ISO 22476-11:2017 establishes guidelines for the equipment requirements, execution of and reporting on flat dilatometer tests.

NOTE This document fulfils the requirements for flat dilatometer tests as part of the geotechnical investigation and testing according to EN 1997‑1 and EN 1997‑2.

The basic flat dilatometer test consists of inserting vertically into the soil a blade-shaped steel probe with a thin expandable circular steel membrane mounted flush on one face and determining two pressures at selected depth intervals: the contact pressure exerted by the soil against the membrane when the membrane is flush with the blade and, subsequently, the pressure exerted when the central displacement of the membrane reaches 1,10 mm.

Results of flat dilatometer tests are used mostly to obtain information on soil stratigraphy, in situ state of stress, deformation properties and shear strength. It is also used to detect slip surfaces in clays. The flat dilatometer test is most applicable to clays, silts and sands, where particles are small compared to the size of the membrane.