Impact of Rock Debris on a Simply Supported Beam.

Sedimentary and igneous rock projectiles were fired at the center of a simply supported aluminum beam in a series of impact tests. An experimental investigation was conducted to determine: dynamic response of the beam, localized permanent deformation of the beam in the region of impact, and fracturing behavior of weak and strong sandstone. The experimental results are complemented with the development of analytical impact models for both fracturing and nonfracturing rock projectiles. An impact apparatus was developed for firing regular and irregular shaped projectiles. Response of strain gages attached to the 0.25 x 1.00 x 18.00 in., 6061T6 aluminum beam, were recorded on a storage oscilloscope and oscillograph recorder. 16-mm high speed films of the impact process, were taken at just under 6000 frames/s. These films provided projectile and beam displacement data both during and after impact and also the means of determining the time duration of impact in the case of single impact, in addition to time between impacts in the case of multiple impact.