A project was initiated by SKB and Forcit Sweden AB to investigate blast damage from emulsion explosives in two experimental tunnels in Äspö HRL. The new tunnels were excavated with emulsion explosives (Kemitti 810) and charging was done with a Forcit charging unit model 201. Extensive documentation of the excavation works was conducted, so that charge concentration per hole is traceable in contour, floor and helpers. Contour and floor holes were charged with concentration 0.35 and 0.5 kg/m respectively. In order to study blast fractures, five slots were excavated in the wall and floor. The results from mapping of the slots shows a longest blast fracture of 24.5 cm for the 0.35 kg/m charge and 24.1 cm for the 0.5 kg/m charged holes. Generally, there is a large spread in the results with few fractures longer than 20 cm.
SKBs Hard Rock Laboratory (HRL) at Äspö, Sweden, was constructed in the early 1990s down to the level – 450 meter. The facility is used for research and development related to the planned repository for spent nuclear fuel. The Äspö HRL was expanded in 2012 in order to create room for additional experiment sites in the facility. New tunnel were excavated on the -410 and – 450 m levels. The new tunnels were excavated using pump emulsion explosives (Kemitti 810) and charging was conducted using a Forcit charging unit model 201 with a hose feeder for the string charged hole types.
Much effort was invested in the control program for the Äspö HRL Expansion Project for follow up and documentation of the excavation works. Documentation of the blasting works included extensive follow up on drilling and charging precision for each hole with aid from field notes and logger data, see Ittner et al. (2014) and Ittner & Christiansson (2014).
The well documented tunnels included in the Äspö HRL Expansion project are well suited to study blast damage from string emulsion and a project was initiated by SKB and Forcit Sweden AB. In total five rectangular slots were excavated in the floor and wall of the two new experimental tunnels TASN and TAS04 during November 2014. Figure 1 depicts the locations of the five slots at the -410 m level in Äspö HRL.
