How does the Cone Penetration Test (CPT) work and what information does it provide?

CPT pushes an instrumented cone at constant rate (20mm/s) measuring tip resistance (qc), sleeve friction (fs), and pore pressure (u2 for piezocone). Friction ratio (fs/qc) helps identify soil type: low values indicate sand, high values indicate clay. CPT provides continuous soil profile, detects thin layers missed by SPT, and gives more repeatable results. Data is correlated to shear strength, relative density, and soil behavior type using classification charts (Robertson). Piezocone dissipation tests give consolidation properties.