Abstract: To investigate the mechanical strength and volumetric deformation characteristics of reinforced construction waste fill materials, consolidated-drained triaxial shear tests were conducted on construction waste fill reinforced with three types of geosynthetics using the GDS electromechanical triaxial testing system. Based on the experimental results, the applicability of the Duncan-Chang model was analyzed, and a modified Duncan-Chang model was proposed. The study revealed that both unreinforced and reinforced construction waste fill exhibited strain-softening behavior in their stress-strain curves under varying confining pressures. As the confining pressure increased, the reinforcement effectiveness coefficients of all three geosynthetics gradually decreased. However, the cohesion of reinforced construction waste fill significantly improved, while the internal friction angle showed a maximum reduction of approximately 4.14° compared to unreinforced samples. Reinforcement effectively suppressed soil dilatancy and enhanced volumetric stability. Among the three geosynthetics, fiberglass composite geotextile demonstrated the most pronounced reinforcement effect. The tangent elastic modulus (E) of the Duncan-Chang model was found suitable for describing the stress-strain behavior of reinforced construction waste fill but failed to accurately capture its volumetric deformation characteristics. To address this limitation, a modified Duncan-Chang model was developed by establishing a quadratic function relationship between axial strain (ε₁) and lateral strain (ε₃) and deriving a functional equation linking volumetric strain to axial strain. This modified model effectively characterizes the stress-deformation behavior of reinforced construction waste fill. The findings provide valuable references for the engineering applications of reinforced construction waste fill.