(GRS 504) Observations of Hydraulic and Transport „Skin Effects“ - SKB Task Force Workshop Prague 2016

K.-P. Kröhn, B. Lanyon

This report provides a synthesis of the contributions and subsequent discussions at the SKB Task Force (GWFTS) “Skin Workshop” held as part of Task Force Meeting #34, in Prague, 9-12th May 2016. It has been produced to provide a database of relevant observations regarding the “skin effect”. For the purposes of the workshop the suggested definition for “skin effect” was:
A reduction of flow or diffusive solute transport in the immediate vicinity of tunnels and boreholes in crystalline rock (also called “geotechnical openings”) as a consequence of excavation and drilling, respectively.
We have split the material presented into flow-related and transport-related observations. For the most part flow observations relate to reduced flow in fracture systems, while transport observations relate to differences in diffusivity or sorption in the rock matrix. Within this document we have further classified observations according to spatial scale and temporal scale.
In bringing these observations together we hope to spread awareness of skin effects and the existing literature concerning them.