APPLICATIONS

The following are possible cases where the use of the CPTWD system could be competitive compared with the traditional type of survey:

• Geotechnical deep drilling (in particular the OFFSHORE drillings) where the cost/production ratio is important.

• DEEP TESTING for special structures and deep foundations

• in all cases where is requested a continous CPTU profile and a standard penetrometer is not usable

• Sites with alternating layers of non penetrable soil (i.e. gravel, cemented sands) and penetrable intervals of geotechnical interest.

• Presence of compact overburden with subsequent penetrable layers.

• Unavailability of the static penetrometer rig, providing the possibility to carry out static penetrometric tests with any kind of drillrig

• Geotechnical and environmental deep drillings: - at the end of the c.c.drilling/CPTWD, it is possible to install a piezometer and/or geotechnical instrumentation inside the bored hole.

• Deep surveys and main presence of sandy soils in which it is not possible to withdraw sufficiently undisturbed samples and the normal tests in situ (i.e. SPT) would not be economically efficient or reliable.

• The opportunity to have a more complete data matrix than with a normal penetrometer, which allows other kinds of interpretations. In particular, the fact of having in the same row (every 2 cm) the data of: Qc, Fs, U2, U3, thrust, torque, rate of penetration, RPM, volume of injected fluid.

 

 

Still, with the idea of adapting other instruments to a core barrel wire-line, are in progress some applications complementary to the CPTU test, for example:

• down hole wire-line field vane test (WIRELINE VANETEST)

• DMT (dilatometric) tests: the implementation of an application of a down-hole wire-line electronically operated Marchetti's dilatometer (WL MEDUSA)

• execution of tests with Permeameter and sampling of fluids. Such applications has already been performed by NGI (Norwegian geotechnical institute) for the execution of offshore tests: a wire-line application of a Permeameter and gas sampler at great depth (D.G.S.: deep gas sampler) has been implemented by the NGI essentially for the petroliferous/oil drilling, but it is also applicable at shallow depth and is based on the same operating principle as the BAT/GEON.

• It is possible to adapt other types of sensors to the cone, i.e. sensors measuring chemical parameters.

• From a theoretical and interpretative point of view, the use of the CPTWD in soft soils, together with the MWD, will allow one to correlate, in a more efficient way, the mechanical characteristics of such soils with the data obtained by monitor while drilling tecnique.

• With the help of the right interpretative and mathematic models it might be possible to extend correlations which were found for soft soils also to coarse or rocky non penetrable soils.

The future improvements of the CPTWD system will include a combination between a drill rig and a pushing system of penetrometric type, possibly anchored in the ground (or to the floating craft in the case of offshore tests) for a higher capacity of pushing. This will allow a better control of the drilling parameters, leaving to the drill-rig the unique task of rotating the drillstring and injecting the mud.