Study On The Consolidation Theory Of Composite Ground With Granular Columns

Although great progresses had been made on the consolidation theories of composite ground with granular columns, there were still some shortcoming in these theories because they cannot consider the many influencing factors existed in practical engineering, such as impeded boundaries, non-uniform distribution of initial excess pore water pressure and permeability change in surrounding soil caused by disturbance during the process of the installation of granular columns. In this dissertation, the consolidation theory of composite ground with granular columns was studied in-depth and systematically by analytical method, and the analytical solutions closer to actual cases were obtained to enriched the consolidation theory and to provide new technical supports to soft ground improvement. The original work was as follows:1. The consolidation problem of soft soil improved by granular columns with double impeded boundaries was studied, and the corresponding analytical solution obtained. The solutions so far available for consolidation of composite ground with granular columns under equal strain condition were all the special case of the developed solution. It shows that the permeability of impeded layers affects the consolidation of the composite ground, and the greater the permeability are, the faster the consolidation is. However, such influence is not significant comparing with other factors.2. Based on "the method of double-layered soil" proposed by Chen (1984), a simply solution to the consolidation of composite ground with partially penetrated granular columns was obtained, and the one to the consolidation of soft soil improved with partially penetrated vertical drains was also given as a special case of this simply solution. It shows that the solution has sufficient accuracy in view of practical use.3. The consolidation of the composite ground under non-uniformly distributed initial excess pore water pressure along depth was studied in two models which respectively considering both the radial and vertical flows in granular column and the vertical flow only in granular column, and the corresponding analytical solutions of the two models were presented and compared with each other. It shows that the distribution of initial excess pore water pressure has obvious influence on the consolidation of the composite ground with single drainage boundary, and the rate of consolidation considering the radial-vertical flow in...