In order to estabilish a method of estimating the long term settlement of highty organic soil overconsolidated by preloading, a series of laboratory and field measurements were carried out. Observation of ground movement during preloading and unloading indicate that primary settlement occurs first and then unloading makes the ground swell. Afterwards, secondary settlement occurs with a liner relationship between settlement and the logarithm of time.
Based on these findings, a method of estimating the amount of swelling and secondary settlement was established empirically for practical use. The proposed formulas make use of overconsolidation ratio, water content, duration of loading, and soil data (initial pore ratio, thickness of settlement layer, etc).