Effect of disturbed zone thickness on rock slope stability

Cut slope surfaces are affected by excavation activities and weathering agents. Disturbances on the surface can penetrate down to a certain depth. Slope stability analyses made on the cut slopes can reveal unsatisfactory results unless the disturbance depth is determined. Moreover, false designs ignoring the shear strength parameter differences of inner and surface sections of the slopes can affect the safety of the highways. Disturbance thickness due to blasting effect is already presented in the literature; however, the mechanical excavation is still unknown. In this study the effect of mechanical excavation on disturbance thickness is investigated by using 54 cut slopes selected from Western Black Sea Region of Turkey. According to UCS results, the strength values of the undisturbed zones are found to be two times higher than the disturbed zones. The disturbance depths formed by excavation and weathering are found to be changing between 0.05 and 0.50 m on the cut slopes. Regarding the height (H) of the slopes, disturbance thickness is found to be affecting the slope up to 0.06 H which is lower than the blasting effect. It is recommended that this thickness should be taken into consideration when assigning the disturbance factor (D) and used to prevent stability problems of the cut slopes.