Centrifuge Test and Numerical Simulation on Failure Mechanism of Channel Slopes with Pre-existing Fractures

In water diversion projects, the stability of deep-cut channel slopes traversing expansive soil strata is a critical geological issue affecting project safety. Pre-existing gentle-dip fissures, occurring in deep layers and inclined towards the channel, are a key geological factor controlling the stability of such slopes. To investigate the progressive failure mechanism and stability patterns of slopes governed by such fissures, a combined
approach of centrifuge model testing and finite element numerical simulation was employed. The pre-existing fissure plane was simulated using a double-layer geome mbrane with an oil film interlayer. The entire process of deformation, crack propagation, and sliding failure of an expansive soil slope containing a bilinear (gentle dip 12° + steep dip 48°) pre-existing fissure under hypergravity loading was studied. The results indicate that: (1) Slope instability exhibits a four-stage characteristic: crest settlement and cracking, horizontal displacement of the slope face, acceleration of deformation, and overall sliding along the gentle-dip fissure plane. (2) The fissure connectivity rate has the most significant impact on stability; when it increases from 67% to 100%, the safety factor decreases by 16.1%. (3) The slope angle also has a considerable influence on stability; as it increases within the range of 40° to 50°, the safety factor decreases by 32.7%. (4) Numerical simulations validated the experimental failure mode and revealed that low-strength fissure planes induce deep-seated bilinear sliding, whereas under high-strength conditions, failure shifts to a shallow circular arc mode. The findings of this study provide a theoretical basis for the stability assessment and disaster prevention and control of fissured expansive soil channel slopes.