Contents 5 Soil classification

The density of the soil in its undisturbed state depends on various factors, the main factors being the soil classification group, the moisture content and the degree of natural compaction. Indicatively, in situ soil density values vary from 1200 to 1700 kg/m for loose soils and 1500 to 2200 kg/m for dense soils. 

The precise determination of the representative moisture content of the subgrade during the pavement s service life is a difficult, if not impossible, task. This is because the subgrade moisture content during the pavement s service life is affected by various factors, the most important of which are the seasonal variation of the depth of the water table level, the type of soil material (soil classification), the construction conditions in terms of provision of drainage system and the thickness of superimposed layers (thickness of pavement). 

Designing a protective system is complex because of the nmnber of factors involved — soil classification, depth of cut, water content of soil, changes due to weather and climate, or other operations in the vicinity. The OSHA regulations, however, provides several different methods and approaches. Protective systems must be able to resist, without failure, all loads that are intended or could reasonably be expected to be applied or transmitted to the system. 

Designing a protective system can be complex because of the number of factors involved-soil classification, depth of cut, water content of soil, changes due to weather and climate, or other operations in the vicinity. 

Soil classification particle grain size distribution, hydrometer, Atterberg limits, field identification tests, linear shrinkage and moisture content test ... 

Clay, in one particle classification system, consists of inorganic particles less than 0.005 mm in size. In another system, clay is a fine-grained inorganic. soil that can be made plastic by adjusting the water content. When dried, clay exhibits considerable strength (i.e., clay loses its plasticity when dried and its strength when wetted). Also, it will shrink when dried and expand when moisture is added. 

Charette, M. P., McCord, T. B., Pieters, C. Adams, J. B. (1974) Application of remote spectral reflectance measurements to lunar geology classification and determination of titanium content of lunar soils. J. Geophys. Res., 79,1605-13. 

Table 11.1 Variability in organic carbon content for the soil units (stone free soil) of the Brazilian classification. ...

Table 3 compares the most commonly used peat classification systems based primarily on degree of decomposition. The U.S. system (Soil Taxonomy, USDA, 1975) and the Canadian system (Day, 1968) are essentially similar except for terminology and are based on the amount of unrubbed or rubbed fiber content. 

Figure 3.1 shows typically that for any soil as the compactive effort increases, the maximum density increases and the optimum water content decreases. The approximate relative moisture density relationships for the soil designations of the Unified Classification System are shown in Figure 3.2. 

The mobility of Mn defies classification because it is extremely sensitive to soil conditions (acidity, wetness, biological activity, etc.). Toxicity to plants is most likely in waterlogged soils or acid soils with low humus content. Deficiency is most often found in soils that are saUne and alkaline, calcareous, peaty, coarse textured, or acid leached. 

Hvorslev (1949) classified soil samples as nonrepresentative, representative, or undisturbed. This classification is made by comparing the state of the sampled soil to that as exists in situ. A nonrepresentative sample is one in which soils from different strata have been mixed, or some of the soil constituents of the sampled soil are missing. Samples that contain scrapings from the well of the borehole or samples with some of the fine particles washed out during sampling fall in this category. A representative soil sample is one in which there is no change in soil constituents but whose structure, water content, or void ratio has been altered. An xmdisturbed sample, ideally, is one that represents the in situ condition. 

Soil characteristics most used in engineering classification systems are particle size and consistency (Atterberg limits). These simple tests reflect the soil s physical properties, composition, moisture content, and so on. The information obtained by these tests enables an individual to assess the quality of a soil for construction or as a foundation. Several systems are in use in the United States and throughout the world, which have application in the... 

Because the period of pesticide stability in water and soil depends on many different factors (e.g., variations in pH of water and soil, bacterial content, plant and animal content, temperature, humidity, and degree of solar radiation), this classification is largely conventional. It does, however, permit the definition of many organochlorine pesticides (DDT, hexachlorocycyclohexane, aldrin, diel-drin, heptachlor and others) as very persistent (Table 1). 

The soil texture types mainly are sand and loamy sand according to American soil texture classification, the ranges of sand, silt and clay contents are 74.08% 99.6%, 0.40% 23.52%, 0 2.4% (Table 1), sand content is far higher than silt and clay, and clay is the lowest, therefore, soil samples are assumed coarse textured. Silt and Clay have a strong variation with the variation coefficients are larger than 75%, while BD and Sand have a weak variation. Bulk density ranges from 1.35 to 1.76 g/cm, possibly for reason that soil sand content is very high. The 120 measured soil water... 

Atterberg (liquid and plastic) limit tests on cohesive soils for classification and correlation studies. Significant insight relative to strength and compressibility properties can be inferred from the natural water content and Atterberg limit test results. 

Soil varies widely from place to place. As a matter of fact, soil scientists have set up classification systems in which soil is considered to be composed of a large number of individual soils. The term soil is a collective term for all the soils just as vegetation is used to designate all plants [11]. The soil environment is affected by several uncontrolled parameters. The temperature (which is dependent on the regional climate and the seasonal fluctuations), the soil water content [dependent on rainfall (a climatic factor) and irrigation... 

The pulverized coal ashes used in this stndy were obtained from Dutch and Danish coal fired installations. According to an earlier proposed classification acidic, neutral and alkaline reacting ashes were selected for specific purposes [1]. Some of the data presented in this paper refer to ashes collected in an earlier study on the classification of coal ashes [13]. The soil samples—clay, sand and peat— were collected from the C— horizon in the Netherlands by STIBOKA, Wageningen. More detailed information on the sample origin and properties is given in ref [14]. In this paper only data relevant to molybdenum behaviour will be presented. In table I the molybdenum content of the... 

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