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Western Dam Engineering <br />Technical Note <br />3 <br />identified. The investigation plan might also include <br />phone numbers to communicate events, written <br />procedures to help promptly deal with unusual conditions <br />or damage, and guidelines for the work associated with <br />the drilling and sampling. <br />Typical Sampling Methods <br />Appropriate sampling methods vary based on the target <br />strata being investigated. This is a general summary of <br />typical methods for obtaining samples to characterize <br />embankment dam materials. Refer to the referenced <br />ASTM standard for detailed information on each sampling <br />type and method. <br />Photo 1.Example Samplers (Photo Courtesy of CME) <br />Split spoon sampling using Standard Penetration Test <br />procedures (SPT) (ASTM D1586): A split spoon sample is a <br />driven-sample generally obtained using the SPT method. <br />This provides both an in situ test of the relative <br />consistency (density/stiffness) of the material and obtains <br />a disturbed sample. Split spoon samples can be <br />performed in most soil types and weak rock, but are not <br />appropriate for strong rock. If the material is non- <br />cohesive (sandy), then various catchers may be used at <br />the sampler tip to help retain the sample; however, these <br />may affect SPT results is low strength material. The <br />resulting sample is appropriate for index testing <br />(gradation, plasticity, moisture content, etc.). Samples <br />should be removed from the sampler and placed in <br />sealed plastic baggies to retain moisture. (Laboratory <br />testing of samples will be discussed in a subsequent <br />issue.) <br />Thick-walled split tube sampling (i.e., modified California <br />sampler, ASTM D3550): is a driven-sampling method <br />using a ring-lined barrel that provides a slightly less <br />disturbed sample of soils and weak rock, but is not <br />appropriate for strong rock. This sampling method is also <br />often used following SPT procedures. It is preferred over <br />the split spoon when a less disturbed sample is desired <br />and the material has sufficient cohesion to be retained in <br />the sampler. The ring sample should be carefully sealed <br />with wax or taped plastic caps. The ring samples can best <br />be used for index property characterization (gradation, <br />plasticity, moisture content, etc.). Use caution performing <br />tests on these samples, when they are intended to <br />represent in-place properties such as density and <br />strength, as some disturbance of the soil likely occurred. <br />Thin-walled sampling (i.e., Shelby tube, ASTM D1587): <br />Shelby tube sampling is a push-sample method that <br />provides a relatively undisturbed sample of fine-grained, <br />cohesive material. It may be difficult for sampling non- <br />cohesive or granular material such as sands or gravels, as <br />they are difficult to retain in the tube, although special <br />procedures have been developed for thin walled <br />sampling of sands using fixed piston samples, which <br />provide for development of vacuum in the soil pores <br />during sample extraction. Tube sampling of sands <br />requires great skill and care and special precautions must <br />be taken to limit disturbance of these samples during <br />transportation. Quality Shelby tube samples are <br />appropriate for testing index properties as well as in- <br />place characteristics such as density, consolidation, and <br />strength properties, as this method generally results in <br />the least disturbance of soil sampling when performed <br />properly. Samples should be retained within the tube to <br />allow the laboratory to carefully extrude the sample. <br />Sample disturbance and change in sample condition is <br />likely if the sample is extruded in the field. The tube <br />should be carefully sealed with wax or o-ring packers. <br />Care should be taken to avoid sample disturbance during <br />transportation to the laboratory, especially for soft soil <br />samples. <br />Core sample: A “core” sample refers to a relatively <br />continuous sample recovery of the drilled material. Core <br />samples are obtained through the drilling process itself. <br />Sample cores can be relatively undisturbed or disturbed <br />based on the drilling method used. Core samples can be <br />obtained using diamond coring, sonic drilling, and even <br />auger drilling when a plastic-lined auger string is utilized. <br />Undisturbed core samples are appropriate for testing <br />index properties as well as in-place properties such as <br />Split Spoon <br />Shelby <br />Tubes California Tube <br />Sampler