Final answer:
Increasing effective stress leads to an increase in volumetric strain due to the bulk stress affecting volume change. In terms of gaseous equilibria, Le Chatelier's Principle describes how shifts occur in response to pressure changes, favoring the side of the reaction with fewer moles of gas when pressure increases.
Step-by-step explanation:
When we increase the effective stress, the result is an increase in volumetric strain in a material. This change is a manifestation of bulk strain, which is caused by bulk stress, indicating a change in volume relative to the original volume. Le Chatelier's Principle explains how a system at equilibrium responds to a stress, such as increased pressure, by shifting to mitigate the stress. In the context of gaseous equilibria, increasing pressure by decreasing volume will cause the system to shift towards the side with fewer moles of gas. Conversely, decreasing the pressure would shift the equilibrium towards the side with more moles. When interpreting the effects of effective stress on a material's volume, especially in engineering, we account for the changes in volumetric strain that occur as a result of this increased stress.