CONSOLIDATION BY VERTICAL DRAINS TAKING WELL RESISTANCE AND SMEAR INTO CONSIDERATION

ABSTRACT A rigorous solution for the consolidation of soil by displacement-type vertical drains with finite permeability is presented taking into account the disturbance in a clay ring surrounding the drain pile caused by drain installation. The accuracy of both Barron’s and Hansbo’s approximate solutions regarding well resistance and smear is examined in detail by comparing with this rigorous solution. The numerical results reveal that the influence of the disturbance upon the consolidation rate is notably large for the type of soil whose permeability decreases with the disturbance. In this case, existing approximate solutions are shown to be sufficiently accurate for practical application. For the type of soil whose compressibility increases with the disturbance, on the other hand, the influence of disturbance is relatively small. For both soil types, simple equations are proposed to obtain an equivalent “ideal” well having an increased spacing ratio on the basis of analytical results derived from the rigorous solution.