Numerical Investigation of the Stability of High and Steep Rock Slope Reinforced with Rock Bolts

Excavation-induced unloading alters the stress distribution and support demand in high and steep rock slopes. This study investigates a rock slope near the mainline toll station of the Xiangyang–Yichang Expressway. A FLAC3D model simulates seven-stage excavation. Displacement, plastic-zone distribution, factor of safety, and bolt axial force are presented for unsupported and sequentially supported conditions. Rock-bolt support reduces the final maximum total displacement from 2.895 to 1.442 mm, a reduction of 50.2%. It also increases the factor of safety from 1.129 to 1.316, an increase of 16.6%. The factor of safety reaches a temporary peak at Stage 3 without support and at Stage 4 with support. It then decreases. The maximum bolt force increases sharply at Stage 6. This indicates increased support demand during the later excavation stages. Comparisons with field measurements yield a mean absolute relative error of 11.6% for slope-surface displacement. The monitoring points lie near the heads of the bolts carrying the stage-wise maximum axial forces. The mean absolute relative error of the computed maximum bolt axial force is 9.7%. Five fixed monitoring locations further characterize the spatial distribution and temporal evolution of local responses. Sensitivity analyses examine bolt length, inclination, and horizontal and vertical spacing. They quantify the effects of these parameters on the factor of safety. The results clarify the relationship between excavation sequence, reinforcement mobilization, and slope stability for the investigated slope.