Coring

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Rock Core Samples

Rock coring is used to obtain in-situ rock / soil samples and strength parameters through tests such as the Standard Penetration Test (SPT). "Cylinder samples from 4 to 8 inches in diameter and 6 to 12 inches long... may also be obtained by jacking or otherwise pushing drive samples into exposed surfaces using a continuous steady pressure. Hydraulic power equipment may also be used to push Shelby tubes into exposed undisturbed soil to collect undisturbed samples, such as the sampler mounted on a backhoe."

"Rock core drilling is accomplished with mechanical, engine-powered rotary drills designed to drill rock and to recover cylindrical cores of rock material. Most core drilling equipment is designed with gear or hydraulically driven variable-speed hollow-spindle rotary drill heads. Average core-diameter capability of these drills ranges from 19 to 85 mm (3/4 to 3-3/8 in) and to 300-m (1,000-ft) depths. Larger-diameter coring operations [100 to 150 mm (4 to 6 in)] are usually performed using rotary drills, and cores to 1.8 m (6 ft) in diameter can be drilled and recovered using a shot/calyx drill."

"All core drills are equipped with pumps or compressors to circulate drill media through use of water, drilling mud, air, or air-foam to cool and lubricate the coring bits and to transport the drill cuttings to the top of the hole. Most core drills are equipped with a mast assembly, powered hoist assembly for hoisting heavy loads, and, sometimes, a wire-line hoist assembly for hoisting or lowering a wire-line core barrel through the drill rods."

"Many variations are available in design and mountings for drill rigs manufactured specifically for coring; however, there are only two types basic types. They are conventional or wire-line core drills, for drilling and recovering cores up to 150 mm (6 in) in diameter, and shot/calyx core drills for drilling, and recovering cores to 1.8 m (6 ft) in diameter."

Best Practices Resources

Drilling and Invasive Activities at Dams and Levees (ER 1110-1-1807), USACE, 2023

National Engineering Handbook: Chapter 5 - Engineering Geology Logging, Sampling, and Testing, NRCS, 2012

National Engineering Handbook: Chapter 2 - Engineering Geologic Investigations, NRCS, 2012

Design of Small Dams, USBR, 1987

Citations:

Revision ID: 6860
Revision Date: 06/15/2023