SlipSurface IQ Correlation — reference

Inputs

• Groundwater: depth of the water table, γ_w.
• Layers, from the surface down, one row per layer: thickness, granular or cohesive, and what the laboratory measured — gravel and fines contents, LL, PL, w, G_s, γ, γ_sat, e₀, D₁₀ and the unconfined compressive strength q_u. A zero means “not measured”: the program estimates what it can.
• SPT: depth and field blow count N; hammer energy ratio, borehole diameter, sampler, rod above the ground, the C_N rule and its cap.
• CPT(u): depth, q_c, f_s and u₂; the cone's net area ratio a, N_kt and N_Δu.
• V_s: depth and measured shear wave velocity (downhole, crosshole, SCPT, MASW …).
• Selection: how the correlations are combined, E_u/c_u, ν for the exports, and — for any parameter — one correlation to use instead of the combination.

Test tables take a block pasted from a spreadsheet: tab, semicolon, comma or space separated, with a decimal comma where the columns are tab or semicolon separated.

What it computes

Parameter	Correlations
γ, γsat, e0	phase relations; Robertson & Cabal (2010)
Dr	Skempton (1986), Idriss & Boulanger (2008), Meyerhof (1957); Jamiolkowski et al. (1985), Baldi et al. (1986), Kulhawy & Mayne (1990)
φ′	Wolff (1989), Hatanaka & Uchida (1996), Schmertmann (1975); Robertson & Campanella (1983), Kulhawy & Mayne (1990); Kenney (1959), Sorensen & Okkels (2013) for clays
cu	Stroud (1974), Hara et al. (1974), Terzaghi & Peck (1967), Sivrikaya & Toğrol (2006); (qt − σv0)/Nkt, Δu/NΔu; qu/2; Mesri (1975)
σ′p, OCR	Mayne et al. (2002); Kulhawy & Mayne (1990); Stas & Kulhawy (1984)
K0	Jaky (1944); Mayne & Kulhawy (1982)
E′, Eu, M	Kulhawy & Mayne (1990), Bowles (1996); Schmertmann et al. (1978), Robertson (2009); Eu/cu (Duncan & Buchignani 1976)
Cc, Cr, Cα	Skempton (1944), Azzouz et al. (1976), Nishida (1956), Koppula (1981), Wroth & Wood (1978); Nagaraj & Murty (1985); Mesri & Godlewski (1977), Mesri (1973)
cv	k·M/γw from the CPT
Vs, G0	Imai & Tonouchi (1982), Ohta & Goto (1978), İyisan (1996); Robertson (2009), Mayne (2006); measured
k	Hazen (1911); Robertson (2010)

Every correlation is evaluated at each test depth and averaged over the layer; the By correlation view and the report list each one's value, source, number of tests and formula beside the selected value.

Outputs

• Parameters — cards and the selected parameters of every layer; warnings where the CPT contradicts the declared soil, a chosen correlation has no data, or OCR < 1.
• By correlation — every correlation of every parameter, layer by layer.
• Tests — the SPT and CPT as processed: stresses, corrections, normalised values, and the parameters at each depth.
• Figures — soil profile, SPT, CPT(u), Robertson's SBT chart, strength, density and stress history, stiffness, the plasticity chart, and the correlations compared.
• Report — PDF, HTML or Word: inputs, index properties, selected parameters, every correlation, processed tests, figures, warnings, method notes and the references used.
• Exports — SlipSurface IQ Settle and SlipSurface IQ Bearing project files, and the parameters as CSV.

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