Measuring of Over-Break and the Excavation Damage Zone in Conventional Tunneling
During tunnel excavation, blast induced damage or Excavation Damage Zone (EDZ) interacts with existing geological structure of the rock-mass. This can and cause over-break and stability issues during and after excavation. Today the EDZ is determined by correlation-based methods, although direct measurement is possible. This paper presents investigation methods for EDZ quantification during excavation. The discussed methods are applied in the Stockholm By-Pass project. The literature review and the case study applications are summarized in a comprehensive table with benefits and limitations of the different investigation methods. The methods discussed can be used to achieve a better quality of the tunnel contour, especially the direct investigation techniques. The EDZ can be reduced by adjusting the blasting plan, specific charge as well as improving the quality of the drill and blasting procedures.