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The Marchetti Flat Dilatometer (DMT) consists of a flat blade which is driven into the soil. The blade has a fine circular metal membrane which can be expanded horizontally in the soil using pressurized gas.
The pressure P0 which is needed to start membrane movement is measured, as is the pressure P1 which is required to produce a displacement of 1.1 mm in the centre of the membrane. These two measurements are taken at regular intervals, usually of 20 cm.
The penetration can be carried out statically, by means of a CPT truck, allowing both test methods to be used as part of a single survey campaign, without additional costs.
Sample conservation
As well as being a quick and repeatable test which causes minimal disturbance to the soil, the DMT has the following specific advantages:
- It is a two parameter test, P0 and P1, the first of which gives direct information about the soil tension, a factor which governs soil behaviour.
- The calculation of settlement of shallow foundations is one of the principal applications of this survey, especially when dealing with sands where edometric surveys cannot be carried out.
- It is an excellent test for monitoring ground treatments.
- Compacting is shown by an immediate increase in KD and M, even in the case of slight changes in density.
- Location of surface breakage of slopes in clayey soils.
- P-y curves for piles with lateral load.
- Determination of liquefaction potential of sands.
