DMT is executable in penetrable materials. The DMT is suitable for sands, silts and clays, where the grains are small compared to the membrane diameter (60 mm). Testable soils range from extremely soft soils (Cu = 2-4 kPa, M=0.5 MPa) to hard soils/soft rocks (Cu = 1 MPa, M=400 MPa). The test is not suitable for gravel, however the blade is robust enough to cross gravel layers of about 0.5 m thickness.

Fig. 1 shows an example of DMT results obtained in hard soils.

S. BARBARA (Arezzo-Italy)

Testable Soils

Fig. 1. Example of DMT results obtained in hard soils.

 

It is noted that the upper limit of the hard soils is not imposed by the DMT blade, that can safely withstand 25 tons (see Figure), but by the capacity of the pushing machine, that rarely exceeds 20 ton.

The figure below is just for illustrating the strength of the blade – not, obviously, for illustrating DMT testing in concrete or rock.

testable-soils-2

As to semiliquid soils (e.g. Fig. 3), the balance of zero (null method), on which DMT is based, permits to obtain accurate results.

However, when testing semiliquid soils, the test procedure must be followed scrupulously (see DMT execution in semiliquid soils). Small errors, unimportant in medium to hard soils, become important when the readings are small.

testable-soils-3

Fig. 3. Example of DMT testing in semiliquid soils results obtained in hard soils.

testable-soils-4

Fig. 4. Example of DMT results in soft soils. Repeatability of the results in two adjacent DMT soundings.

An example of testing in semiliquid soils is described by Huang 2006. DMT readings were taken in the bottom mud of a reservoir 60 to 80 m below water.

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