Grain size dependence of yield stress in marble

The data collected indicate that the yield stress of marble increases linearly with the inverse square root of the mean grain size. Increased confining pressure to 2 kbars causes the grain size effect to become more pronounced, whereas increased temperature to 300°C causes this effect to become less important. The Petch [1953] theory of the yield stress-grain size relationship, although it is in partial agreement with the data, is found to be incomplete.