Experimental investigation of rapid penetration of cylindrical rods into granular materials

Penetration into granular media entails a complicated process. A study is presented on the penetration of different cylindrical rods into dry fused quartz and transparent soil at an impact velocity of 5 m/s under measurement of internal flow fields. The influences of the rod nose shape and rod size on penetration are examined. The penetration depth history curves in dry fused quartz and transparent soil (saturated fused quartz) are different due to the hydrodynamic drag effect of the pore fluid. The penetration depth in dry fused quartz is larger than that in transparent soil. In dry fused quartz, the penetration depth of the cylindrical rod is notably related to the total drop height as a power function, which is not observed in transparent soil. The normalized penetration depth d/(Vs P0) is independent of the kinetic energy but depends on the cylindrical rod diameter in transparent soil. This study found that the collision time tc did not depend on the impact velocity (> 1.5 m/s) and geometry of the cylindrical rods. The scaled collision time Tc = tc[ρsR2/(g2ρp)]−1/4 was linearly correlated with the scaled velocity V0(Rg)−1/2 during cylindrical rod penetration. The governing kinetic energy equation was extended to describe the penetration of cylindrical rods with different head shapes and sizes. Visualization with the transparent soil model indicated that the flat-head cylindrical rod could induce more vertical displacement but less lateral movement of soil particles. The cone-head cylindrical rod tended to induce both less horizontal and lateral displacement.