Soil Mechanics & Lab Tests

CPT Soil Behavior Type (SBT) & Correlation Calculator

Classify soil behavior type (Robertson 1990/2016) from CPT cone resistance (qc), sleeve friction (fs), and pore pressure (u2), with live SBT chart and correlations for su, φ', and N60.

Robertson (1990, 2016)ASTM D5778ISO 22476-1

Inputs

Demo

CPT Sounding & Stratigraphy Inputs

Depth (z, m)

Cone Resistance (qc, MPa)

Sleeve Friction (fs, kPa)

Pore Pressure (u2, kPa)

Water Table Depth (dw, m)

Unit Weight (γ, kN/m³)

Net Area Ratio (a)

Cone Factor (Nkt for su)

Results

Theory and formulae

Theory & Formulae (CPT SBT)

About this calculator

This free cpt sbt classifier calculator runs entirely in your browser: what you enter is never uploaded. Use the calculation steps and the theory section to check the working, and print a calculation sheet with the inputs, results and formulae for your records.

Methods and references: Robertson (1990, 2016), ASTM D5778, ISO 22476-1.

Topics: cpt, cptu, robertson, soil behavior type, sbt, sbtn, friction ratio, cone resistance, undrained shear strength, friction angle, spt n60.

Engineering notice: Results are for preliminary estimation, screening and education. All inputs and outputs must be independently verified by a qualified professional engineer before use in any design or construction decision. Read the full disclaimer