SlipSurface IQ Correlation

Foundations

Soil parameters from tests

Soil parameters layer by layer from laboratory tests, the SPT, the CPT(u) and measured Vs through 57 correlations, with the scatter of each beside it; the parameters go straight on to Settle and Bearing.

Runs in

The browser, app.slipsurface.dev

Plan

Free · free

Languages

English, Turkish

Open in SlipSurface IQ ↗PlansReference

A borehole — its layers with what the laboratory measured, its SPT blow counts, a CPT(u) sounding and any measured shear wave velocities — is turned into the parameters a design needs, layer by layer, through the correlations of the literature:

1. Index — PI, LI, the phase relations (e₀, γ, γ_sat) and the USCS group.
2. Stresses — σ_v0, u₀ and σ′_v0 at every test depth.
3. Field tests — the SPT corrected to N₆₀ and (N₁)₆₀; the CPT(u) normalised to Q_tn, F_r, B_q and the soil behaviour type index I_c (Robertson 2009).
4. Correlations — 57 of them, for γ, γ_sat, e₀, D_r, φ′, c_u, σ′_p, OCR, K₀, E′, E_u, M, C_c, C_r, C_α, c_v, V_s, G₀ and k, each applied only to the soils it was written for.
5. Selection — one value per parameter and layer: from the correlation you choose, or all of them combined by the median, the mean or a cautious estimate (Schneider 1997), with the spread of the correlations beside it.

The parameters go straight on to SlipSurface IQ Settle and SlipSurface IQ Bearing as their project files, or out as a CSV table.

Screenshots

The selected parameters of every layer

Soil profile and selected parameters

Open it

SlipSurface IQ Correlation runs in the browser as part of the online SlipSurface IQ suite. It is on the Free plan.

Open SlipSurface IQ ↗

A word of caution

Correlations are empirical, and their scatter is often a factor of two. What this program gives is a documented first estimate, to be checked against the site's own tests and engineering judgement.

Next steps

• Reference — inputs, the correlations used and the outputs.
• Theory — the formulas, their limits and the full references.