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Utilities
ABSTRACT There are methods and applications for assessing the stability of caverns during the construction period. However, little focus is paid to the maintenance for existing caverns. A maintenance method for existing caverns is focused in this paper and proposed. The continuous monitoring data on the deformation and/or the stress situation of the supports and the surrounding rock are utilized to elaborate a numerical model that fits the current mechanical condition of the cavern. Then using the numerical model, the future behavior of the cavern is simulated under the possible risks, involving the deterioration of the surrounding rock and/or PS anchors. The maintenance criteria are established for the future behavior of the existing cavern based on the results with the comparison to the critical state of the material forming the cavern and the surrounding rock. These processes are summarized as the maintenance flow-chart for the existing caverns.
- Energy > Renewable > Hydroelectric (0.41)
- Energy > Power Industry > Utilities (0.41)
Development of Grouting Technologies for HLW Disposal in Japan (3) – Development of a Hydro-geological Model using a Discrete Fracture Network –
Bruines, Patrick A. (Obayashi Corporation) | Tanaka, Tatsuya (Obayashi Corporation) | Hashimoto, Shuji (CFC Inc.) | Kuzuha, Yuji (Japan Atomic Energy Agency (JAEA)) | Ohnishi, Yuzo (Kyoto University)
ABSTRACT To better understand the grouting process and the effect of grouting on the performance of a nuclear waste repository, the Japanese Atomic Energy Agency has initiated a grouting test carried out in the fractured granite of the Grimsel Test Site in Switzerland. This paper describes the characterization of the rock mass carried out over a three year period, and how the data obtained has been used to make a discrete fracture network (DFN) model that attempts to account for as much known knowledge as possible (e.g. the location and orientation of fractures observed in the boreholes and the measured hydraulic transmissivity of 46 short intervals). Based on the DFN model developed, an equivalent continuous porous media (ECPM) model is generated for the purpose of numerical simulation of the grout injection process. The results of tracer testing have been used to optimize the specific storage and porosity distribution of the ECPM model.
Development of Grouting Technologies for HLW Disposal in Japan(1) Overall Program and Key Engineering Technologies
Fujita, Tomoo (Japan Atomic Energy Agency) | Kawaguchi, Masanao (Japan Atomic Energy Agency) | Walker, Colin S. (Japan Atomic Energy Agency) | Sasamoto, Hiroshi (Japan Atomic Energy Agency) | Yui, Mikazu (Japan Atomic Energy Agency) | Ohnishi, Yuzo (Kyoto University)
ABSTRACT The Japan Atomic Energy Agency (JAEA) started the JAEA Grout Project (JGP) in 2007, to investigate new grouting technologies and grout materials and to develop models for handling grout effects in performance assessment (PA), prediction of the long-term radionuclide migration and of host rock alteration. This paper presents an overview of the JGP and an example of how to apply key engineering technologies to the construction and operation of a purpose built underground facility (repository) for the geological disposal of high level nuclear waste (HLW). Further details of the outcome of the JGP can be found in papers (2–5) of the same series (Nakanishi et al., 2012, Bruineset al., 2012, Tanaka et al. 2012, and Koyama et al. 2012).
- Geology > Rock Type (0.47)
- Geology > Geological Subdiscipline > Geomechanics (0.31)
- Water & Waste Management (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Energy > Power Industry > Utilities > Nuclear (0.48)
ABSTRACT An in situ borehole heater test was carried out in an underground research tunnel, which is for the validation of high-level radioactive waste disposal system suggested in Korea. For the test at a shallow depth in granite, the thermal and mechanical properties of rock were measured at different conditions. During the test, the heater temperature was increased to 90°C to simulate the thermo-mechanical behavior of crystalline rock under normal underground repository conditions. For simulating an abnormal over heating condition, the heater temperature was increased to 115°C at the end of the test. The air, wall and rock temperatures were measured over a period of several years. The peak temperatures at the observation holes located at 0.3m and 0.6m from the heater hole were approximately 50°C and 37°C, respectively. From the temperature measurements, it was possible to observe thee influence of rock joints and the influence of heat convection through the tunnel wall.
- North America (0.29)
- Asia > South Korea (0.15)
- Geology > Rock Type > Igneous Rock (1.00)
- Geology > Geological Subdiscipline > Geomechanics (0.90)
- Well Drilling (1.00)
- Health, Safety, Environment & Sustainability > Environment > Waste management (0.90)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (0.69)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (0.68)
ABSTRACT The evolution of the long-term mechanical, hydraulic, and transport characteristics of rock fractures must be predicted in advance by considering the issue of the underground deposits of the energy by products of high-level radioactive waste. This paper presents slide-hold-slide direct shear experiments conducted for rock salt (halite) specimens with single fractures so as to investigate the effects of load holding on the mechanical properties of rock joints. From the experimental results, it is confirmed that the shear stress reduction can be observed during load holding. It is also confirmed that the shear strength recovery can be observed after load holding and it is found to increase with the increment of load holding period. This is because the dominant factor in the shear strength recovery during holding may be attributed to a purely mechanical process, like creep deformation at the contacting asperities.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Mineral > Halide > Halite (0.95)
Effect of Temperature and Confining Pressure on Permeability During Deformation and Failure of Shikotsu Welded Tuff
Badrula, Alam A.K.M. (Hokkaido University) | Niioka, Masaki (Hokkaido University) | Fujii, Yoshiaki (Hokkaido University) | Kodama, Jun-ichi (Hokkaido University) | Sugawara, Takayuki (Hokkaido University)
ABSTRACT Permeability variation during deformation and failure in triaxial test was considered for Shikotsu welded tuff. Pure water saturated cylindrical test specimens of 30 mm in diameter and length of 60 mm with constant flow rate method at 0.3 ml/min was introduced for compression, with strain rate of 10- s on the consolidated samples under 1 MPa, 5 MPa, 10 MPa and 15 MPa for 24 hours until the axial strain reached at 10% in 22°C and 80°C. Permeability at the end of 15 MPa consolidation was lower than those of under 1–10 MPa. In compression permeability basically decreased with slight disturbances around peak load points due to rapid volumetric change under 1 MPa the permeability was larger, compare to 5–15 MPa confining pressure at 22°C no apparent confining pressure dependency was observed at 80°C. The permeability was lower at 80°C than 22°C. However, more water flow is expected for the same pore pressure gradient at 80°C due to lower viscosity of water.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type (0.93)