28 JULY 2023 WorldWide Drilling Resource® Blasting Massive Underground Caverns for Neutrino Experiment Adapted from Information by Sanford Underground Research Facility (SURF) Deep below the surface in South Dakota, construction crews have been working tirelessly to carve out a network of caverns and tunnels which is destined to house a huge neutrino experiment. To create these caverns, a total of approximately 800,000 tons of rock will be excavated. Thyssen Mining Inc., the company contracted to carry out the excavation which began in 2021, has extracted nearly 400,000 tons so far, bringing the project to its halfway mark. Once finished, the Long-Baseline Neutrino Facility (LBNF) will be the site of the international Deep Underground Neutrino Experiment (DUNE). More than 1000 scientists and engineers, from more than 30 countries, will use the facility to study neutrinos, elusive particles which could hold the answers to many of our universe’s mysteries, such as why it is made of matter and how black holes and neutron stars are born. The new underground area at SURF will consist of three large caverns - two measuring around 500 feet long, 65 feet wide, and 90 feet high. The third will be around 625 feet long, 65 feet wide, and 36 feet tall and contain cryogenic support systems, detector electronics, and data acquisition equipment. The first half of the excavation involved several important steps: mobilizing large equipment underground; creating a ventilation shaft; carefully creating a network of tunnels known as drifts; and excavating the enormous caverns. Moving the heavy mining equipment underground was no simple task. It involved taking the equipment apart, lowering the parts a mile belowground through a narrow shaft, then reassembling the machinery underground. One of the pieces of equipment brought underground was a raise bore machine, which was used to create a ventilation shaft for cooling and to provide airflow to the caverns. To create the shaft, workers used the raise bore machine to drill a 13¾-inch pilot hole, attached a 12-foot-diameter reamer head to the drill stem, and backreamed the pilot hole to form a borehole 1200 feet in height. Once the equipment was underground, construction crews began excavating the drifts, an interconnecting highway of tunnels connecting the three caverns. To form these underground tunnels, miners used the drill-and-blast technique, which involved drilling a series of blastholes, filling them with explosives, and blasting away the rock. Construction crews used the same method to excavate the caverns. One of the major milestones during the first half of excavation was completing the caverns’ top headings, the dome-shaped upper section of each cavern. This involved excavating a small pilot tunnel to assess the geology and groundwater conditions, then enlarging the sides to create the full span of the caverns. Both the drifts and cavern top headings will be reinforced with ground support anchors, wire mesh, and sprayed concrete. Teams will also pour concrete floors in the base of the caverns and all the interconnecting drifts. Once complete, they will move the construction machinery out of the caverns by breaking down the equipment into smaller pieces and sending the components up through the shaft to the surface. Completion of the top headings will set the stage for the next phase of excavation, which includes drilling and blasting downward from those headings to carve out the rest of the caverns. With the second phase of excavation now in full swing, the project is expected to be completed in 2024. Safety has been paramount during construction. Ryan Moe, the U.S. general manager at Thyssen Mining said, “Our safety record underground has been very good, and we would like to continue to the end of the project with nobody getting hurt. Second to safety, is to deliver a high-quality project, and everybody’s been happy with the quality of the work that we’ve done.” Photo by David Smith, Fermilab. EXB
RkJQdWJsaXNoZXIy NDk4Mzk=