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SKB Apsö UFM application

Project Description

SKB asked ITASCA to apply an advanced modelling framework (UFM) on the Äspö site to estimate its consistency with structural and hydraulic data.

Itasca's Role

The UFM modelling framework (detailed in Davy et al., (2010, 2013)) is used to assess fracturing parameters and improve the DFN models in Äspö using in‐depth data.

In practice a given set of DFN model parameters is initially related to the spatial volume position and relative dataset from which it is derived. We use both borehole logs and trace mappings along the Äspö tunnel (Figure1).

The UFM relevancy is assessed through the analyses of fracture densities, trace size distributions (Figure 2) and T terminations statistics.

Project Results

We predict a transition scale between a sparse regime (where fractures do not interact) and a dense regime (where fracture organization is governed by fracture‐to‐fracture interactions) between 5 and 10 m.

Project Image(s)

Overview of datasets from the Äspö area
Trace size distributions from Äspö tunnel data


Davy, P., R. Le Goc, and C. Darcel (2013), A model of fracture nucleation, growth and arrest, and consequences for fracture density and scaling, Journal of Geophysical Research: Solid Earth, 118(4), 1393‐1407.

Maillot, J., P. Davy, R. Le Goc, C. Darcel, and J. R. de Dreuzy (2016), Connectivity, permeability, and channeling in randomly distributed and kinematically defined discrete fracture network models, Water Resources Research, 52(11), 8526‐8545.


Itasca Consultants S.A.S.


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