Deformation and failure evolution mechanism of valley slope induced by dominant crack propagation: Insights from transparent soil modelling

Rock slope failures occur frequently in mountainous regions. However, research on the internal deformation and failure evolution mechanism of fractured valley rock slopes caused by dominant crack propagation remains limited. To address this knowledge gap, this study used the bank slope of the newly constructed Nujiang Grand Bridge as a prototype to perform model tests on slopes with dominant cracks at the slope top (M₁ model) and slope toe (M₂ model) utilizing a self-developed visualized model experiment system. Experimental data from the top load and displacement cells, along with the Particle Image Velocimetry (PIV) technique, were utilized to analyze the load-displacement response curves, displacement, velocity, strain rate fields, and propagation characteristics of the dominant crack in the slope. The results indicated that: (1) the load-displacement curves for both M₁ and M₂ models could be divided into four stages: slow acceleration, approximately uniform increase, slow deceleration, and rapid decline. The ultimate bearing capacity of the M₂ model was about 3.2 kN larger than that of the M₁ model. (2) The deformation and failure process of the slopes in both models could be categorized into three stages: initial deformation, rapid deformation, and failure. The M₁ and M₂ models exhibited “thrust-type” and “retrogressive” landslide failure characteristics, respectively. (3) The length of the dominant crack propagation segment increased exponentially with increasing loading duration, and the slope deformation showed obvious zonal characteristics. (4) The comparison of deformation and failure characteristics between the model and prototype slopes validated the rationality and accuracy of the model test. This study offers valuable insights into the internal deformation and failure evolution mechanism of fractured valley slopes resulting from dominant crack propagation.