Physical model test study on unlocking mechanism for slopes containing a locked segment with anti-dip weak planes

Failure and instability of locked-segment-type slopes are characterized by rapid initiation, sudden onset, and severe damage. Predicting such failures has become a major focus in engineering geology, and research on the unlocking mechanisms of locked-segment-type slopes that account for the internal structural characteristics of locked segments is urgently needed. In this study, the Chana landslide, a typical slope containing locked segments with anti-dip weak planes, was adopted as the geological prototype. A geomechanical model of a locked-segment-type slope with anti-dip weak plane was developed, and a physical model study was conducted to investigate its unlocking mechanisms. Slope models with anti-dip weak planes inclined at 5° and 10° were constructed and subjected to slow incremental loading to reproduce the processes of slope deformation and failure. The resulting slope failure patterns were analyzed to clarify the influence of the inclination of the anti-dip weak plane on slope instability. A method for determining the locked-segment range was proposed based on the strain concentration zones observed in the physical model tests, which allows calculation of the damage evolution of a locked segment during slope instability. On the basis of the mechanical relationship between the points of volume expansion and peak strength of the locked segment, the instability evolution process of the slopes was retrospectively predicted, yielding satisfactory results. These findings provide important theoretical insights and practical applications for predicting instability and preventing disasters in locked-segment-type slopes.