Rock Suitability Classification for POPLU

Transcription

1 The research leading to these results has received funding from the European Union's European Atomic Energy Community's (Euratom) Seventh Framework Programme FP7/ , 2013, under Grant Agreement No for the DOPAS project Rock Suitability Classification for POPLU DOPAS Excursion to Olkiluoto DOPAS Excursion to Olkiluoto, May 27th 2016

2 Contents 1. Posiva s Rock Suitability Classification (RSC) system 2. The demonstration facilities in ONKALO 3. Selection of the location for the POPLU plug Kosunen Paula (Posiva) Julkinen 2

3 1. Rock Suitability Classification (RSC) The RSC-system has been developed by Posiva to evaluate natural properties of the repository host rock for the purpose of locating suitable rock volumes for the various parts of the repository. The implementation of the RSC-system is carried out in stepwise manner and can be divided into four stages, which coincide with the stages of repository design and construction, proceeding from the design of the whole repository to the more detailed design and construction of panels, tunnels and, finally, deposition holes. POSIVA Repository layout-design Detailed positioning of the central tunnels Construction and acceptance of the deposition tunnels Detailed positioning of the plug and the deposition holes Construction and acceptance of the central tunnels Detailed positioning of the deposition tunnels Construction and acceptance of the plug slot and the deposition holes Julkinen

4 RSC-criteria The classification of host rock volumes is based on rock suitability criteria, which have been defined for the natural properties of the rock hosting the different parts of the repository. Thus, a volume of rock can be classified as suitable or unsuitable for hosting a deposition tunnel or a deposition hole, for example, based on its fulfilment of the criteria. The criteria are based on requirements stemming from aspects of long-term safety, related to the functioning of the bedrock as a natural barrier as well as to ensuring proper conditions for the functioning of the EBS-system. Thus, the criteria mostly deal with Chemical composition of the groundwater Groundwater flow Mechanical stability of the host rock The criteria need to be practical, verifiable by (relatively) standard investigation methods during the construction procedure of the repository. Rock suitability criteria for the plug location Three requirements have been defined for the rock hosting a plug slot: The plug location shall not be intersected by the respect volumes of hydrogeological zones. The plug location shall not be intersected by the respect volumes of brittle deformation zones. Hydraulically conductive fractures shall not intersect the entire length of the plug. These are still preliminary, and will be updated and complemented based on the experiences gained from POPLU and other ongoing tests Kosunen Paula Julkinen 4

5 DT2 2. The demonstration facilities in ONKALO DT1 DT3 DT4 DT1-4 experimental deposition holes constructed DT2-6 experimental deposition holes constructed DT3 - for the monitoring of the POPLU test plug DT4 - the POPLU test tunnel Kosunen Paula 5 Julkinen

6 Investigations in the demo area Commenced in 2010 Drillhole investigations 9 pilot holes and 2 characterisation holes geological, geophysical and hydrogeological investigations single and between hole measurements Tunnel investigations geological mapping inflow measurements ground-penetrating radar Tunnel seismic investigations Mise-a-la-masse measurements Julkinen

7 Detailed-scale modelling of the demo area Kosunen Paula Julkinen 7

8 Summary of the RSC and the related work in the demo area Posiva : RSC Kosunen Paula Julkinen 8

9 3. Rock suitability classification for the POPLU slot the starting situation The area immediately northeast of the existing demonstration tunnels 1 and 2 was considered a possible location for the POPLU demonstration on the basis of investigations and detailed-scale modelling of bedrock structures carried out earlier, during the construction of the two Demonstration tunnels 1 and 2. Detailed-scale model of the demonstration area, version 7; BFZ = brittle deformation zone, LF = large fracture Kosunen Paula Julkinen 9

10 Rock suitability classification for the POPLU slot Pilot hole investigations To further verify the suitability of the possible location, a pilot hole was drilled within the profile of each planned tunnel at the end of November 2012, and Posiva's standard set of drillhole investigations was carried out in the holes. A total of 75 natural fractures were observed and described from the pilot hole ONK-PH26 (DT3) and 21 from the pilot hole ONK-PH27 (DT4). A brittle deformation zone intersection was recorded from the pilot hole ONK- PH26 at the depth of metres; no zone intersections were observed in the pilot hole ONK-PH27. In the pilot hole ONK-PH26, the fracture flow directions measured using Posiva s PFL DIFF probe were negative, out of the hole into the bedrock, indicating a possible connection between the conductive fractures and open tunnel space. Typically, the flow directions in ONKALO are positive, out of the bedrock into the hole. The total measured outflow from ONK-PH26 was 10.3 ml/min; no flowing fractures were found in the pilot hole ONK-PH Kosunen Paula Julkinen 10

11 Rock suitability classification for the POPLU slot Detailed-scale model The brittle deformation zone intersection observed in the pilot hole ONK-PH26 could be correlated to a known brittle fault zone, OL-BFZ297. The zone is hydraulically conductive and explains the outflow measured in the pilot hole ONK-PH26. The geological model of the Olkiluoto site v. 2.0 (Posiva Working Report ) suggested the brittle fault zone OL-BFZ136 to intersect the planned Demonstration tunnel 4 at tunnel chainage m. However, no indications of the expected intersection were observed in the plot hole ONK-PH Kosunen Paula Julkinen DSM 11 v8

12 Rock suitability classification for the POPLU slot 1 st Suitability classification The first suitability classification was carried out in February Chainage m of the demonstration tunnel 3 was classified unsuitable for a plug, due to the water conductive brittle fault zone OL-BFZ297. If the brittle deformation zone OL-BFZ136 would, contrary to the pilot hole data, intersect the planned demonstration tunnel 4, the chainage m would be rendered unsuitable (unlikely). It was suggested, that chainage m in DT4 would preliminarily be chosen for the location of the POPLU plug, as the tunnel section Julkinenin question would likely be the best in rock quality Kosunen Paula 12

13 Rock suitability classification for the POPLU slot Tunnel investigations and detailed-scale modelling The excavation of Demonstration tunnel 4 commenced in September, No intersections of brittle deformation zones or hydrogeological zones were observed in Demonstration tunnel 4 tunnel during the geological mapping. Five significant fractures (with relatively long tunnel-surface traces) were observed in the chainage metres. None of the fractures crosscut the entire perimeter of the tunnel, and all of them were observed to be dry. No update of the detailed-scale model was needed based on the tunnel data from DT Kosunen Paula Julkinen 13

14 Rock suitability classification for the POPLU slot 2 nd Suitability classification The second suitability classification was carried out in October Based on the observations from the excavated tunnel, no hydrogeological or brittle deformation zones were present in the assessed tunnel section or the suggested plug location. Also, no fractures were present - hydraulically conductive or not - that would intersect the entire length of the plug. It was concluded that the criteria set for the plug location were fulfilled in the demonstration ti tunnel 4 in general and that t the suggested chainage m was suitable for the plug location Kosunen Paula Julkinen 14

15 Rock suitability classification for the POPLU slot Verification of suitability The construction of the slot was completed in January Geological mapping of the slot was carried out, and no features contradicting the results from the earlier suitability classifications were observed. It was noted that the constructed slot fulfilled the criteria set for a plug location Kosunen Paula Julkinen 15

16 KIITOS! THANK YOU! Kosunen Paula (Posiva) Julkinen 16