Laboratory studies of dynamic rock fracture and in-situ measurements of cutter forces for a boring machine

Abstract: All forms of rock failure usually happen within a very wide range of loading rates covering static and dynamic loading. Since rock failure always results from fracture - the propagation of one or more cracks- the first part of the thesis is focused on laboratory studies of the influences of loading rates on rock fracture. This part has mainly investigated macro/micro fracture characteristics of rock, energy partitioning in the process of rock fracture, and the influences of high temperatures on rock fracture. In the second part of the thesis, the research has dealt with in-situ measurements of the cutter forces and cutter temperatures of a boring machine. Then a number of core rock samples were taken from the borehole. After that, the cracks induced by mechanical boring were examined by using a scanning electron microscope (SEM). Finally, an approximate relationship between the length of the medium cracks and the respective normal forces measured in-situ was established.