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Western Dam Engineering <br /> Technical Note <br /> <br /> <br />6 <br />provides a good reference for this type of information. <br />Table 1 below also summarizes testing methods and <br />associated design considerations for various index <br />properties. <br />Different sample types, volumes, and preparation <br />methods are required for different types of laboratory <br />tests. For example, most index property tests can be <br />performed using disturbed samples (commonly <br />obtained using split spoon or modified California <br />samplers, or by hand from an auger flight, spoil pile or <br />test pit). Conversely, if testing of in-situ properties is <br />desired, engineering property testing such as triaxial <br />shear strength, consolidation, collapse, and <br />permeability tests require relatively undisturbed <br />samples, such as obtained from thin-walled samplers. <br />There are exceptions; for example, strength or <br />permeability tests are often performed on remolded <br />samples to enable modeling compacted embankment <br />fill. <br /> <br />Care should be taken to avoid sample disturbance <br />when handling and transporting samples intended for <br />in-situ properties testing from the field to the <br />laboratory. Sample disturbance can significantly affect <br />test results, possibly resulting in mis-characterization <br />of a soil, especially for loose or weaker soils. <br />Laboratory tests, along with the results of field <br />observation and testing, can also be used to identify <br />the properties of special or problematic soils or <br />adverse ground conditions. These can include <br />collapsible soils, dispersive soils, organic soils and peat, <br />expansive soils, slaking shales and degradable soils, <br />sensitive clays, and ground susceptible to fissures. <br />Soil Classification & Description <br />Soil classification is the grouping of a soil into a <br />category, typically using an established system such as <br />the USCS. Soil description is the systematic, precise, <br />and complete naming of individual soils. The soil’s <br />classification and description, as typically provided on <br />a test hole log, should include as a minimum: <br /> Apparent consistency (stiffness for fine- <br />grained soils or density for coarse-grained <br />soils) <br /> Water content condition adjective (e.g., dry, <br />moist, wet, saturated) <br /> Color (e.g., red color can indicate weathered <br />soil, green can indicate organic content) <br /> Plasticity adjective for cohesive soils (e.g., <br />medium plasticity) <br /> Minor and MAIN (capitalized) soil types (e.g., <br />clayey GRAVEL [GC]) <br /> USCS Group name and symbol (e.g., GC, GM, <br />GW, GP, SC, SM, SW, SP, ML, CL, SP-SM, etc.) <br /> Inclusions (e.g., trace amounts of other soil <br />types, organic content) <br /> Geologic name, or embankment zone, if <br />known <br />Field engineer’s or geologists make their best <br />determination of the soil classification at the time of <br />drilling and sampling. Final boring or test pit logs are <br />typically checked and adjustments made as necessary <br />based on the results of the laboratory testing. Here is <br />a typical example of a soil description that may be <br />found on a test hole log: <br />“medium-dense, moist, red-brown, silty SAND <br />(SM), trace fine gravel to coarse sand <br />(Alluvium)” <br />Soil descriptions should be provided for each main <br />strata or zone of soil identified in the foundation and <br />embankment. Standard methodology for visual soil <br />classification is provided in ASTM D 2488 – Standard <br />Practice for Description and Identification of Soils <br /> <br /> <br />Assortment of soil testing equipment: (a) Atterberg Limits, <br />(b) Sieve Analysis, (c) Consolidation, (d) Triaxial Shear <br />a b <br />c d