Investigation of Relationship between Distortion Settlement, Lateral Spreading and Consolidation Settlement of a Selected Cohesive Soil

Long-term settlement of foundation on clay soils is a well-known aspect of geotechnical design. Prediction of the performance of building foundations or embankments can be complicated and expensive in such ground conditions. Construction costs need to be balanced against high maintenance costs considering the long term performance. In order to do this optimally, there is a need to predict long term settlement with reasonable accuracy. For a reasonable prediction of long term settlement, it is crucial that ground investigation, laboratory testing and monitoring of ground settlement during and after construction are carried out. However, in most cases these are not possible to carry out in a project due to various reasons such as; increased construction costs, time and resource limitations etc. Hence, engineers commonly rely on punished empirical data on ground settlement behavior, which may sometimes be misleading. In order to reduce the cost of obtaining a reasonable prediction of long term settlement, it is proposed that the existence of a relationship between short term or immediate settlement and long term settlement is investigated. Immediate settlement of shallow foundations bearing on clay soils may constitute a significant part of the total settlement. Immediate settlement occurs due to the distortion of cohesive soils in untrained condition also defined as constant volume deformation. As part of this research, two basic mechanisms will be considered; 1- one dimensional consolidation settlement behavior (K=1 loading, in drained condition), and 2- one dimensional distortion settlement behavior (K= variable but controlled, in untrained condition). Two main goal were considered on the settlement behavior investigated using iv compacted specimens; the immediate settlement behavior and assessment of the relationship between the immediate settlement, consolidation settlement and the total settlement. For the Investigation of one dimensional distortion settlement behavior, a new testing equipment and testing methodology were designed. Experimental findings showed that as the confining stress increases, the immediate settlement indicates descending trend. It was concluded that the ratio of immediate settlement to long term settlement reduces as the value of confining stress increases. The results of this research are in good agreement with those in the literature on the ratio of immediate settlement to long term settlement. Keywords: consolidation settlement, cohesive soil, immediate settlement, lateral spreading