Stiffness of soil that is defined as ratio of load to deflection depends on some physical properties such as compactness and water content. The purpose of this research study is to use stiffness for estimating compactness of granular geomaterials that are used as subbase and base courses of roads. In this research study, the stiffness of soil samples was determined according ASTM D6758-08 test method by using electro-mechanical device. The dry density of the compacted soil was determined by sand-cone method in the field. More than 80 laboratory and in situ tests were performed. The obtained stiffness data was used to establish a relationship between stiffness, compaction ratio and water content. The results showed that there is a strong relationship between the stiffness, compaction ratio and water content. Also, the result of validation showed that there is good correlation between in situ and laboratory tests results.

The behavior of the Siah-Bisheh concrete face rock-fill dam in Mazandaran, Iran was investigated. Numerical analyses were performed before construction to evaluate the stability and predict the deformation of the dam. The material properties were chosen based on the results of geotechnical investigations. The amounts for deformation and settlement of the concrete surface were also calculated with the numerical model. The information from a number of geotechnical instruments was collected after construction and analyzed to measure settlement at different sections of the dam. The locations of the different deformations and their values are presented with various contours. The data were analyzed and used to revise the original numerical model of the dam. Following that, the long-term stability of the dam was evaluated, using parameters that were modified based on the measurement data. A comparison of the results from the numerical analysis and the values obtained from the dam settlement measurement showed that the initial results from the numerical model were much higher than the real values. It also showed that the number of construction layers used in the modeling of the dam had a significant effect on the obtained maximum amount of deformation.

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