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Grouting and Analyses of a Fracture in Äspö HRL, Characterisation, grouting and verification of grouting results for silica sol

Johan Funehag (Institutionen för geologi och geoteknik, Teknisk geologi)
Göteborg : Chalmers University of Technology, 2004. - 60 s.
[Rapport]

This report is part of the project “Non-cementitious low-pH injection grout for smaller fractures” that is a sub-project under the main project “Injection grout for deep repositories”. The project is financed by SKB (Sweden), Posiva (Finland) and NUMO (Japan). The sub-project objective is to find a grout that can be used to grout fractures with a hydraulic aperture less than 100 μm and that fulfills environmental and long-term safety demands. This report describes a field test conducted during spring 2004 in a pillar located in the main tunnel at Äspö HRL at a depth of around 100 m below the surface. Previous studies (Fransson, 2001) show that the fracture of interest is found in a section 2.0-2.5 m in a borehole drilled parallel to the main tunnel. The transmissivity is around 5x10-8 m2/s corresponding to a hydraulic aperture of approximately 40 50 μm. The fracture has earlier been grouted with cement which resulted in a penetration length of around 0.1 m around the grouted borehole (Eriksson, 2002). The fracture was grouted with a silica sol, produced by Eka Chemicals, Bohus under the name Eka® Gel EXP36. It consists of extremely small amorphous silica particles suspended in water. The accelerator used was a salt solution, CaCl2 (2,9%). The pH is around 10. The grout was also mixed with optical brightener to make it possible to see the grout using UV-light. The grouting design was determined using the hydraulic aperture analysed by Fransson, 2001. Three methods were used to determine the penetration length and sealing efficiency; namely detection of grout in 6 cores using UV-light, analysing part of the grouted fracture in microscope and using hydraulic tests. The results show that five of totally six cores had traces of silica sol, which would indicate a penetration length of at least 1 m in the fracture. The microscopy analyses verify that silica sol were apparent in the fracture but not completely filled. The achieved penetration length of 1 m was compared with 2-D mathematical model. The results show that the model underestimates the penetration length with 0.25 to 0.35 m. The hydraulic tests result in a sealing efficiency of the silica sol grouting in the affected rock mass of 70%.

Nyckelord: Grouting, Gelling liquids, Silica sol, Colloidal silica, Penetration length, Hydraulic test



Denna post skapades 2006-08-25.
CPL Pubid: 3028

 

Institutioner (Chalmers)

Institutionen för geologi och geoteknik, Teknisk geologi (2003-2004)

Ämnesområden

Geovetenskap och miljövetenskap
Samhällsbyggnadsteknik

Chalmers infrastruktur

Ingår i serie

Publ. B - Chalmers tekniska högskola, Geologiska institutionen 2