An experimental study of the dynamic characteristics of the undisturbed laterite under graded cyclic loading

In order to study the dynamic characteristics of the undisturbed lateritic soil subgrade under cyclic loading, the dynamic triaxial tests of undisturbed laterite are carried out with the SDT-20 dynamic triaxial apparatus. The effects of confining pressure, frequency and dynamic stress amplitude on dynamic stress, elastic modulus-strain（E_d-ε_d ） and shear modulus-shear strain（G_d-γ_d） on dynamic behavior are studied. The results show that the development law of the dynamic stress-strain curve of the undisturbed laterite can be described by the Kondner model. The dynamic stress increases rapidly with the dynamic strain and then tends to be stable, and the range of the dynamic strain value is given, that is, 0～0.05%. The elastic modulus-strain and shear modulus-shear strain on dynamic behavior of laterite under different confining pressure and vibration frequency are analyzed. When the dynamic strain is less than the critical value, the dynamic elastic modulus of laterite increases with the increase of dynamic strain. When the dynamic strain is greater than the critical value, the dynamic elastic modulus of laterite decreases with the increase of dynamic strain, and the dynamic shear modulus has the same change rule. Combined with the dynamic characteristics of the laterite material, the dynamic elastic modulus is reduced by the confining pressure, which is established on the basis of the Darendeli model. The segmented prediction model of the dynamic elastic modulus and dynamic shear modulus of laterite subgrade material is proposed in the paper. The applicability of the segmented model is verified by the fitting method, which can predict the development trend of E_d-ε_d and G_d-γ_d curves of laterite under the graded cyclic loading.