Punch Penetration Index
The punch test is a nonstandard laboratory test that was originally designed to provide a direct method for estimating the normal loads on button and disc cutters during mechanical excavation of rock. It has been used as a tool for estimating Tunnel Boring Machine penetration rates. The test has been also used to evaluate certain rock characteristics such as brittleness, bedding or cleavage, and porosity. A tungsten carbide indenter is pressed into a saw cut rock sample that is confined by a steel ring. During the test the rock fails by crushing and chipping. The load on the indenter and its depth are recorded to produce a plot of force versus penetration.
A minimum of 4 in of core
Punch Penetration, Tunnel Boring Machines, Penetration Rates