Insight into the crack characteristics and mechanisms of retrogressive slope failures: A large-scale model test

Cracks in the crown area are one of the important indicators in the instability of the landslide headscarp, potentially offering early warnings for landslide hazards. Due to the complex causes of crack formation and numerous influencing factors, the understanding of crack development characteristics is still insufficient. In this paper, a large-scale soil slope model test is carried out through a large tilting platform to simulate the whole process of retrogressive slope failures including the first-time failure and the enlargement of the failure. The characteristics of crack development, the relations between internal slope parameters (e.g., internal strain and earth pressure) and cracks, and the evolutionary mechanisms of retrogressive failures are focused. The model test is monitored by high-tech equipment, including optical fibres, pressure gauges, and cameras. The results show that crack developments are divided into four stages based on crack location, quantity, and size. Optical fibre monitoring shows that the areas of tension crack development fall within the negative strain area in the slope model. In addition, the failure mode of the retrogressive landslides can be summarized in three stages: a deformation stage with sparse local cracks, a destabilizing stage with main cracks, and a retrogressive failure stage with dense secondary cracks. This study offers preliminary insights into the relations between crack development and the mechanisms in soil multiple retrogressive failures, which can be beneficial for better identifying and interpreting landslides at sites through crack monitoring.