The gathering of milling data relating to some thousands of metres of pipe laid in Italy with microtunnelling technology has permitted a study to be commenced, based on energy criteria, which aims at the “a priori” determination of the degree of difficulty of drilling in relation to the type of soil.

The “specific drilling energy” parameter is determined as a concise, easily understood datum, able to summarise the most significant parameters and their relation to the characteristics of the soil traversed.

A preliminary result of the study allows a summary classification of the types of soil relative to the average specific energy required in the drilling.