Numerical characterization of tapering features in non-uniform weak interlayers for proposed slope stability geometry

Abstract

Folding and subsequent pinching out are common geological features in geologically active areas. This gives layers a non-uniform thickness, especially for a multilayer slope with a weak interlayer. Thickness non-uniformity is often disregarded in stability analysis to simplify slope models. However, the geometrical variability of rock masses always exists, and the impact is inevitable; therefore, it is not to be discounted. This research systematically established a geometric correlation framework to understand how tapering configurations in weak interlayer influence slope stability in layered rock masses. Analytical and numerical methods are implemented using the RocScience code. Statistical analysis was also performed to assess the significance and correlation of tapering configurations to slope stability conditions. It was found out that Tilting Intensity (ρ≥0.736) and Thickness Gradient (ρ≥0.743) consistently exhibited the strongest (α=0) negative correlation with critical strength reduction factors and slip surface radius, confirming that taper steepness and vertical irregularity are the dominant geometrical destabilizers in non-uniform weak layers. Moreover, stratigraphic unevenness not only exerts a direct destabilizing influence but also modulates the sensitivity of other geometrical parameters, such as the aspect ratio, by a factor of 2 units ΔFS recorded at the highest elevation. The findings of this study carry several practical and scientific implications for slope design, geomechanical modeling, and geological interpretation in complex stratified rock masses.