| Abstract: | The choice between drill-and-blast vs mechanical boring methods is often not obvious. Several factors may have a decisive influence on this choice-e.g. the geometry and length of the tunnel, site conditions and borability of the rock. Both the unconfined compression strength and the joint distance have a considerable influence on the net penetration rate. Site conditions, rock quality and water conditions influence the utilization of the tunnel boring machine. The drill-and-blast method is normally less sensitive to deviations from assumed ground conditions. |
