The influence of scale effect on the deformation parameters of the Duncan-Chang E-μ model for coarse-grained soils: an experimental study

The influence of scale effect on the deformation parameters of the Duncan–Chang E–μ model (hereinafter abbreviated as D–C E–μ M) for coarse-grained soils remains challenging to quantify. These parameters play a critical role in predicting deformations in earth-rock dams, which in turn directly affect the safety and durability of such structures. Therefore, mitigating the impact of the scale effect on the deformation parameters of the D–C E–μ M is essential for the safe design of earth-rock dam projects. Previous studies suggest that variations in the maximum particle diameter d max and the gradation structure are the primary factors contributing to the scale effect. In this study, the influence of scale effect on the mechanical behavior of coarse-grained soils is systematically investigated. Using a continuous gradation equation, 21 sets of specimens with different gradations were prepared by controlling d max and the gradation area S. A series of triaxial consolidated-drained tests were conducted to analyze the effects of d max and S on the deformation parameters of the D–C E–μ M. The experimental results indicate that parameters G , K , F , and Rf decrease as the gradation area S increases. In contrast, parameters n and D first increase and then decrease with increasing S , eventually stabilizing beyond a certain threshold. Empirical relationships between each model parameter and S were established. With increasing d max , the parameters R f , lgK , n , F , and D increase, whereas G decreases. All parameters exhibit logarithmic relationships with d max . Based on the similar gradation method, an empirical formula is proposed to predict the deformation parameters of the D–C E–μ M under the influence of scale effect. The applicability of this formula to various types of coarse-grained soils is validated using test data from existing literature. Finally, a method is presented for predicting in situ deformation parameters of the D–C E–μ M based on scaled laboratory test results using the similar gradation approach.