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Characterisation of the hydraulic properties of fractured rock from grouting data

Gunnar Gustafson (Institutionen för bygg- och miljöteknik, Geologi och geoteknik) ; Christian Butron (Institutionen för bygg- och miljöteknik, Geologi och geoteknik) ; Åsa Fransson (Institutionen för bygg- och miljöteknik, Geologi och geoteknik)
Toyama, Japan-IAH 2008 Toyoma: Integrating Groundwater Science and Human Well-Being (2008)
[Konferensbidrag, refereegranskat]

Pre-grouting of tunnels produces a large amount of data that so far has been of little use to analyse and characterize the properties of the rock. A fan of grouting boreholes is drilled ahead of the tunnel to excavate. In the boreholes water pressure tests (WPT) are made before grouting. After grouting control holes are drilled where new WPTs are performed. These data can give new information on the hydraulic structure of a fractured crystalline rock. The methods and findings are demonstrated for a test segment of a newly constructed railway tunnel, the Nygård tunnel. The paper shows also how the WPT data can be used to assess the characteristic size of the conductive fractures and channels from the WPTs before and after grouting. The interpretation is that there is a system of conductive fractures, which are relatively easy to fill with grout. They are connected by a network of less pervious channels, which make up low permeability connections between the conductive fractures. They are difficult to intersect by a borehole and are thus difficult to grout. Finally the findings support a conceptual model of the rock as a system of sparse conductive two-dimensional fractures connected by much less conductive one-dimensional channels.

Nyckelord: Groundwater in hard rocks, hydraulic properties of the fracture system, connectivity of the fracture system

Denna post skapades 2008-12-23. Senast ändrad 2012-05-22.
CPL Pubid: 82764


Institutioner (Chalmers)

Institutionen för bygg- och miljöteknik, Geologi och geoteknik



Chalmers infrastruktur

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Drip Sealing Grouting of Tunnels in Crystalline Rock: Conceptualisation and Technical Strategies