Nonlinear analytical solutions for vertical drainage consolidation of foundations under vacuum-surcharge preloading combined with electroosmosis

Based on the equal strain assumption and nonlinear permeation and compression models, analytical solutions for instantaneously loading, single stage loading and multi-stage loading under combined electroosmosis- vacuum-surcharge preloading, considering the variations of vacuum degree with depth and time, the decrease of additional stress with depth, and the decrease of effective voltage with time, were proposed. The proposed analytical solution was validated by comparing with the experimental and numerical results in the literature, and a parametric study was conducted to investigate the variations of the vacuum degree, the additional stress and the effective voltage with depth and time. The results show that the reduction of the vacuum degree with depth will induce the decrease of the maximum negative pore water pressure and the settlement but has little influence on the consolidation rate. The initial consolidation rate increases nonlinearly with the increase rate of the vacuum degree. The multi-stage loading will effectively decrease the excess pore water pressure induced by loading, which ensures the stability of the soft foundation after loading. The excess pore water pressure and the final settlement will decrease obviously due to the reduction of the additional stress along depth. The larger the residual value of the effective voltage or the smaller the decrease rate of the effective voltage, the larger the maximum average negative pore water pressure and the settlement. Moreover, the consolidation rate decreases nonlinearly with the decrease rate of the effective voltage. © 2021, Science Press. All right reserved.