关键词 钻 钻井 钻头 磨损率 销毁工作 各向异性 联合间距 石英所含之物 孔隙
Drillability prediction: geological influences in hard rock drill and blast tunneling
Abstract Usually the main subject in preliminary site investigations prior to tunnelling projects is the prediction of tunnel stability. During the past years in conventional drill and blast tunnelling, problems have
occurred also connected to the accurate prediction of drillability in hard rock. The drillability is not only decisive for the wear of tools and equipment but is —along with the drilling velocity — a standard factor for the progress of excavation works. The estimation of
drillability in predicted rock conditions might bear an extensive risk of costs. Therefore, an improved prediction of drilling velocity and bit wear would be desireable. The drillability of a rock mass is determined by various geological and mechanical parameters. In this report some major correlations of speciÞc rock properties and especially geological factors with measured bit wear and drilling velocity are shown. Drilling velocity is dependent on a lot of geological parameters: Those principal parameters include jointing of rock mass, orientation of schistosity (rock anisotropy),degree of interlocking of microstructures,porosity and quality of cementation of clastic rock,degree of hydrothermal decomposition and weathering of a rock mass. Drilling bit wear increases with the equivalent quartz content. The equivalent quartz content builds the main property for the content of wearrelevant
minerals. For various groups of rock types di¤erent connections with the equivalent quartz content could be detected. In sandstone bit wear is also dependent on porosity or the quality of the cementation. Finally, an investigation program is submitted,which helps to improve the estimation of rock drillability in planning future tunnel projects.
Key words Drillability• Drilling rate •Bit wear•Destruction work• Anisotropy •Joint spacing•Equivalent quartz content • Porosity