TAILIEUCHUNG - Encyclopedia of Global Resources part 119

Encyclopedia of Global Resources part 119 provides a wide variety of perspectives on both traditional and more recent views of Earth's resources. It serves as a bridge connecting the domains of resource exploitation, environmentalism, geology, and biology, and it explains their interrelationships in terms that students and other nonspecialists can understand. The articles in this set are extremely diverse, with articles covering soil, fisheries, forests, aluminum, the Industrial Revolution, the . Department of the Interior, the hydrologic cycle, glass, and placer mineral deposits. . | 1108 Soil testing and analysis Global Resources Physical Testing and Analysis Physical testing investigates the physical properties and behavior of soils. The most fundamental level of physical testing includes estimation of specific gravity determination of moisture content sieve analysis and hydrometer analysis. Specific gravity is defined as the ratio of unit weight of soil solids only to unit weight of water. For sandy soils the specific gravity ranges from to while for clays it is between and . The specific gravity of organic soils is less than . Moisture content is defined as the ratio of the weight of water present in a soil sample to the weight of dry soil. Moisture content is about 15 to 20 percent for coarse soils and 80 to 100 percent for clays. Organic soils may have moisture content in excess of 500 percent. In order to determine the grain-size distribution of coarse soils the soil sample is subjected to sieve analysis. This analysis is conducted by using a stack of sieves that have a decreasing sieve diameter from the top to the bottom. The sieves are usually made of woven wires. After the sieves are shaken for a specified period of time the amount of sediment retained at each sieve is weighted. Based on these data each particle diameter is plotted in terms of the percentage of material that is finer than this particular diameter. For the plot a semilogarithmic paper is used. For the determination of particle size distribution of fine soils the hydrometer analysis is applied. The lower limit of the particle diameter that can be detected by this analysis is millimeter. The hydrometer measures the particle diameter indirectly. This analysis is based on the principle that the hydrometer will be subject to higher buoyancy forces in a well-mixed water-sediment system. However as the suspended solid particles settle the density of the water-sediment mixture decreases and the hydrometer tends to sink. The grain-size distribution .

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