A dilatometer test (DMT) consists of pushing a flat blade located at the end of a series of rods. Once at the testing depth, a circular steel membrane located on one side of the blade is expanded horizontally into the soil. The pressure is recorded at specific moments during the test. The blade is then advanced to the next test depth, typically in 20 cm steps.
The seismic dilatometer (SDMT) is the combination of a dilatometer blade with an add-on tubular element equipped with two sensors, for measuring the shear wave velocity Vs.
The test can be executed in soils from semiliquid to soft rock, composed of soil grains small compared with the membrane diameter (60 mm).
The Seafloor DMT is a penetrometer for advancing the DMT, the SDMT and the Medusa DMT with multiple short length strokes (0.10 m or 0.20 m). It is very cost-effective compared to competitive devices because it does not require to advance the probe at a specific speed (2 cm/s for CPT).
DMT provides estimates of the oedometer modulus M, shear strength Su, OCR and Ko in clay, liquefaction resistance CRR.
The DMT parameter KD is considerably more sensitive to Stress History than other in situ tools. Stress history is important, as it significantly increases moduli and liquefaction resistance. If Stress History is not felt, its benefits are wasted, leading to an uneconomical design.Read More