Semi-analytical solution for one-dimensional consolidation of a two-layered unsaturated-saturated soil system ground with a horizontal drainage layer

The horizontal drainage layer is widely used in blow-filling and road foundation-filling projects. Due to the change in the groundwater table and horizontal drainage layer, the double-layer ground sometimes shows two states of unsaturated and saturated. Meanwhile, the two-layered unsaturated–saturated soil system ground is very widely distributed in nature. In this paper, based on the soil consolidation theory, semi-analytical solutions of excess pore pressures and the settlement of a two-layered unsaturated–saturated soil system containing a horizontal drainage layer under different drainage layer boundary are obtained by using the Laplace transform technique and decoupling method. And the model in this paper can be well degraded to two classic soil consolidation ones and presents an excellent agreement with references, showing excellent accuracy and reliability of the solutions obtained in this paper. Further, by selecting parameters to analyze their effects on the consolidation of the modelling in this paper. The results show that the horizontal drainage layer can provide additional drainage channels to accelerate the consolidation of two-layered ground in an unsaturated–saturated soil system, while the location of the horizontal drainage layer at 0.3H-0.5H can most efficiently accelerate the ground consolidation process. When drainage conditions are poor, the settlement completion time is prolonged.