A power-driven undisturbed soil core sampler was designed to obtain undisturbed
soil cores from a much greater depth than the original hand-operated sampler

Hayden, C.W.

Robbins, C.W.

USDA - ARS - NWISRL

SOIL SCIENCE	 Vol. 120, No. 2Copyright 0 1975 by The Williams & Wilkins Co. 	 Printed in U.S.A.NOTEMECHANICAL SNAKE RIVER UNDISTURBED SOIL CORE SAMPLER'C. W. HAYDEN AND C. W. ROBBINSSnake River Conservation Research Center, Kimberly, Idaho 83341Received for publication March 19, 1974ABSTRACTA power-driven undisturbed soil core sampler was designed to obtain undisturbedsoil cores from a much greater depth than the original hand-operated sampler.This note is in response to the many inquiriesconcerning the handoperated Snake RiverSampler for obtaining undisturbed cores (Hay-den and Heinemann 1968) and the possibility ofobtaining samples to a much greater depth.Although the original sampler worked well inthe upper 50 cm, we needed a unit with a powerdrive to obtain undisturbed cores to bedrock(Fig. -1). The advantage of the new sampler isthe ability to sample to much greater depthssimply by adding an outside auger tube withouthaving to pull the entire sampling equipmentout of the soil. The unit can be converted to, ormounted on a small trailer, which can be pulledby car or pickup truck. This makes the samplerhighly maneuverable for sampling in areaswhere larger units could not operate.The power-driven undisturbed core samplerwe developed can be adapted to any unit with arotating power drive. A direct-drive, 9-hp gaso-line motor with a centrifugal clutch powers thedrilling unit of the modified sampler. A two- orthree-speed transmission with a hand-operatedclutch would be useful, especially in samplingwet soils where slower turning is desirable toprevent the sampler from drawing down fasterthan soil can be removed from around thesample.The construction and purpose of the cuttingtip of the deep sampler is the same as that of theoriginal sampler. That is, the inside sampletube remains stationary while the outside augertube removes the soil away from the sample.Contribution from the Western Region, Agricul-tural Research Service, USDA; University of IdahoCollege of Agriculture Research and Extension Cen-ter, Kimberly, cooperating.The sample tube and split sleeve holder has aslightly larger diameter than the spring steelcutting tip. This allows the sample to slip intothe split sleeve holder without any distortion orcompaction. The I.D. of the split sleeve wasscaled down from 8 cm (31/4 in.) to 5 cm (2 in.)and the split sleeve lengthened to 51 cm (2 ft).The split sleeve holder is 63 cm (25 in.) long andthe outside tube is 91.5 cm (36 in.) long.Several auger tubes were constructed to ex-tend the auger tube until desired samplingFm. 1. Mechanical Snake River Sampler in opera-tion.153Clamp —4,-—.-Power drive4 Jaw chuck—+drill rodThreadeddriving plugFlanged insert•--Outside auger tub.Split sleeve holder —•154	C. W. HAYDEN AND C. W. ROBBINSdepth had been reached (Fig. 2). After obtain-ing the last sample, the outside auger tube israised while it continues to rotate in the samedirection as during sampling.A four-jaw chuck (Fig. 3) is permanentlyconnected to the power drive. This allows thehollow drill rod to extend through the gearhousing. A threaded driving plug welded to thelower end of the drill rod screws into the top ofthe outside auger tube.The split sleeve holder has two left-hand1-shaped notches cut on opposite sides of theupper end. An insert was machined with twoflanges so that, when turned counterclockwise,it locks under the lip of the L-shaped notch. Theinsert holds the sample tube and split sleevetogether. A solid 1.3 cm (0.5 in.) rod is welded tothis insert and extends through and above thehollow drill rod where it is clamped to astationary rod fastened to the gear housing. Thesolid rod sections are connected with left-handthreaded couplings to prevent unscrewing. Thisarrangement keeps the sample tube from turn-ing-as the outside auger tube is rotated.Seven sample holes, from 3 to 5 m deep, wereFu;. 2. Installing the split sleeve and split sleeveholder in preparation for sampling.FIG. 3. A simplified view of the proper alignmentof sampler components.drilled. Bedrock in the soils sampled was ap-proximately 5 m (15 to 16 ft) below the soilsurface. A very hard, compacted layer encoun-tered between 25 and 100 cm was sampledeasily. The undistrubed cores were taken in61-cm increments, and cores were obtained tothe 5-m depth in about 8 hr. This time includessetting up for sampling, sampling, and prepar-ing and storing samples. This time would vary,depending on soil type and water content. Wesampled very dry soils and sampling probablytook longer than would be necessary for soilswith ideal water content. All samples wererecovered, even in the very dry moisture range.The greatest difficulty was encountered whiletrying to store the samples where moisturecontent was below 6 percent moisture byweight. There was no measurable compaction ordistortion of samples.The samples collected in this study wereimmediately placed in 5-cm-diameter shrinka-ble tubing. The tubing prevents damage to thecores while transporting or storing, and can alsobe shrunk around the sample by heating to formCORE SAMPLER	 155a watertight container for hydraulic conductiv-ity and other flow studies. The dimensions ofthe sampler and the power unit described in thisnote are optional. If sampling to greater depthsis necessary, it would be advisable to use alarger power unit. Also, difficulty could beencountered in sampling very dry or gravellysoils.REFERENCESHayden, C. W. and W. H. Heineman, Jr. 1968. Ahand-operated undisturbed core sampler. SoilSci. 106: 153-156.

Mechanical Snake River Undisturbed Soil Core Sampler

Northwest Irrigation & Soils Research Laboratory Publications

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Mechanical Snake River Undisturbed Soil Core Sampler

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