PUSHING MACHINES

Penetrometer. The fastest way of inserting the blade, if the soil is penetrable, i.e. obstacle-free, is using a 10 ton or 20 ton penetrometer. Truck mounted penetrometers are very effective, but anchored penetrometers, less expensive, are also conveniently used. The advancing speed may be 2 cm/sec, as in the CPT, but speeds twice or half the 2 cm/sec are adequate because, unlike CPT, the penetration is just a means of advancing the blade. The real test occurs later.

 

Drill Rig – Torpedo method. When using a drill rig, generally the torpedo method is adopted. It consists in composing a torpedo typically 3 m long, ending with a DMT or SDMT probe, and advancing it from the bottom of a borehole. Then the torpedo is extracted, the penetrated length of borehole cleaned, and testing is resumed from the new bottom of the borehole (see figures en/ita).

 

Drill Rig – Sciacca method. When using a drill rig the blade can also be advanced by the Sciacca method. In this configuration the cable exits the rods above ground. When the cable exit is near the ground, another push rod is added.

 

 

OTHER METHODS

Dynamic insertion, by means of a drill rig or an SPT tripod. Advancing the blade by percussion, e.g. using the SPT hammer, is also possible. Dynamic insertion is not the preferred way, but in some countries (e.g. Swizterland) driving is the most common insertion method.

 

SDMT can be executed in impenetrable soil (hard soil/ soft rock) in boreholes backfilled with fine gravel (grain size 4 to 12 mm, no fines). See Instrumentation SDMT and Test Specifications SDMT (en/ita).

 

 

Additional information can be found in Section 3 of the TC16 DMT Report.

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