Design, Use, and Interpretation of an Instrumented Flat Dilatometer Test

The flat dilatometer test (DMT) has been increasingly used as a routine geotechnical site characterization tool in numerous parts of the world for over 30 years. In the meantime, with the rapidly growing metal 3D printing technique, engineers now can design robust, durable devices that are impossible to make by traditional means. This paper presents the development of an instrumented dilatometer that has continuous measurements of a piston expansion up to 2035 mm and pore pressure at the piston center with the assistance of a metal 3D printing technique. A field-testing program consisting of an instrumented flat dialtometer test (iDMT), a DMT, and a cone penetration test (CPT) positioned 1 m apart from each other was carried out in a site in Belgium composed of soil that ranged from silty sands to sandy silts. Interpretation techniques are provided to evaluate the test results, such as the conceptual contact pressure based on the full pressure-dispalecement curve in the DMT as an alternative for po in the DMT. The pressure required for a 0.56 mm piston expansion is found to be equivalent to that of a 1.1 mm central membrane displacement, based on a finite element method (FEM) simulation apporach with teh assumption of linear elastic soils and a modified displacement boundary. A comparison made between test results from the iDMT, the DMT and the CPT shows reasonable trends and suggests the use of the iDMT in future soil investigation.