Abstract: To analyze the optimal position of horizontal drainage sand blanket in reclaimed foundation, the case that a double-layer foundation with placement of a single sand blanket is considered, using the method of separation of variables, and the analytical solution of excess pore-water pressure and average degree of consolidation is obtained. Their validity is verified by degeneration and finite element method. The effects of the lower foundation permeability coefficient to the upper foundation permeability coefficient ratio (a), the lower foundation volumetric compression coefficient to the upper foundation volumetric compression coefficient ratio (b) and the lower foundation thickness to upper foundation thickness ratio (c) on the optimal position of the sand blanket are discussed. Finally, an example is given to demonstrate different consolidation efficiencies of the foundation when the sand blanket is placed at different positions. The results show that at the same time factor, when 1, the optimal position of the sand blanket moves downward with the increase of a, but when 1, the opposite becomes the case. The optimal position of the sand blanket moves downward with the increase of b when 1, and when 1, the opposite becomes the case. When the consolidation coefficient of the lower foundation is greater than that of the upper foundation, the optimal position of the sand blanket moves upward with the increase of c in the early stage of consolidation, and the opposite becomes the case in the later stage of consolidation. The calculation results show that when the average degree of consolidation of foundation reaches 90%, the sand blanket is placed at the optimal position, which saves a lot of time compared with the unpaved sand blanket.

Key words: double-layer foundation, horizontal drainage sand blanket, permeability coefficient, optimal position of sand blanket