Time effect of the pile bearing capacity in dredger fill

摘要

The dissipating of pore water pressure caused by pile sinking is one of the main factors resulting in time effect of ultimate bearing capacity of pile. The pore water pressure is monitored at each observing point during pile sinking and after that. With the pore pressure plan embedded in advance, by means of spot test in the process of pile sinking, under this geological conditions of the pile foundation by referring to the second phase project of the free port logistics processing zone in Dongjiang, Tianjin. The change law of the distribution and dissipation of excess pore water pressure with time, depth, radial distance and permeability coefficient of soil was also discussed. It's found that the excess pore water pressure attenuates approximately linearly with the increase of the distance from the pile heart and the scope influenced is around 10 d. As the numerical simulation accord with the test results effectively, promote the results then get the change rule of pile bearing capacity with time. The formula of pile bearing capacity about time effect in dredge fill was deduced for engineering reference. The effect of soil internal friction angle on the ultimate bearing capacity of pile was discussed. Numerical simulation shows that the ultimate bearing capacity of pipe pile increases over time and keeps stable after 20 d. The ultimate limit bearing capacity is 1473 kN with increase of 12.3%, the time when it reaches the stable state is in accord with the excess pore water pressure dissipation monitored at each observing point. The larger the internal frictional angle of soil becomes, the more the ultimate bearing capacity is. The angle exceeding 20°, the bearing capacity would not increase as internal frictional angle of soil increases.