Experimental study of different typical shape falling-rocks impacting on the sand cushion and dimensionless analysis

An experimental study on the impact force and penetration of falling rocks with three typical shapes, including spherical, conical and flat shapes, against the cushion was carried out. The experimental results show that the shape of the falling rock has a significant influence on the impact results. Under the same conditions, the flat blocks have the highest impact force, the lowest penetration depth and the shortest peak impact time, and the opposite for the conical falling rocks, with spherical blocks are between the two. The dimensionless analysis method was adopted to convert the mass, velocity, shape, size of the falling rock, the strength and density of the cushion layer into the dimensionless strength impact factor I, density impact factor λ and shape impact factor ψ. The correlation analysis between the impact factors and penetration test data shows that: (1) The effects of the impact factors I and λ on the final depth of penetration zm/d are similar. (2) The analysis of the impact factors I and λ effects on penetration depth shows that I and λ are relatively independent. The pattern of the I effects on the depth of penetration is generally consistent for different λ values.