Abstract: The behaviour of the saturated soft clay nearby the tunnel of a certain section of Shanghai Metro Line 2 was investigated.Under the action of the vibration loading of the subway,the embedded piezometer continuously monitored the vibration frequency in the soil at different locations and different depths.The corresponding influence of the vibration loading to the pore water pressure inside the saturated soft clay was studied.Then the accumulation and dissipation of the pore water pressure inside the saturated soft clay were also observed.Furthermore,its mechanism was analyzed by use of soil dynamics and the principle of energy loss.