Analytical Solution for Consolidation of Combined Composite Foundation Considering the Well Resistance of Stone Columns Varying With Time and Depth Under Bidirectional Seepage

ABSTRACT An axisymmetric bidirectional seepage consolidation model is established for the composite foundation reinforced by stone columns and cement mixing piles. The model assumes that the well resistance of the central and peripheral stone columns increases exponentially with time and linearly with depth. Governing equations and analytical solutions for consolidation under instantaneous and multistage instantaneous loading of uniform external loading are derived by considering the influences of the smear effect of stone columns, the disturbance effect of cement mixing piles, and the coupled radial‐vertical seepage within the soil. The rationality of the analytical solution is verified by degradation analysis. Finally, the present solution under instantaneous loading is adopted to study the influence of several parameters on the consolidation behavior. The results show that considering the clogging effect of stone columns will reduce the rate of composite foundation consolidation, the depth influence factor has minimal effect, and the time influence factor has a greater effect on the late‐stage consolidation. Ignoring the clogging effect, a higher initial permeability coefficient or a denser distribution of stone columns and cement mixing piles leads to faster consolidation. Good agreement can be observed between the settlement predicted by the theoretical solution and measured settlement.