Fracturing of hard rocks by microwave treatment and potential applications in mechanised tunnelling

Extremely hard and abrasive rocks have posed great challenges to mechanical excavators such as tunnel boring machines and roadheaders by increasing the cutter wear and decreasing the penetration rates. Microwave treatment prior to mechanical rock breakage has been recognised as a promising technology. This PhD project measures/derives the dielectric properties of commonly encountered rocks and minerals and investigates the effect of microwave treatment on the physical and mechanical properties of three igneous rocks (gabbro, monzonite and granite) using a 2 kW single-mode microwave system. Experimental results indicate that microwave can effectively and efficiently weaken hard igneous rocks by generating macro/micro cracks in the heterogeneous rock matrix. The thesis also discusses the technical considerations of using microwave on tunnel boring machines in the field.