Géptest

Géptest is a term used in some francophone geotechnical literature to describe a family of in-situ tests designed to determine the geotechnical properties of soils and rocks on site. The term combines geo- (earth) with test and is used to distinguish field testing from laboratory analyses.

Definition and scope: Géptest refers to laboratory-like assessments performed directly at the site to evaluate bearing capacity, stiffness, shear strength, porosity or permeability, and stratigraphic information, as well as groundwater conditions. The precise methods vary by region and discipline.

Common methods include plate load tests, standard penetration tests (SPT), cone penetration tests (CPT), vane shear tests, and measurements of in-situ density, moisture content, and pore-water pressure. Some workflows also incorporate dynamic probing, seismic refraction, or light point load tests.

Procedure and interpretation: Tests are typically conducted with portable rigs or boreholes. Data are interpreted with empirical correlations, calibration against known soil types, or finite-element based back-calculation to estimate properties used in design.

Applications: Géptest data inform foundation design, earthworks, slope stability assessments, tunnel and dam projects, and ground improvement planning.

Limitations: Results can be influenced by soil heterogeneity, weathering, disturbance during sampling, inflow conditions, and operator expertise. Cross-validation with laboratory tests and multiple field methods is common.

See also: Geotechnical engineering; In-situ testing; Standard Penetration Test; Cone Penetration Test; Plate load test; Vane shear test.