Databank

Databank

Posiva publishes Working Reports and Posiva Reports. From the year 2006 nearly all the reports have been published on our webpage and they can be found in the databank. In the databank you can also find our Annual Reviews and some other publications as well. You can also find print-quality pictures and useful links in the databank.

Recent publications


Workreport 2018-3

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Name:

Development of Shaft Grouting Methods During the Construction of ONKALO Research Facility at Olkiluoto

Writer:

Hatakka, L., Salminen, N., Tirinen, J.

Language:

English

Page count:

104

Summary:

Posiva Oy is preparing for the final disposal of spent nuclear fuel of its owners in crystalline bedrock in Finland. Olkiluoto in Eurajoki has been selected as the site for the repository, subject to further detailed characterization, including an underground rock characterization and research facility, ONKALO. During the repository operation the open tunnels and shafts of the ONKALO, and the subsequent repository, are likely to create a hydraulic disturbance to the site’s groundwater flow system.

The bedrock is generally sparsely fractured, but features some hydraulically conductive fracture zones that contribute significantly to inflow. Two of these, HZ20A and HZ20B intersect both the access tunnel and all of the shafts below the shaft niches at level -290 m.a.s.l.

Grouting of the shafts has been done in several phases and development of the grouting methods during the work has been ongoing. This report gives a detailed account of the development and results of the grouting of the shaft interval at -290 to -437 m.a.s.l. and a brief overview of previous development related to grouting in ONKALO.

The grouting methods developed much during the several grouting phases: improvements in recipe of cement grouts, grouting phases and the positioning of grouting holes, and later the use of silica grout were made to ensure an exceedingly low inflow in the raise bored shafts in the shaft interval which was critical for the repository.

After raise boring the shafts grouted with silica sol had 50 to 80 % less inflow than the exhaust air shaft, which had been grouted with cement-based grouts only.

Keywords:

Shaft, grouting, silica grouting of shafts, cement grouting of shafts, washing fractures, development of grouting, silica grouting, colloidal silica

File(s):

WR 2018-03_web (pdf) (14.9 MB)


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