Laboratory model test and numerical analysis of the unlocked and instability mechanism of locked-segment-type slopes

The failure and instability of locked-segment-type slopes are characterized by their rapid onset，unpredictability，and significant consequences. It is of great practical significance and an urgent social requirement to reveal the unlocked mechanism of such slopes. This study utilizes the Chana landslide as a geological prototype of a typical locked-segment-type slope. A physical model of locked-segment-type slopes is constructed using analogous materials，and the failure and instability processes of the physical model are conducted under gradual step-loading conditions. Furthermore，a numerical model of locked-segment-type slopes is established using the FLAC^3D software platform，and its failure and instability processes are simulated through the strength reduction method. Based on the results from both physical and numerical simulations，the failure and instability modes of the locked-segment-type slope are analyzed，and its unlocked mechanism is finally revealed. According to the concept of the locked segment，an identification method for the locked zone is proposed，based on the strain concentration area observed in the physical simulation tests. Additionally，the damage evolution of the locked segment is analyzed. Utilizing the Fish programming language integrated within FLAC^3D，an acoustic emission(AE) acquisition program is developed to monitor the locked segment area，and the AE evolution characteristics during slope instability are analyzed. Based on the simulation results，an effective identification method for characteristic stress during locked segment damage is proposed，and the evolution stages of slope instability are then divided. Subsequenly，the critical displacement criterion for the instability of the locked segment is employed to retroactively predict the instability process of the Chana landslide，achieving favorable predictive outcomes. The findings enhance our understanding of the instability mechanisms and improve the instability prediction capabilities for locked-segment-type slopes.