Abstract：For conventional reinforced soils，the reinforcements are often laid horizontally in the soil. A novel concept of three-dimensional reinforced soil is proposed in this paper. In the proposed 3D reinforced soil，besides the conventional horizontal reinforcements，some vertical and three-dimensional reinforcing elements are also placed in the soil. A series of triaxial tests are carried out on reinforced sand with two-layer horizontal-vertical 3D reinforcements and vertical reinforcements respectively. The results of triaxial tests show that the ultimate deviator stress at failure increases greatly for three-dimensional reinforced sand compared with unreinforced sand and horizontally reinforced sand. Furthermore，the internal friction angle of three-dimensional reinforced sand increases significantly；and cohesion exhibits a similar tendency. The behaviors of sands reinforced with different three-dimensional reinforcing configurations and different reinforcing ratios are studied in terms of stress-strain relationship and shear strength of sand. Based on the experimental results，the mechanism of the three-dimensional reinforced soil has been analyzed and the strength model of the two-layer three-dimensional reinforced sand has been proposed by means of the limit equilibrium theory. The results of analytical prediction are compared with those obtained from the triaxial tests. It is shown that the results of the analytical solution are in good agreement with those from triaxial tests.
