ABSTRACT: The Boreability Index (IB) is a measure of the full face boreability of the rock mass. The index IB can be calculated in two ways depending on the application. In a boreability model the index IB used is the quotient between net penetration rate and the two machine parameters cutterhead revolution speed and thrust per disk cutter. In a prediction model IB consists of data from an indentation test (modified Handewith test) and a factor for joint and weakness planes.
By applying the boreability model to measurement while boring data, it is possible to detect important changes in the rock mass during the boring process, e.g. fracture zones and different rock types. This model maybe also can be a helpful tool when mapping the tunnel and in planning of reinforcements after boring. In our opinion IB is more sensitive measure of the rock mass parameter than the net penetration rate.
