Stability and safety criterion of a slope with weak interlayer under blasting vibration

A numerical model of bedding bench slope was established by using the FLAC^3D software. First, the dynamic response law of the slope under the blasting waves was analyzed. Then the stability of the slope was analyzed based on the displacement and the shear strain increment. Finally, according to the judgment of the slope stability, the appropriate velocity safety threshold of blasting vibration was developed. Studies reveal that the attenuation rate of the vibration amplitude decreases with higher blaster center distance value. There is elevation amplification effect on the slope and the main vibration velocity reaches the maximum at the foot of the free surface due to the existence of the weak interlayer. The deformation and failure of the slope is controlled by the weak interlayer. The upper rock mass becomes the potential sliding mass when there is tensile and shear failure in the weak interlayer, and the fracture surface can be determined according to the horizontal displacement map and the plastic zone distribution map. The slope failure is a progressive accumulation, displacement and shear strain accumulation will lead to the mechanical parameters of the rock weakening. There is a permanent displacement after blasting vibration if the slope has a great safety margin, while the slope near the state of limit equilibrium will be instability. The safety threshold of the slope is 21 cm/s if the strata inclination is from 15° to 23°. When the cut out height of the slope with the weak interlayer is 14 m and the strata inclinations are 24°, 29°, 31° and 34°, the corresponding safety threshold will be 10, 8, 6 and 5 cm/s.