A phenomenon is found that the pore water pressure in the soil specimen inclines to delay during the single-drainage consolidation test by using the oedometer which can measure the pore water pressure at the bottom of specimen. In order to analyze its cause

a one-dimensional dynamic consolidation equation in which the vertical strain is set as its dependent variable is presented to take into account of the dynamic effect due to instantaneous loading

and the numerical analysis is performed by using the finite difference method. A new parameter CD composed of the modulus of compressibility

coefficient of permeability

density and thickness of specimen is introduced to characterize the dynamic effect; and then its influence on the pore water pressure in the process of consolidation is investigated. The numerical results indicate that the dynamic effect due to loading is a cause of delay of pore water pressure in the specimen

and the phenomenon is easier to appear for the soil specimen with greater modulus of compressibility or coefficient of permeability. In addition

the dynamic effect has a certain influence on the consolidation degree in the early period of consolidation. Finally

the consolidation cases are discussed that the dynamic effect can be negligible.