A Technique for the Measurement of the Morphological Evolution of Marine Pebbles

The scope of this paper is to present an innovative methodology for the measurement of the volume evolution of marine pebbles, subject to action of wave motion. This technique is based on the 3D scanning of the pebbles at different stages of the abrasion process, and on the actual measurement of the volume, as well as other ancillary parameters (e.g., the mass) through the use of 3D graphic tools. The 3D scanning of the pebbles is performed using a commercial, low-cost 3D scanner and a mechanical structure which allows the acquisition of the complete pebble morphology. In order to validate the technique, two laboratory tests were performed. In a preliminary test, the 3D model of four pebbles of specific shapes was acquired for a total of 50 times, in order to evaluate the repeatability of the 3D acquisition and then of the volume measurement. The second set of tests was performed using a Los Angeles (LA) tumbling machine, to simulate the natural abrasive process. Then, the 3D models of a number of pebbles were acquired at different stages of the LA machine operative procedure. The results demonstrate the effectiveness of the proposed technique and motivate their usage in a natural environment, that is being carried out in Marina di Pisa, Italy.