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A platform for research: civil engineering, architecture and urbanism
Grouting Experiences in Underground Research Facility Onkalo, Eurajoki, Finland
A Finnish company, Posiva Oy, is responsible for the research and management of the spent nuclear fuel from the Finnish nuclear power plants. Posiva Oy is constructing an underground research facility ONKALO, which is planned to be a part of the deep repository for high level nuclear waste. ONKALO has reached the depth of about -440 m. The construction started 2003 and the repository will be in use 2020. ONKALO is located in crystalline bedrock of which the fracturing properties, groundwater pressure and groundwater chemistry vary a lot with place and depth. The target for groundwater inflow is < 80 l/min in total for ONKALO (absolute acceptable maximum is 140 l/min). There are also local targets for major water conductive fracture zones. At the same time there are limitations for acceptable materials. The grouting materials have been studied and developed within several international R&D projects. During the tunnel driving, probe holes have been systematically bored and investigated by traditional water loss measurement and by Posiva flow log -device. Besides these, core drilled pilot holes have been drilled in places as the access tunnel has proceeded. In these holes detailed investigations have been done. These holes have produced much valuable data for grouting design. The grouting result has been controlled by measuring the groundwater inflow into the tunnel and by mapping of the leakage areas. The strict targets set for water inflow have been reached, except locally when the fracture zone HZ20 was intersected at the depth of ~300 m. When the access tunnel was about 4500 m long and three shafts were raise bored to the depth of -270 m, the total inflow was ~31 l/min. In the first 500-1000 m of the access tunnel, fracturing was quite dense and fracture apertures were reasonably large for the use of cement-based grouts. The first 1 km was nearly systematically pre-grouted, grouting fans and grouts were designed individually for each place. After 1 km the fracture density decreased considerably and fractures became less open. As the tunnel has gone deeper the need for grouting has diminished. At the same time grouting has become more difficult due to the small fracture apertures and the high groundwater pressure. Besides the production grouting, Posiva Oy has developed acceptable grouts and grouting techniques for the deep rock and performed R&D projects have ended up to many recommendations e.g. the use of low pH grouts, analytical approach for grouting design, use of time and grout flow rate as stop criteria and the use of typical designs. The materials and design methods have been used and tested in ONKALO and results have been promising.
Grouting Experiences in Underground Research Facility Onkalo, Eurajoki, Finland
A Finnish company, Posiva Oy, is responsible for the research and management of the spent nuclear fuel from the Finnish nuclear power plants. Posiva Oy is constructing an underground research facility ONKALO, which is planned to be a part of the deep repository for high level nuclear waste. ONKALO has reached the depth of about -440 m. The construction started 2003 and the repository will be in use 2020. ONKALO is located in crystalline bedrock of which the fracturing properties, groundwater pressure and groundwater chemistry vary a lot with place and depth. The target for groundwater inflow is < 80 l/min in total for ONKALO (absolute acceptable maximum is 140 l/min). There are also local targets for major water conductive fracture zones. At the same time there are limitations for acceptable materials. The grouting materials have been studied and developed within several international R&D projects. During the tunnel driving, probe holes have been systematically bored and investigated by traditional water loss measurement and by Posiva flow log -device. Besides these, core drilled pilot holes have been drilled in places as the access tunnel has proceeded. In these holes detailed investigations have been done. These holes have produced much valuable data for grouting design. The grouting result has been controlled by measuring the groundwater inflow into the tunnel and by mapping of the leakage areas. The strict targets set for water inflow have been reached, except locally when the fracture zone HZ20 was intersected at the depth of ~300 m. When the access tunnel was about 4500 m long and three shafts were raise bored to the depth of -270 m, the total inflow was ~31 l/min. In the first 500-1000 m of the access tunnel, fracturing was quite dense and fracture apertures were reasonably large for the use of cement-based grouts. The first 1 km was nearly systematically pre-grouted, grouting fans and grouts were designed individually for each place. After 1 km the fracture density decreased considerably and fractures became less open. As the tunnel has gone deeper the need for grouting has diminished. At the same time grouting has become more difficult due to the small fracture apertures and the high groundwater pressure. Besides the production grouting, Posiva Oy has developed acceptable grouts and grouting techniques for the deep rock and performed R&D projects have ended up to many recommendations e.g. the use of low pH grouts, analytical approach for grouting design, use of time and grout flow rate as stop criteria and the use of typical designs. The materials and design methods have been used and tested in ONKALO and results have been promising.
Grouting Experiences in Underground Research Facility Onkalo, Eurajoki, Finland
Sievänen, Ursula (author) / Hollmén, Kalle (author) / Mustonen, Sanna (author) / Syrjänen, Pauli (author)
Proceedings of the Fourth International Conference on Grouting and Deep Mixing ; 2012 ; New Orleans, Louisiana, United States
Grouting and Deep Mixing 2012 ; 925-936
2012-08-17
Conference paper
Electronic Resource
English
Grouting Experiences in an Underground Research Facility: Onkalo, Eurajoki, Finland
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