Excavated Disturbed Zones

The near field of the repository includes the engineered barrier system (EBS, i.e., canister and buffer) and the waste form. Also included in the near field is the interface between the buffer and the host rock, denoted as excavation disturbed zone (EDZ). In terms of waste/water interactions, the geochemical evolution of the near field is essential as it controls the composition of the fluids that will eventually contact the waste. 

The AE locations in that time are shown in Fig. 11.11 in a top view (x-y-plane) where the plan of galleries at the 945-m level is overlaid to the map of AE events. All events are located in the excavation disturbed zone (EDZ) close to walls of galleries. Only those walls are indicated by events which are orientated toward the sensor array. 

In conclusion, nearly all events were found in zones close to walls and galleries. These excavation disturbed zones contain many small dilatant microcracks. The width of the zone is about 1 m, measured from the surface of the gallery. Fig. 11.13 clearly demonstrates this fact in a projection parallel to a drift close to the sensor array. For a better orientation the measured profile of the drift is also shown. 

In salt rock, AE activity is detected around open cavities and at the boundaries between different rock types. Creep processes cause high AE activity due to high deviatoric stresses at the walls of the cavities in the excavation disturbed zone. This kind of AE activity is interpreted as ongoing... 

Malmgren, L., Saiang, D., Toyra, X, Bodare, A. 2007. The excavation disturbed zone (EDZ) at Kiirunavaara mine, Sweden—by seismic measurements. Journal of Applied Geophysics 61 1-15. 

Sheng, Q., Yue, Z.Q., Lee, C.F, et al. 2002. Estimating the excavation disturbed zone in the permanent shiplock slopes of the Three Gorges Project, China. International Journal of Rock Mechanics Mining Sciences 39 165-184. 

Sheng, Q. 2003. Excavation disturbed zone of deep cutting rock slopes and mechanics behavior of engineering rock mass. Chinese Journal of Rock Mechanics and Engineering 22(10) 1761-1761. (in Chinese). 

Li, S.J., Yu, H., Liu, YX. and Wu, F.J. 2008. Results from in-situ monitoring of displacement, bolt load, and disturbed zone of a powerhouse cavern during excavation process. International Journal of Rock Mechanics Mining Sciences 45 1519-1525. 

MOTIF was used to predict the hydrogeologic disturbances caused by the excavation of the URL shaft to a depth of 255 m (Davison and Guvanasen 1985). Planar elements were used to represent the fracture zones and 3D continuum elements were used to represent the background rock mass. In general, the predicted drawdown histories agreed well with measurements. Figure 3. The overall trend of... 

With respect to the practical application of these new tools in a radioactive waste disposal in rock, where zones of permeability for fluids are of upmost interest, it is to remark that a sufficient large number of sensors should be arranged in such a way that the focal sphere is well covered in all directions, which is essential for the use of only P-wave first motions for location. This is a question of accessibility for drilling wells for sensor installation. The sensors should be installed far enough from excavations and galleries so that the wave propagation will not be disturbed ("shaded") by excavated rooms and galleries. 

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