Pre-Conditioning of Hard Rocks as Means of Increasing the Performance of Disc Cutters for Tunneling and Shaft Construction

摘要

Excavation of very hard intact rock by various mechanized systems is challenging and requires high cutting forces. This refers to tunneling through rock that is in excess of 200-300 MPa. which has also been considered difficult tunneling conditions by the ITA Workgroup 14 that is specialized in mechanical excavation. There are innovative concepts to improve the cuttability of hard and abrasive rocks by using pre-conditioning systems for introducing micro-fractures in the rock. This includes high-power microwave irradiation which leads to weakening of the rock by introducing micro fractures in the medium. The initial results of treating rock surface with a 24 kW microwave shows initiation of some micro-crack network and the preliminary results will be discussed in this paper. The findings will be linked to possible improvements of tunnel/shaft boring machines (TBM, SBM) performance, especially with respect to possibility of deploying a hybrid system to aid the center and gage cutters by pre-damaging the rock.