Analytical solution for consolidation of vertical drains by vacuum-surcharge preloading

A general analytical solution is obtained for the consolidation of vertical sand foundation under vacuum preloading considering simultaneously the variation of vacuum degree, the coupled variation of stress increment with depth and time, the horizontal and vertical drainage and the variation of horizontal permeability coefficient of soil. Furthermore, detailed solutions are obtained for the excess pore water pressure and average degree of consolidation under the particular situation that the vacuum degree linearly changes along the vertical drain depth, the stress increment linearly changes along the column depth and the loading is applied in a single-stage way. Finally, the consolidation behavior of the vertical drain foundation is analyzed. The results show that if the loading is applied linearly, consolidation degrees of foundation have something to do with the vacuum degree, the larger the vacuum is, the faster the consolidation is, the slower the reducing of vacuum is, the faster the consolidation. If the loading is applied instantaneously, consolidation degrees of foundation have nothing to do with the vacuum degree. Ignoring the vertical flow within the soil will under-estimate the consolidation rate. Furthermore, the less the radius ratio is and the less the ratio of horizontal permeability to vertical permeability is, the greater the under-estimated value is.