Coring is the process of removing a cylindrical sample, or core, from soil, rock, or paved surfaces. Workers secure these samples using special core drilling machines, which can range from portable models to large-scale industrial units. The core drilling process is similar to using a hole saw to cut wood, but is designed to saw through much tougher materials. Coring can be used to investigate subsurface conditions or to test the strength and stability of soil or paving.
Core drilling machines come in a variety of designs and configurations to meet the needs of different coring applications. Most use some form of circular steel blade with diamond cutting tips. For small indoor projects, a simple motor-powered diamond blade may be sufficient. To drill through tough rock or concrete however, workers utilize core drilling machines powered by pneumatic or hydraulic systems to generate extra force and cutting power. Vibracoring, which utilizes a vibrating action to enhance cutting power even further, can also be used to penetrate harder materials.
Once a coring sample has been removed from the earth, it is ready for testing and inspection. These samples generally retain their cylindrical form, and the different layers allow workers to examine changes in subsurface conditions over time. For example, a core taken from an asphalt road will likely reveal fresh asphalt at the top, older layers in the middle, and concrete or soil at the base.
Both destructive and non-destructive coring test methods may be utilized. Destructive methods include taking smaller samples out of the side of the core, or subjecting the core to crushing or other forces to test its strength. Non-destructive methods may include MRI or ultrasound technology, which use invisible waves or magnetic imagery to examine the structural makeup of the core.
Coring plays an important role in many aspects of modern life. Builders may rely on this process to cut manholes in a paved street, or to cut through a concrete wall in a building while installing water or sprinkler piping. Mining or energy companies utilize this technology to find subsurface deposits of oil, minerals, and metals. Paving crews take core samples to test the strength of a road, while engineers use these samples to test the stability of a concrete building or bridge. Geologists and historians rely on coring to study the earth in layers and to gain an understanding of the history and composition of the planet.