PROJECT RESULTS / Annual Technical Results
Year 3 : ESDRED TECHNICAL RESULTS to January 2007
Module 4 : Low pH Cement for Shotcrete and Sealing Plug Construction Technology
Summary :
During past year the short low-pH shotcrete plug constructed by the end of 2005 at Äspö URL was hydraulically loaded stepwise up to failure in the beginning of 2006. A data base was created. The plug was dismantled, carefully sampled and the site decommissioned. The results of the test provided valuable information about the mechanical behaviour of a confined granite-shotcrete interface, which was used to improve the plug design calculation procedure.
A new full-scale (4 m-long, 3.5 m in diameter) low-pH shotcrete plug test has been planned and will be constructed in the Grimsel Test Site (Switzerland) early 2007. The aim is to demonstrate the behaviour of a plug, under realistic conditions of an underground repository, that is loaded with the swelling pressure of a bentonite buffer that will be artificially hydrated. A preliminary shotcreting test has been carried out in December 2006 in a full-scale mock-up set constructed in the subcontractor's facilities in Sargans (Switzerland).
The selection of low-pH shotcrete for rock support was
reached on February 21st 2006 including the pilot tests at Swedish State
Power Board Research Facility at Älvkarleby, Sweden. SKB / POSIVA have
analyzed the results of the shotcrete tests for rock support completed at
Äspö HRL in April 2006. The shotcrete was tested with respect
to mechanical properties, bonding between rock and shotcrete and between
the different shotcrete layers. NAGRA has analyzed the results of the shotcrete
tests for rock support completed at the Hagerbach Test Gallery in Sargans
(Switzerland) in November 2006.
Work completed :
- Short low-pH plug test and dismantling
- Full-scale low-pH plug design
Layout of the full-scale low-pH shotcrete plug test at Grimsel URL
- Design and testing of low-pH shotcrete for rock support
Low-pH
shotcrete for rock support: field activities is Sweden (left) and Switzerland
(right)
Work Underway :
- Test site preparation and full-scale low-pH shotcrete plug test construction
- Start of full-scale low-pH shotcrete plug test operational phase (testing)
- Reporting of the results from the full-scale low-pH shotcrete plug test construction and the rock support field tests
Important Events Planned for 2007 :
By March 2007 the operational phase of the full-scale low-pH shotcrete plug test will be started. The operational phase comprises several steps for the artificial hydration of the bentonite buffer that will load the plug. Such test was fully instrumented to register the evolution of different parameters of the plug and the bentonite buffer: water and mechanical pressures, displacements, humidities, etc.