Baseball and softball are played primarily on the infield skin. An ideal infield surface allows players` cleats to penetrate the soil and provide adequate traction yet impart minimal surface disruption. This ideal state has been termed the "cleat-in/cleat-out effect." As an infield soil dries, it transitions from the cleat-in/cleat-out state to a brittle condition in which the soil readily fractures into chips or clods. . Surface irregularities formed in the brittle condition may deflect batted balls and induce a fielding error or injury. The objective of this research was to develop a laboratory test for identifying the critical water content corresponding to the cleat-in/cleat-out behavioral threshold for any soil. A pneumatically driven apparatus was fabricated to emulate an athlete`s footstrike by applying normal, shearing, and torsional stresses using baseball cleats removed from a commercially available shoe. The test produced several cleat indentations on a cylindrical soil sample. A 3D scanning technique quantified surface disruption via Dirichlet Normal Energy. Volumetric water content was measured using a combination of 3D scanning and gravimetric methods. A given soil sample was tested at several water contents. was determined by plotting Dirichlet Normal Energy against and fitting a curve to solve for the local minimum. The method successfully detected differences in between infield soils containing identical clay mineralogy but differing sand content (60% and 75%; p < 0.001). Reasonable correspondence was achieved across test replicates, with a coefficient of variation of 8.5%. It is envisaged that the method will find utility in future investigations of infield mix design.
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