A Statistical Damage Constitutive Model for Graded Gravels Incorporating the Degree of Compaction and the Damage-Softening Index

Strength characteristics of graded gravels are essential in the construction of roadway and railway substructures. Traditional constitutive models, primarily nonlinear elastic and plastic types, fall short in accurately capturing the strain-softening properties of such materials. To address this limitation, the current study introduces a statistical damage model designed to outline the stress-strain behavior of densely compacted graded gravels in transport infrastructures. Utilizing medium-sized triaxial tests, the model examines variations in strength and deformation parameters in relation to compaction levels and incorporates a unique damage-softening index (DSI) along with a threshold axial strain to improve accuracy. The study establishes that the DSI and threshold axial strain effectively regulate stress-strain relations in the postpeak segment, the model's statistical parameters and threshold axial strain can be precisely determined through the introduction of DSI, and the model closely aligns with experimental data across multiple compaction levels. These findings are especially relevant for engineering design in the context of roadway and railway construction and indicate potential for further refinement, such as the incorporation of loading rate considerations.