Abstract: “The magnitude of preconsolidation pressure plays important role in civil engineering practice. Effect of preconsolidation should be considered in settlement and stability problems. In this study laboratory tests have been conducted in order to investigate the preconsolidation pressure of Irbid clay. Several methods have been employed to investigate the range of preconsolidation pressure. Laboratory tests have indicated that Irbid clays are overconsolidated due desiccation. This conclusion has been reached because overconsolidation ratio decreased with depth until it becomes one at certain depth; this means that only the top layers are overconsolidated which can be due only to desiccation. Also, it was concluded that the most convenient method to determine the preconsolidation pressure of Irbid clay is Casagrande method as compared with other examined methods.”

Keywords: preconsolidation pressure, Casagrande method, Schmertmann method, minmum possibe presconsolidation pressur