Abstract: Aiming at the consolidation problem of composite ground with granular columns, the calculation model for the consolidation of composite foundation in consideration of vacuum-surcharge preloading and uniform distribution of initial excess pore water pressure is established. The general analytical solution for the consolidation of composite ground under vacuum-surcharge preloading is given, and the variation regularity of excess pore pressure and consolidation degree is discussed. Research findings demonstrate that the excess pore pressure and consolidation degree of composite ground are much more affected by pile diameter ratio (n), disturbance area (s), loading method and time factor (T_h). The greater the values of n and s are, the greater the excess pore pressure is, and the slower the consolidation is; the greater the load is, the greater the excess pore pressure is. Excess pore pressure rises as depth increases, and such increase is more apparent in the shallow part of the foundation, while attenuates in the deep. The effects of vacuum loading and surcharge loading can be superimposed. In addition, the changes of time factor (T_h) have important influence on the distribution law of excess pore water pressure: excess pore pressure distributes linearly in the shallow part of the foundation, but distributes nonlinearly when depth exceeds a certain value, and such nonlinearity gets more evident when the value of T_h is larger.

Key words: composite ground with granular columns, vacuum-surcharge preloading, initial excess pore water pressure, consolidation, analytical solution