Back-crack locations of water softening-caused retrogressive bedrock–overburden landslides: a case study of Wuhuamiao landslide

This study aimed to investigate back-crack locations of water softening-caused retrogressive bedrock–overburden landslides. First, six laboratory model tests of the Wuhuamiao landslide were performed to investigate the back-crack locations. Then, an analytical model was developed and used to calculate the laboratory back-crack locations. The practical effectiveness of the analytical model was finally evaluated using real Wuhuamiao and Jiangdingya landslides. The test results showed that all six model tests successfully reproduced the retrogressive bedrock–overburden landslides having two sliding masses, a front sliding mass and a rear sliding mass. Each sliding mass had a back crack. The back-crack inclinations varied widely from 59.7° to 77.2° for the six front sliding masses, while the back-crack inclinations varied widely from 59.2° to 69.6° for the six rear sliding masses. The wide variation is mainly due to the difference in the spatial location of sliding mass and the basic shear surface (BSS) location. For the fourteen back-crack surfaces of laboratory and real landslides, the calculated locations were broadly consistent with the measured or published locations.