Geologisch-geotechnische Einflussfaktoren auf die Bohrbarkeit bei Bohrpfählen in Festgestein

Abstract

Evaluation of geological and geotechnical influencing factors on drillability in hard rock – A practical assessment

While drillability in tunnelling is a well-researched topic, the importance of drillability for rotary pile drilling has commonly lacked recognition. This report is aimed at shedding light on the systematic evaluation of drillability in bored piles, a topic which can be of paramount importance for the successful completion of any construction project. The main focus is on the correlation of geological and geotechnical influencing factors on drillability, which is examined in various case studies. The analyses of the case studies show that geological and geotechnical influencing factors have a significant impact on the achievable drilling velocities and tool wear. The working principles and drilling performance of the round shank chisels and replaceable teeth are analysed separately, as notable differences were evident for these different tools, especially when taking rock mass properties into account. Based on these results, rotary-piling specific classification systems for tool wear were developed –with the one for replacement teeth being first of its kind. The presented approaches contribute to a stronger consideration of drillability-related factors and key challenges in construction practice—starting from the very beginning of a project as a decisive planning parameter, rather than recognizing drillability as a critical bottleneck during the construction phase.