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3.3 TREPORTI (VENICE, ITALY) (JULY 2001)

As a matter of experimentation, one vertical CPTWD, was carried out down to 110 m, in mainly sandy zonę, starting from 50 m.

Due to very high resistance of the sand (sometimes Q_c greater than 50 Mpa) , some intervals were carried out at continuous core drilling (also in order to verify and calibrate the static test) and non coring drilling with MWD.

In order to keep a constant ratę of penetration, having high density sandy intervals, the Operator sometimes increased the pressure of the mud injection at intervals in order to allow a 2 cm/s ratę (Ref 5 ). Therefore, in order to evaluate the potential effects of such pressure in the penetrometric parameters, another pressure sensor has been added to the current model, just above the friction sleeve ("U3" according to the recent nomenclature).

The diagram below shows the penetrometric graphic (Qc, Fs, U, F_r) from 0 to 110 m.

4 COMMENTS ON THE RESULTS

Actually, the amount of current available data to be compared with CPTWD is relatively smali and at present, comparative tests with other testing methods have not been carried out.

Accordingly, it would therefore be necessary, to perform a morę extensive validation of the obtained results with the following procedures:

*    To execute comparative tests with CPTU and CPTWD at a depth which is achievable by the normal penetrometers. Such tests should be carried out in different types of soils in order to establish the correct testing procedures, in terms of the length of the cone, thrust calibration, pressure and volume of the injected fluid.

*    To establish the cone’s optimum length below the drill-bit by testing in different types of soil also at great depth, analyzing the variations of U2 and U3 as