Engineering characteristics of soft soil foundations improved by fine-sand-filled geocell cushions

In the Dhaka Ring Road Project in Bangladesh, geocell filled with fine sand was used as cushions to treat the soft foundation to improve its bearing capacity. Large-scale direct shear, tension, and compression tests were conducted using a self-design testing device to analyse the working characteristics of the fine-sand-filled geocell cushion layer. The FLAC 3D software was used to study the stress and deformation characteristics of a soft soil foundation reinforced by the fine-sand-filled geocell with different embankment heights, numbers of cushion layers, and foundation deformation moduli. The results revealed that the geocell can improve the shear strength of fine sand, particularly in the cohesive force, with increases in the range of 8–21 kPa. Under the reinforcement effect, the fine-sand-filled geocell layers exhibited desirable tensile and compression properties. Installing two fine-sand-filled geocell layers is generally advantageous. Additionally, foundation deformation is highly sensitive to embankment height and foundation strength. The height of an embankment constructed on a soft foundation with a foundation modulus lower than 2.5 MPa should not exceed 6 m. The results of this study may provide a theoretical basis for the application of fine-sand-filled geocell cushion layer in practical engineering.