Liren Ban

The anisotropy parameter of joint surfaces reflects the mechanical and physical properties of joint surfaces in different directions, which significantly affects their stability, permeability and the design reliability of rock engineering applications. To quantitatively characterize the anisotropic properties of joint surfaces, a novel method is proposed. This method integrates the morphological distribution characteristics of the actual contact joint surfaces with fractal theory. First, the 3D morphological features of the joint surfaces at various sampling intervals were acquired using 3D laser scanning. The results reveal that the surface morphology exhibits significant anisotropic characteristics and a pronounced sampling interval effect (SIE). Subsequently, the anisotropy of the 3D roughness parameter proposed by Ban et al. is investigated. To investigate the SIE on the accuracy of roughness characterization, a new 3D fractal roughness parameter is developed by incorporating fractal theory. Finally, a method is proposed to quantify the anisotropy based on the fractal features of the actual contact joint surface according to the variation of the fractal parameter in different directions. Furthermore, the size effect on fractal parameters in different shear directions is further investigated. The results demonstrate that the impact of the size effect on fractal parameters depends on the shear direction, and the parameters tend to stabilize with increasing observation scale. The anisotropy parameter proposed in this study is influenced by both normal stress and joint material properties, and it reflects the anisotropy of the actual contact 3D roughness under specific loading and material conditions.

In earthquake engineering and hydraulic engineering, the dynamic mechanical behavior of cohesive soils is crucial to ensure structural stability. However, most existing dynamic constitutive models fail to adequately account for the influence of strain history, which is essential for accurately predicting soil behavior under seismic loading. This study conducted a series of cyclic single-shear tests on both in situ and disturbed Changsha cohesive soils. Hysteresis curves were obtained under varying shear strain amplitudes to investigate the degradation patterns of the dynamic shear modulus and the evolution of the damping ratio. Furthermore, multi-cycle loading tests under constant strain amplitude were carried out to clarify the correlation between damping ratio, dynamic shear modulus, and the number of loading cycles. A simplified practical dynamic model, applicable to general cohesive soils, is proposed. This model incorporates the effect of strain history and provides a valuable reference for analyzing the dynamic response of soils subjected to earthquake actions.