VARIATION OF BEARING CAPACITY PREDICTION FOR SHALLOW FOUNDATIONS BY SPT AND LABORATORY TESTS

Abstract

This study presents the results of the bearing capacity variation for the shallow foundation from field tests (SPT test) and laboratory tests. Site investigation and geotechnical evaluation for soils Nasiriyah, Iraq. The main purpose of this study is to determine the surface and subsurface conditions with the physical, mechanical and chemical properties of the encountered materials in order to provide recommendations for design and construction of the proposed project foundations. Two types of samples were taken (disturbed and undisturbed samples) for laboratory testing. Laboratory tests were performed on the recovered samples in order to identify the physical, mechanical and chemical properties of the encountered materials. Classification and index tests: moisture content, Atterberg limits, particle size distribution, and specific gravity are carried out to classify the soils. Strength tests: Triaxial (Unconsolidated Undrained UU) and unconfined compression strength (UCS) test to evaluate the cohesion of the soil, c. In addition, chemical tests: pH, sulfate, chloride, TDS, EC and organic matter are carried out. The results showed that the measured bearing capacity depending on the UCS test and Triaxial UU tests data is more reliable than the measured bearing capacity depending on the SPT test date. The estimated value for cohesion, c by eq.2 is very high and does not represent the actual value especially in clayey soils. The increase in fine material (clay and silt) content decreases the N value. While the increase in the course material (sand and gravel) content increases the N value. Moreover, the increase in the soil sample water content decreases the N value.