The purpose of the Effective Stress principle in soil is to understand:

The Effective Stress principle in soil mechanics is fundamentally crucial for understanding the behavior of soil under mechanical loads. This principle states that the effective stress, which is the stress that contributes to soil's shear strength and stability, is equal to the total stress minus the pore water pressure.

When soil experiences mechanical loads, the total stress applied must be interpreted in relation to the pore water pressure present in the soil pores. The balance between these stresses determines how the soil will deform, consolidate, and ultimately support structures. Therefore, effective stress directly influences the load-bearing capacity of the soil and is vital for predicting how soils will react under various loading conditions.

While other concepts mentioned, such as pore water pressure, consolidation processes, and moisture content variations, are related to soil behavior, they are more specific aspects that fall under the overarching principle of effective stress. Effective stress encompasses these phenomena, allowing for a comprehensive understanding of the mechanical behavior of soil when subjected to external loads.