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Tanaka, Tatsuya*; Uyama, Masao*; Ishida, Tomoko*; Nakanishi, Tatsuro; Onishi, Yuzo*
Proceedings of 7th Asian Rock Mechanics Symposium (ARMS-7) (USB Flash Drive), p.702 - 711, 2012/10
This paper describes the planning, material selection, execution and interpretation of the grout injection test carried out at the end of 2011 at the Grimsel Test Site (GTS) in Switzerland as part of grouting technology project of the Japan Atomic Energy Agency (JAEA). Based on the findings of the rockmass characterization part of the GTS grouting study (Nakanishi et al, 2012, Bruines et al., 2012), it was decided to perform the grout injection test in a 5 m interval with the highest expected hydraulic conductivity. During the grouting test the viscosity of the grout was continuously measured. Both the injected volume and pressure in the injection section were recorded. In the observation sections the pressure over time as well as the electric conductivity, which can be used to measure the arrival of the higher salinity silica grout, was recorded. As the grout reached the observation sections before the grout hardened the grout injection test was a success. The gathered data of the grouting test presents an important data set for further modeling efforts of the grouting process.
Bruines, P.*; Tanaka, Tatsuya*; Hashimoto, Shuji*; Kuzuha, Yuji; Onishi, Yuzo*
Proceedings of 7th Asian Rock Mechanics Symposium (ARMS-7) (USB Flash Drive), p.692 - 701, 2012/10
This paper describes the characterization of the rock mass and how data obtained has been used to make a discrete fracture network (DFN) model and to calculate an up-scaled equivalent continuous porous media model for the purpose of numerical simulation of the grout injection process. DFN models have been constructed using mainly the BTV and hydraulic test data from the boreholes drilled in this project. The generated DFN model and the up-scaled model was able to reproduce the measured fracture characteristics as well as the hydraulic behavior observed in the field and has proven to be suitable for modeling grouting behavior. DFN model has been gradually refined step by step with the site characterization stages: the preparative stage in 2009, pre-investigation stage in 2010 and grouting test stage in 2011. Each version of the DFN model shows the understanding of the geological environment and identifies issues to be resolved in the next stage. The DFN models proved to be an essential tool for the site characterization program planning process, such as identifying the best layout of subsequent boreholes and placement of test intervals.
Koyama, Tomofumi*; Katayama, Tatsuo*; Tanaka, Tatsuya*; Kuzuha, Yuji; Onishi, Yuzo*
Proceedings of 7th Asian Rock Mechanics Symposium (ARMS-7) (USB Flash Drive), p.712 - 720, 2012/10
Grouting is commonly used to decrease the hydraulic conductivity of the fractured rock masses and control the groundwater inflow. Since underground facilities were constructed in various geological conditions, different types of grout material and mixing/injection methods were developed for effective and economical grout injection. It is also important to evaluate the grout arrival distance and the range of altered hydraulic conductivity field after grout injection. However, the mechanism of grout injection process has not been clarified sufficiently yet due to complicated chemical and physical processes of grout. In this study, to simulate the grout injection process, the three-dimensional numerical model based on equivalent continuum approach was developed and applied to the in-situ grout injection tests at Grimsel test site, Switzerland. In the simulations, the injection pressure and/or injection rate was given as a boundary condition and total amount of injected grout (silica sol) was calculated. The simulation results were also compared with the ones obtained from in-situ measurements/monitoring and show qualitatively good agreement.
Nakanishi, Tatsuro; Tsuda, Hidenori; Abumi, Kensho*; Uyama, Masao*; Onishi, Yuzo*
Proceedings of 7th Asian Rock Mechanics Symposium (ARMS-7) (USB Flash Drive), p.682 - 691, 2012/10
JAEA has been developing grouting materials and technologies with the consideration of long term chemical interaction between the grout material and the rock mass as a natural barrier. This paper describes the in-situ grout injection test program carried out in the fractured granite of the Grimsel Test Site (GTS) in Switzerland, which has been set up to increase knowledge and understanding of the design of grouting in order to reduce the grout penetration area into the rock mass and of the results of the site investigation. The grout injection test project at the GTS has been carried out in several stages. The site investigation results of all six boreholes were then used to determine the best location for the final grout injection test. The staged approach proved to be a good way not only to determine the best location for the grout injection test, but also to focus on the best approach in the next stages by identifying and mitigating possible problems before they occurred.
Fujita, Tomoo; Kawaguchi, Masanao; Walker, C.; Sasamoto, Hiroshi; Yui, Mikazu; Onishi, Yuzo*
Proceedings of 7th Asian Rock Mechanics Symposium (ARMS-7) (USB Flash Drive), p.675 - 681, 2012/10
The Japan Atomic Energy Agency started new grout project for geological disposal of high-level radioactive waste in 2007. This study presented the overall JAEA grout project program and an example of how to apply key engineering technologies to the construction and operation of an underground facility for the geological disposal of HLW.