The Flat Plate Dilatometer (DMT) is an in situ test for the determination of various key soil parameters used for geotechnical design.
The test is rapid, accurate, simple and cost effective. The results are highly repeatable and independent from the operator.
The blade may be advanced with any field machine, including CPT rigs and drill rigs.
DMT measurements are performed in situ, directly on the soil in its original position and state. This eliminates the disturbance caused by drilling, sampling, transportation to the laboratory and sample preparation at the laboratory.
At each test depth, a circular steel membrane located on one side of the blade is expanded horizontally against the soil. The pressure readings are recorded at specific moments during the membrane expansion. The blade is advanced to the next test depth, typically with 0.20 m depth interval.
DMT result profiles are available in real time during the test execution.
The direct measurement of soil deformation enables accurate estimations of elastic modulus.
The KD parameter provides stress history information of the soil, a very difficult property to assess with other testing methods.
The Medusa DMT is aa automated Dilatometer probe able to autonomously perform dilatometer tests, which generates and measures the pressure directly at depth. The obtained DMT readings are extremely repeatable, because the fluid is liquid (incompressible) and the pressure regulation is electronically controlled. New test procedures are possible, such as high resolution dissipation tests and horizontal pressure measurements during penetration.
A rechargeable battery pack powers an electronic board, connected to a pressure transducer and to a custom designed motorized syringe. The operator controlled software in the electronics activates the motorised syringe for generating the pressure required to obtain the DMT readings. The maximum operating pressure is 100 MPa. A high accuracy pressure transducer is used to measure the pressure generated by the syringe and operating on the membrane. An electric wire provides the contact status of the membrane to the electronic board. The A, B, C pressure readings are recorded by the Medusa software.
IGS operate the Medusa DMT with an electric cable running from a computer laptop at ground surface down to the probe at depth. In this configuration, the operator may activate the measurement cycle from the computer as soon as the test depth is reached. During the cycle all automation parameters, such as the battery status, the voltage and current provided to the engine, the position of the piston of the motorized syringe, the probe inclination and other additional information, are available in real time. The DMT parameters, in particular the current pressure and membrane contact status, are displayed in real time during the measurement, as for the traditional DMT pneumatic technology.
For the Medusa DMT the firmware embedded in the electronic board implements the procedure for inflating and deflating the DMT membrane. The hydraulic pressurization of the motorised syringe actuates a volume controlled expansion of the membrane, which enables to impose a programmable timing for achieving the readings. Therefore the Medusa DMT is capable to perform dilatometer tests with the recommended timing suggested in the international standards. At the same time, the highly accurate and repeatable time-for-reading facility provided by the instrument prompts for its potential use for performing dilatometer tests adopting variable pressurisation rates in intermediate soils.
Advantages of The Medusa DMT
The Medusa DMT has several advantages over the traditional pneumatic equipment, both in terms of simplification of the probe and test procedure, and in terms of increased accuracy of the measurements (Marchetti et al. 2019).
The major advantages are listed here below:-
Our DMT and Medusa DMT equipment has been developed and supplied by our good friends at Marchetti - Please follow the link to visit the Marchetti Official Website
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