Abstract: To investigate the stress characteristics of existing bolts and slope stability during secondary excavation in a slope reconstruction and expansion project, we conducted centrifugal test by using self-developed bolt angle support device for model test.The horizontal displacement at the slope’s crest, bolt axial force, and soil pressure throughout the excavation process on a bedding rock slope were examined. The anchoring angles studied were 10°, 20°, 30°, 45°, and 60°, with one bolt per 18 cm and per 12 cm, respectively. Results indicate that under the same anchoring angle, cumulative horizontal displacement at the crest increases nonlinearly with slope unloading, notably exceeding that at the mid-slope. The axial force of bolt exhibits a unimodal distribution, peaking during excavations at slope crest and toe. Peak axial force, near the weak surface, initially declines and then rises with excavation unloading, remaining over 61% of pre-excavation levels. As anchoring angle increases, slope crest displacement initially decreases then rises, while soil pressure follows an inverse trend, suggesting an optimal anchoring angle. We recommend staged slope excavation, with reduced excavation rates at the crest and toe. Slope gradient, rock strata, and weak surface inclination should be considered in anchoring angle design for optimal performance.The research findings are conducive to selecting appropriate support measures in secondary excavation of slopes.

Key words: high slope, existing bolt, secondary excavation, centrifugal test, bolt angle, bolt density