Creep behavior of slip zone considering the rivalry between soil hardening and damage: case study of a giant colluvial landslide

Large colluvial landslides often exhibit creep characteristics influenced by slip zones, whose behavior is closely related to their inherent structure and stress conditions. To investigate this, a triaxial compression creep test on undisturbed slip zone soil was conducted. The results revealed that the soil exhibited a short period of attenuation creep following temporary deformation, then quickly transitioned into the steady creep stage. A rivalry mechanism between hardening and damage effects was suggested to explain and quantitatively characterize the various stages of creep. On this purpose, a three-dimensional constitutive model (H-D3D) was constructed to effectively capture the staged creep behavior, demonstrating higher accuracy over the Burgers-Mohr model in replicating structural soil responses. A sophisticated approach to solving model parameters was also put forth, considering well the characteristics of each creep stage. After that, the H-D3D model was implemented in FLAC3D through secondary development to numerically solve the complex creep behavior of slip zones and landslides. The results demonstrate that employment of the suggested model successful represents the staged deforming behavior of the targeted landslide that is influenced by fluctuating water levels, confirming the accuracy as well as applicability of the proposed model. Therefore, this research introduces a critical theoretical framework and computational tool for analyzing the deformation behavior of colluvial landslides.