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    Geotechnical / Settlement

    Consolidation Settlement Calculator

    One-dimensional consolidation settlement by layer summation: the compression index, the initial void ratio, the effective stress and the stress increase. The time to 50 % and 90 % consolidation comes from the coefficient of consolidation and the drainage path.

    Primary settlement166.8 mmVertical strain2.78%Time to 50 %0.89 yr
    Primary settlement
    166.8 mm
    For Δσ 50 kPa
    Vertical strain
    2.78%
    Of the layer thickness
    Time to 50 %
    0.89 yr
    Double drainage
    Time to 90 %
    3.82 yr
    Usually the serviceability horizon
    Settlement against stress increase
    Logarithmic, so each doubling of the load adds a constant increment.
    Settlement against stress increase
    ΔσSettlement (mm)Strain (%)
    25 kPa91.81.53
    50 kPa166.82.78
    100 kPa285.24.75
    200 kPa452.07.53
    400 kPa662.211.04

    Secondary compression and creep are not included.

    Inspect the model
    Choose a quick result view, a scaled comparison, or the complete diagnostic set.
    Settlement against stress increase
    The curve is logarithmic in Δσ, not linear.
    Settlement against stress increase0.000148.33296.67445.00593.33741.6625255050100100200200400400mm
    Canonical equations
    The exact relationships implemented by this engine.

    s = Cc·H/(1+e₀)·log₁₀((σ′₀+Δσ)/σ′₀) · Terzaghi 1D consolidation.

    Hdr = H/2 (double) or H (single) · Double drainage is four times faster.

    t = T·Hdr²/cv · T50 = 0.197, T90 = 0.848.

    engineering methodology

    A clear path from inputs to results.

    One-dimensional consolidation settlement by layer summation: the compression index, the initial void ratio, the effective stress and the stress increase. The time to 50 % and 90 % consolidation comes from the coefficient of consolidation and the drainage path.

    Step-by-step methodWorked exampleAssumptions explained

    How to use

    1. Set layer thickness h (m).
    2. Set initial void ratio e₀.
    3. Set compression index cc.
    4. Set initial effective stress σ′₀ (kpa).
    5. Read the headline metrics, then check the table for the detail.

    The formula

    s=CcH1+e0log⁡10 ⁣(σ0′+Δσσ0′)s = \frac{C_c H}{1+e_0}\log_{10}\!\left(\frac{\sigma'_0+\Delta\sigma}{\sigma'_0}\right)

    Reference: Terzaghi one-dimensional consolidation; ASTM D2435 for Cc and cv.

    Worked example

    At the default inputs

    Inputs
    • Layer thickness H (m): 6; Initial void ratio e₀: 0.9; Compression index Cc: 0.3; Initial effective stress σ′₀ (kPa): 100; Stress increase Δσ (kPa): 50; Coefficient of consolidation cv (m²/yr): 2; Drainage: double
    Calculation path
    1. 1

      Stress ratio → 0.176 Settlement → 166.8 mm Time → 3.8 yr

    Result

    Primary settlement: 166.8 mm · Vertical strain: 2.78% · Time to 50 %: 0.89 yr

    Interpreting the result

    A 6.0 m layer with Cc 0.30 settles 166.8 mm under 50 kPa, reaching 90 % consolidation in 3.8 years.

    Assumptions & limitations

    • Stress increase is constant with depth.
    • Secondary compression is excluded.
    • Double drainage halves the drainage path.

    Frequently asked questions

    Why does doubling the load not double the settlement?

    Settlement is logarithmic in stress.

    What if the clay is overconsolidated?

    Use Cr below the preconsolidation pressure; this page uses Cc only.

    Methodology last reviewed 2026-10-23. Results are informational and not financial or engineering advice — see our disclaimer.