In the equation σ' = γ1H1 + H2(γ2 - γw), what does H1 represent?

In the equation σ' = γ1H1 + H2(γ2 - γw), H1 represents the height of soil above the groundwater table. This component is crucial for understanding effective stress in soil mechanics, particularly in saturated and unsaturated soil conditions.

In this equation, γ1 represents the unit weight of the soil above the groundwater table, while H1 is the vertical distance from the surface of the ground down to the groundwater table. The effective stress (σ') is impacted by the weight of the soil above the groundwater and the pore water pressure below it.

Understanding H1 as the height of soil above the groundwater table reflects how this portion of the soil contributes to the overall effective stress experienced by the soil layers below. This concept is essential when evaluating soil behavior for engineering applications such as foundation design and slope stability analysis.

Other potential interpretations of H1, such as the depth below the groundwater table or other aspects in the context of surcharge or excavation, do not accurately capture its significance in relation to effective stress calculations, and thus do not align with the accepted definitions in soil mechanics.