Estimation of Water Content Curve Using Soil Properties Analysis Data

394 Estimation of Water Content Curve Using Soil Properties Analysis Data Muhannd Waleed Majeed1, Lubna Mohammed Abd2*, Mohammed Nsaif Abbas3 1 Lecturer, Water Resources Engineering Department, College of Engineering / Mustansiriyah University, Baghdad, IRAQ *2Assistant Lecturer, Environmental Engineering Department, College of Engineering / Mustansiriyah University, Baghdad, IRAQ 3 Assistant Professor Doctor, Environmental Engineering Department, College of Engineering / Mustansiriyah University, Baghdad, IRAQ ABSTRACT

D 2216). ASTM method D-2216 which determines, the free water or pore water, content as a percentage based on moist and oven dried, soil weight differences may generate, erroneous, information for soils with a high organic, material content. The BS 1377 - 2: 1990 also states, that a microwave oven should not be used as definitive, method in determining the moisture content of soils containing organic matter such as peat. This is caused, by the difficulty in ensuring, temperature of soil does, not exceeds 110°C. However, peat, soil samples may experience particle burning even at temperatures well below 110 °C. Another, factor of importance is the method, of sampling by boring, which may affect the measurement, of field moisture content. This is because, once a sample is taken at the particular point, the soil, has been disturbed and its, properties may be altered. This introduces, another variable, the heterogeneity, of the soil, into the moisture measurements; also there may, be internal migration, of water or moisture loss during sampling. The loss of moisture due to free draining during removal of the sample from the borehole, also may be of importance. As a result, of the above, factors that will significantly affect the determination of moisture content of fibrous peat must be identified. The use, of present testing techniques, for peat, moisture is unsatisfactory, and therefore it is necessary, to establish more, reliable methods for obtaining the moisture, content of fibrous, peat in the field [4] .
Soil moisture, can also vary, in response to other factors, including bulk density, organic matter, and proportions, of sand, silt, and clay. An indicator, variable, soil water capacity, was determined, at each sample point to account, for these undetermined properties. This approach is similar to that of Helvey et al. (1972) [5] , who, determined, a factor to "remove the relatively unaccountable variation in moisture content resulting from the soils' ability, to retain water against drainage, and evapotranspiration." This variable, which I call "soil water capacity", is the amount of moisture, in the soil when, it is wetted to near, field, capacity.

Soil moisture content
The soil moisture content, indicates, the amount of water, present, in the soil. It is commonly, expressed, as the amount of water (in mm of water depth) present, in a depth, of one meter of soil. For example: when, an amount of water, (in mm of water depth) of 150 mm is present, in a depth, of one meter of soil, the soil, moisture content, is 150 mm/m, see fig.1. Sandy, soils specially, the loose, one have low, resistance to applied, loads caused by buildings [7] .
The soil, used in this study, is a fine to medium, poor graded gray sand, brought from Abo-Nooass reign in    [8] .
The behavior, of clayey soil, is complex comparing, to the cohesionless soils, in addition saturated clays are generally, weaker than sand or gravels and thus are more to cause a problem. The clay, particles undergo greater volume change during loading, the low, permeability, impedes the flow of water into the voids and the undrained, condition applied, in short term and significant, excess pore water pressure will develop in this soil.
In long term, water does, flow into or out the soil, allowing, the excess pore water pressure generated, during loading to dissipate, virtually completely, and the drained condition,, applied [9] .
The soil used, in this paper is brought, from Al-Tagy region, to the north, of Baghdad. Standard tests, were performed to determine, the physical properties, of the soil which is brown as shown in fig. 4 and table 2.  Swelling, of soils occur in partially, saturated plastic soils exposed, to wetting during raining, seasons or due to leakage, of water pipes or rise of water table through the expansive soil layer. A measure, of the ability and degree to which a soil might swell when, its environment, is to be changed is known, as swell, potential, the free swell is defined, as the percent of increase, in volume of partially, saturated sample of soil when exposed, to wetting [10] .
The clayey, soil used in this study, is a natural, soil   Alphen and Romero [11] reported that gypseous soils refer, to soil containing, more than 2% gypsum, while Barazanji [12] distinguished, classes of gypsiferous soils based on the gypsum, content as shown in Table4. A soil can be defined as a gypseous soil when, the gypsum content suffices to change the properties of the soil. The Russian system of gypseous soil classification, in Table 4 relies upon, the upper limit of the gypsic horizon, the content, of gypsum, the thickness, of the gypsic horizon, and the measure, of gypsiferous accumulation [13] . Table 4. Classification of Gypseous Soil [12] Gypsum content %    5. Distribute, the blows uniformly, on each layer.
6. The amount of soil used shall be sufficient, to fill, the mould leaving, not more than about, ,6mm to be struck, off when the extension is removed.    8. As the % of fines, and the plasticity of a soil, increases, the compaction curve becomes, flatter and therefore less sensitive, to moisture, content.
Equally, the maximum, dry density, will be relatively, low.
9. Gypsum soils usually stiff when they are dry, but these soils may affected greatly, when subjected, to changes, in water, content due to water table fluctuation or due, to water, infiltration, which may dissolve, gypsum causing pores and cracks.
10. The maximum, dry density in gypsum, soils occur at the lowest optimum water content as compared with the, remain soil types.