This document discusses preconsolidation pressure in soils. It defines preconsolidation pressure as the maximum effective vertical overburden stress a soil sample has experienced in the past. Though it cannot be directly measured, it can be estimated using methods like analyzing the curvature of a consolidation curve. A soil is considered normally consolidated if the current vertical effective stress is equal to or greater than the preconsolidation pressure. The document also lists factors that can cause a soil to approach its preconsolidation pressure, such as changes in total stress, pore water pressure, soil structure, or environmental conditions. Finally, it states that knowing the preconsolidation pressure is important for predicting settlement, site preparation for construction, and determining appropriate