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• coarse gravel: 19 - 75 mm; • fine gravel: 4.75 - 19 mm; • coarse sand: 2.0 - 4.75 mm; • medium sand: 0.425 - 2.0 mm; • fine sand: 0.075 - 0.425 mm; • silt: 0.002 - 0.075 mm; or • clay: <0.002 mm. 3.4.5 Plasticity Plasticity is the property of sediment that allows it to deform in a fluid-like manner when stressed. Plasticity is divided in the USCS classification as high plasticity (H) or low plasticity (L). Only fine grained sediments demonstrate plasticity, with clays generally being more plastic than silts. Plasticity is best measured through laboratory testing of sediment Atterberg Limits. However,the following are several useful tests for estimating plasticity in the field: • Dry strength test — Water is added to a pat of soil until it is the consistency of putty and can be formed into a cube of approximately '/2-cubic inch. The soil will be allowed to dry completely in the sun. The dry strength is estimated by the difficulty of breaking the dried cube of sediment. Dry strength increases with plasticity, therefore highly plastic sediment(clay) will be more difficult to break, and less plastic sediment (silt and fine sands) will be less difficult to break. • Dilatancy test— Water is added to a pat of soil until it is the consistency of putty and is about '/2-cubic inch in volume. Place the sediment in the open palm of the hand and shake horizontally,tapping fingers of the other hand on to the palm next to the sediment. The appearance or lack of water on the surface, and the speed of the reaction should be noted. Next, squeeze the sediment and observe if this causes the water to disappear from the surface and the sample to stiffen and eventually crack or crumble. The rapidity of the appearance of water on the surface during shaking and disappearance of water while squeezing indicates low plasticity, while water will not rise to the surface of high plasticity sediment. • Toughness test—Water is added to a pat of soil until it is the consistency of putty and is about '/2-cubic inch in volume. The sample is rolled in the palm so that it forms a thread and is rolled until it falls apart. If the thread is less than 1/8-inch 9