Tests of interface between compacted clay and concrete were conducted systematically using interface simple shear test apparatus. The samples, having same dry density with different water content ratio, were prepared. Two types of concrete with different surface roughness, i. e., relatively smooth and relatively rough surface roughness, were also prepared. The main objectives of this paper are to show the effect of water content, normal stress and rough surface on the shear stress-shear displacement relationship of clay-concrete interface. The following were concluded in this study: 1) the interface shear sliding dominates the interface shear displacement behavior for both cases of relatively rough and smooth concrete surface except when the clay water content is greater than 16% for the case of rough concrete surface where the shear failure occurs in the body of the clay sample; 2) the results of interface shear strength obtained by direct shear test were different from that of simple shear test for the case of rough concrete surface; 3) two types of interface failure mechanism may change each other with different water content ratio; 4) the interface shear strength increases with increasing water content ratio especially for the case of clay-rough concrete surface interface.

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in geotechnical engineering, foundation piles are ideal for deep foundations that cannot bear higher loads. This architectural expansion places a great deal of responsibility on the engineer to anticipate the appropriate load for the constructor. Unfortunately, calculations of the pile’s bearing capacity are not accessible. It has always been a source of concern for geotechnical engineers, as the structure’s safety depends on the pile’s bearing capacity and gives it a safe value. These research tests are previously known pile load test data from several locations in Nasiriyah to determine the ultimate load-carrying capacity using various interpreting methodologies. A database that was used to test the pile load for three different areas in Nasiriyah, southern Iraq: The Main Drain River Bridge Project, the Al-Eskan Interchange Project, and the Al-Hawra Hospital, as determined by analytical methods, as well as evaluating the final loading values resulting from the methods used, by ASTM D-1143, American and British Standard Code of Practice BS 800. The final capacity for the pile bearing is estimated using these approaches, which are depicted in the form of a graph-based on field data. Chin-Kondner and Brinch Hansen algorithms anticipate the highest failure load for all piles based on the comparison. On average, Chin–Kondner’s ultimate load is 22% higher than Hansen’s maximum load for the 22 pile load tests. Decourt and DeBeer, and Mazurkiewicz’s techniques yielded the closest average failure load. Buttler-Hoy approach yielded the smallest failure load.

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In many cases, the soil in Nasseriyah, Iraq, is not suitable to support the shallow foundations of low to medium rise buildings without improvement or replacing the founded layer with a strong layer. Therefore, the reinforcement method as one of many types of improvement methods may be used to increase the bearing capacity and reduce the settlement when the replacement soil is not enough to support the foundation. This paper reviews the most important reinforcement materials such as geogrid that may be used to increase the strength of the soil and other details of the number of layers, the distance between layers and the optimum location of the top reinforced layer for clay and sand soil. Experimental studies and theoretical modelling performed through the last decades are reviewed to choose the best arrangement of geogrid material that gives the best performance when it is used with soil. It is found that the geogrid can be used to increase the bearing capacity, however, the studies on clay reinforced with geogrid compared to sand soil are few. Since the researches on the behavior of foundation resting on clay reinforced with geogrid are few and because the soil in Nasseriyah is mostly clay soil, it is recommended to study the behavior of foundation resting on clay reinforced soil.