Combined Computational and Experimental Studies on the Bending Cracking Behavior of Red Clay

This study investigates the factors affecting crack development in red clay roadbeds and slopes through a combined computational and experimental approach. A finite-element model of a prefabricated cracked red clay fracture was established using a cohesive zone model, integrating fracture mechanics theory with numerical analysis. The model was based on an improved three-point bending test system to obtain raw data. The effects of prefabricated crack depth, width, shape, and support span on crack propagation in red clay were systematically investigated. The results indicate that the reliability of the model is confirmed by the three-point bending test. The degree of curvature of the crack depth on the Mode I fracture extension was more significant compared with Mixed mode I–II fractures. Variations in prefabricated cracks fracture had minimal impact on peak load and the degree of curvature of the crack extension in Mode I. The maximum crack width and length occurred at a prefabricated crack width of 2 mm, with the lowest curvature observed. Conversely, a crack width of 6.5 mm led to the highest curvature in Mixed mode I–II fractures. The alteration of the prefabricated crack shapes revealed that, for Mode I fracture, triangular prefabricated cracks resulted in the maximum crack width and length, and the lowest degree of crack curvature. The shape of the prefabricated crack had a minor effect on peak load, with triangular tips yielding the longest crack extension length and highest degree of curvature in Mixed mode I–II fractures. Support span had a limited effect on the crack extension path of Mode I fracture; increasing the span led to a 60.4% reduction in maximum crack width and a 28.9% reduction in maximum crack length. In Mixed mode I–II fractures, the support span inversely correlated with maximum crack width and length.