Abstract: Due to the varying properties of different soil layers, the choice and dosage of soil conditioners for EPB shield tunnelling vary accordingly. Adaptability studies of conditioning parameters are needed based on soil properties. For the common gravel layers in shield tunnel projects in Shenyang, a method combining foam agent and bentonite slurry was used for soil improvement. Using a self-made pressurized rotational shear device, parameters such as shear strength, compressibility, and viscosity coefficient of the conditioned soils were measured. The influence of foam concentration, foam injection ratio, bentonite slurry concentration, and bentonite slurry injection ratio on the performance of the conditioned soil was investigated. The experimental results show that the foam agent had a more significant effect on the flow plasticity of the conditioned soil than the bentonite slurry, while the bentonite slurry had a more significant impact on the shear strength. The optimal ratio for soil conditioning in gravel layer was deter? mined.