Understand Terzaghi's principle: the total stress at a point in soil is carried partly by water pressure (which can't resist shear) and partly by the soil skeleton (effective stress) — and it's effective stress, not total stress, that controls soil strength and settlement.
Total Stress σ
196.0 kPaPore Pressure u
78.5 kPaEffective Stress σ'
117.5 kPaTotal stress: σ = γ_moist·zw + γ_sat·(z − zw) (for z below the water table)Pore pressure: u = γw·(z − zw)Effective stress: σ' = σ − uMove the point above the water table (depth z less than water table depth zw — for example z = 2, zw = 5). Confirm pore pressure is 0 and effective stress equals total stress.
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