Hammer

The intact rock strength of a rock mass has been determined by several different means in the context of research for slope stability assessment. The intact rock strength was determined with unconfined compressive strength testing, Schmidt hammer, Equotip, and estimation by so-called ‘simple means’. Estimation by ‘simple means’ denotes estimating the intact rock strength by hammer blows, crumbling by hand, etc. Many different people to avoid observer bias have done hundreds of assessments of intact rock strength by different means on the same rock masses. The results show that in many cases an estimation of intact rock strength by ‘simple means’ is more representative for establishing the intact rock strength of a rock mass than establishing the intact rock strength by more elaborate testing.

A hammer-string interaction for bass notes is investigated and the problem what can cause the hammer to rebound is clarified. For a linear elastic hammer interacting with a long flexible string the exact solution of the equation describing the hammer motion is derived. It was shown that in some cases no reflected wave is needed to assist the hammer for going away from the string. The numer-ical simulation carried out for the first ten hammers and strings of Parlour Grand Piano shows that the real hys-teretic hammer leave the string before the string begins pushing back on the hammer.

The intact rock strength of a rock mass has been determined by several different means in the context of research for slope stability assessment. The intact rock strength was determined with unconfined compressive strength testing, Schmidt hammer, Equotip, and estimation by so-called 'simple means'. Estimation by 'simple means' denotes estimating the intact rock strength by hammer blows, crumbling by hand,