 806-3G constantly busy.
“We were extremely pleased with the productivity and safety it offers [HBR 120] added to the project, “said Stoneman.” We see several places where it will benefit us in the future.