Rainfall-induced landslides are a significant hazard in areas covered by granite residual soil in northern Guangdong Province. To study the response of granite residual soil landslides to rainfall, the most severely affected area during the floods in June 2022 and April 2024 was chosen as the study area. Geological investigations and field artificial rainfall tests were conducted to explore the deformation evolution characteristics of granite residual soil slopes under continuous heavy rainfall and to reveal the failure mechanism of rainfall-induced landsliding events. The results indicate that the granite residual soil can be divided into two layers, and the slope structure can be subdivided into three models from the geological point of view. Given that the deformation and failure characteristics of the surficial landslides are highly similar across the three models, the three models can be consolidated into a single model composed of granite residual soil and weathered granite. The intensity and persistence of rainfall are the main triggering factors of landslides in this area. The landslides are primarily characterized by surficial sliding with a traction sliding failure mode, mainly involving a granite residual soil layer thickness of about 1-3 m. The increased rate of water content and the range of pore water pressure can be used as primary indicators for slope deformation and failure. Additionally, shear dilatancy deformation during slope movement effectively mitigates deformation rates. Furthermore, debris flow is identified as a secondary disaster resulting from landslides, with landslide deposits serving as potential sources for debris flow.

The geometric properties of fracture surfaces significantly influence shear-seepage in rock fractures, introducing complexities to fracture modelling. The present study focuses on the hydro-mechanical behaviours of rough rock fractures during shear-seepage processes to reveal how dilatancy and fracture asperities affect these phenomena. To achieve this, an improved shear-flow model (SFM) is proposed with the incorporation of dilatancy effect and asperities. In particular, shear dilatancy is accounted for in both the elastic and plastic stages, in contrast to some existing models that only consider it in the elastic stage. Depending on the computation approaches for the peak dilatancy angle, three different versions of the SFM are derived based on Mohr-Coulomb, joint roughness coefficient-joint compressive strength (JRC-JCS), and Grasselli's theories. Notably, this is a new attempt that utilizes Grasselli's model in shear- seepage analysis. An advanced parameter optimization method is introduced to accurately determine model parameters, addressing the issue of local optima inherent in some conventional methods. Then, model performance is evaluated against existing experimental results. The findings demonstrate that the SFM effectively reproduces the shear-seepage characteristics of rock fracture across a wide range of stress levels. Further sensitivity analysis reveals how dilatancy and asperity affect hydraulic properties. The relation between hydro-mechanical properties (dilatancy displacement and hydraulic conductivity) and asperity parameters is analysed. Several profound understandings of the shear-seepage process are obtained by exploring the phenomenon under various conditions. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

The study of the constitutive relationship of lunar soil is the key to a deep understanding of the mechanical properties of lunar soil. Previous models mostly focused on the strengthening behavior, while rarely reflected the post -peak softening and residual deformation stages during shear deformation. A new elastoplastic constitutive relation is derived with combining kinematic hardening model and initial shear stress, which effectively compensates for the shortcomings of existing constitutive models, and the validity of the model is verified by comparing with existed laboratory test results. The developed constitutive model not only effectively captures the shear dilatancy and softening characteristics of lunar soil simulant, but also only requires fewer parameters to be easily determined by simple initial loading curves from direct shear tests, Furthermore, the influences of some key parameters on shear strength and softening behavior of lunar soil simulant can be easily obtained based on this constitutive model.