Validieren eines Modells zur Beschreibung des Bohrvorganges in Naturstein mit Hilfe von Daten, die mit dem Bohrwiderstandmess- System (DFMS) erhalten / werden Validation of a Model of Rotary Drilling of Rocks with the Drilling Force Measurement System

The degradation of monumental stones is the result of the interaction between the material and environmental factors, such as mechanical loads, moisture, freezing and thawing, heat, atmospheric pollutants and living organisms. This interaction starts at the stone surface and progresses inwards reaching several millimetres in depth. The common decay or degradation processes result in significant loss of the strength properties of the outermost layers of stone material and quite often these exhibit erosion features, a cohesionless appearance and typical disintegration forms. At present there is no method which can measure with sensitivity, reliability and quasi-non-destructively the cohesive properties of stones both at the exposed surface and at larger depths (few centimetres), which can be used both in laboratory and in situ. The objective of this work is to verify the capability of a phenomenological model to characterize the cohesional properties of stones and the influence of wear on drill-bit performance based on appropriate microdrilling measurements performed by using a new portable Drilling Force Measurement System (DFMS).