數量極為有限的實驗室數據顯示，飽和土壤的單向度壓密超額孔隙水壓力於二次壓縮開始時可能不為0，這與Terzaghi單向度壓密理論所描述的並不一致而令人驚訝。本研究旨在評估二次壓縮開始時的超額孔隙水壓力大小以及隨後的依時消散情形，從實驗室單向度壓密試驗所得數據顯示，兩種天然黏土試樣底部之超額孔隙水壓力於Casagrande主要壓密完成時間時仍大於0，且隨時間持續消散至大約10倍主要壓密完成時間時才等於0。當壓密曲線未具有典型之S形時，建議可依超額孔隙水壓力之大小來決定主要壓密完成時間。

It is shown from very limited amount of laboratory data that the excess pore water pressure of saturated soils during one-dimensional consolidation may not be zero at the beginning of secondary compression. This is surprising because it is inconsistent with what is described in the Terzaghi’s theory of one-dimensional consolidation. This study aims at an evaluation of the magnitude of excess pore water pressure both at the beginning and during secondary compression. Data obtained from laboratory oedometer tests show that the excess pore water pressure at the bottom of the specimens of two natural clays at the time of Casagrande EOP consolidation is still greater than zero, and it continues to dissipate before reaching zero at a time about 10 times the time of EOP. When the one-dimensional consolidation curve is not of the typical S-shape, it is recommended that the time of EOP may be determined based on the magnitude of the excess pore water pressure.