Classifying soils into groups with similar behaviour, in terms of simple indices provide a general guidance about engineering properties of the soils. Complemetary physical properties of soil mean any three properties of soil that any two of them will be enough to estimate the third one, for examples Atterberg limits (Liquid Limit %, Plastic Limit % and Plasticity Index %) are substantially complementary physical properties due to the equational relationships between these three properties. Also the size fractions of soil that component from three fractions only (Clay %, Silt % and Sand %) are complementary physical properties because the total sum of these properties will be handred percent. In this study only two of the three complementary physical properties of soil have been converted to standardized values by subtracting each properties from the mean value and dividing the result by the standard deviation . The standardized values values are plotted on two dimensional graph which divided into a uniform area up on the unity standard deviation. Number of samples are measured in each area to draw the contours map which shows the individual groups . this a simple statistical treatment for a complementary physical properties of soils has been applied on soil data from Tulool Al-Bacth/Shirqat road. The resuls shows very satisfactory.

In hydrometer analysis for soil grain size distribution, usually, the grains passing sieve No. 200 (<0.074 mm) are used. However, the hydrometer results occasionally give diameters greater than 0.074 mm. This event causes a mismatch in the curve of grain size distribution obtained from sieving and hydrometer methods. Hence, a new approach is proposed for smoothing soil grain size curve determined by hydrometer using Excel-2007 with simple statistical methods. The treatments show that in case of large sizes, there are big differences between the values of soil grain diameters smoothed by Excel-2007 in comparison and the values measured by references. These differences generally decrease with decreasing soil grain size diameters. The statistical treatments also divulge whether the hydrometer results are accurate or not. Furthermore, a general equation has been derived to estimate values of K factor, which is used for calculating the grain diameters in hydrometer analysis. The equation can be applied for any specific gravity of soils and for wide range temperatures.