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Abstract: Experiments of saturated water flow and heat transfer were conducted for a meter-scale model of regularly fractured granite. The fractured rock model (height 1502.5 mm, width 904 mm, and thickness 300 mm), embedded with two vertical and two horizontal fractures of pre-set apertures, was constructed using 18 pieces of intact granite. The granite was taken from a site currently being investigated for a high-level nuclear waste repository in China. The experiments involved different heat source temperatures and vertical water fluxes in the embedded fractures either open or filled with sand. A finite difference scheme and computer code for calculation of water flow and heat transfer in regularly fractured rocks was developed, verified against both the experimental data and calculations from the TOUGH2 code, and employed for parametric sensitivity analyses. The experiments revealed that, among other things, the temperature distribution was influenced by water flow in the fractures, especially the water flow in the vertical fracture adjacent to the heat source, and that the heat conduction between the neighboring rock blocks in the model with sand-filled fractures was enhanced by the sand, with larger range of influence of the heat source and longer time for approaching asymptotic steady-state than those of the model with open fractures. The temperatures from the experiments were in general slightly smaller than those from the numerical calculations, probably due to the fact that a certain amount of outward heat transfer at the model perimeter was unavoidable in the experiments. The parametric sensitivity analyses indicated that the temperature distribution was highly sensitive to water flow in the fractures, and the water temperature in the vertical fracture adjacent to the heat source was rather insensitive to water flow in other fractures.

[1]Alonso, E.E., Alcoverro, J., Coste, F., Malinsky, L., Merrien- Soukatchoff, V., Kadiri, I., Nowak, T., Shao, H., Nguyen, T.S., Selvadurai, A.P.S., et al., 2005. The FEBEX benchmark test: case definition and comparison of modelling approaches. International Journal of Rock Mechanics and Mining Sciences, 42(5-6):611-638.

[2]Čermak, V., Jetel, J., 1985. Heat flow and ground water movement in the Bohemian cretaceous basin (Czechoslovakia). Journal of Geodynamics, 4(1-4):285-303.

[3]Chan, T., Khair, K., Jing, L., Ahola, A., Noorishad, M., Vuillod, E., 1995. International comparison of coupled thermo-hydro-mechanical models of a multiple-fracture bench mark problem: DECOVALEX phase I, bench mark test 2. International Journal of Rock Mechanics and Mining Sciences, 32(5):435-452.

[4]Cheng, A.H.D., Ghassemi, A., Detournay, E., 2001. Integral equation solution of heat extraction from a fracture in hot dry rock. International Journal for Numerical and Analytical Methods in Geomechanics, 25(13):1327-1338.

[5]Chijimatsu, M., Fujita, T., Sugita, Y., Amemiya, K., Kobayashi, A., 2001. Field experiment, results and THM behaviour in the Kamaishi mine experiment. International Journal of Rock Mechanics and Mining Sciences, 38(1):67-68.

[6]Ghassemi, A., Tarasovs, S., Cheng, A.H.D., 2003. An integral equation solution for three-dimensional heat extraction from planar fracture in hot dry rock. International Journal for Numerical and Analytical Methods in Geomechanics, 27(12):989-1004.

[7]Gringarten, A.C., Witherspoon, P.A., Ohnishi, Y., 1975. Theory of heat extraction from fractured hot dry rock. Journal of Geophysical Research, 80(8):1120-1124.

[8]Ito, A., Yum, M., Sugita, Y., Kawakami, S., 2004. A Research Program for Numerical Experiments on the Coupled Thermo-Hydro-Mechanical and Chemical Processes in the Near-Field of a High-Level Radioactive Waste Repository. In: Stephansson, O. (Ed.), Coupled Thermo-Hydro- Mechanical-Chemical Processes in Geo-Systems: Fundamentals, Modelling, Experiments and Applications, 2:353- 358.

[9]Jing, L., Tsang, C.F., Stephansson, O., 1995. DECOVALEX— an international co-operative research project on mathematical models of coupled THM processes for safety analysis of radioactive waste repositories. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 32(5):389-398.

[10]Lenhart, T., Eckhardt, K., Fohrer, N., Frede, H.G., 2002. Comparison of two different approaches of sensitivity analysis. Physics and Chemistry of the Earth, Parts A/B/C, 27(9-10):645-654.

[11]Liu, Q., Zhang, C., Liu, X., 2006. Numerical modeling and simulation of coupled THM processes in Task-D of DECOVALEX IV. Chinese Journal of Rock and Mechanics and Engineering, 25(4):709-720 (in Chinese).

[12]Liu, X., Xiang, Y.Y., 2012. Numerical modeling of water flow and heat transfer in a meter-scale physical model of fractured rocks. Rock and Soil Mechanics, 33(1):287-294 (in Chinese).

[13]Millard, A., Stietel, A., Bougnoux, A., Vuillod, E., 1996. Generic Study of Coupled THM Processes of Nuclear Waste Repositories as Far-Field Initial Boundary Value Problems (BMT1). In: Stephansson, O., Jing, L., Tsang, C.F. (Eds.), Coupled Thermo-Hydro-Mechanical Processes of Fractured Media: Mathematical and Experimental Studies, 79:245-279.

[14]Rutqvist, J., Borgesson, L., Chijimatsu, M., Nguyen, S.T., Jing, L., Noorishad, J., 2001. Coupled thermo-hydro- mechanical analysis of a heater test in fractured rock and bentonite at Kamaishi Mine—comparison of field results to predictions of four finite element codes. International Journal of Rock Mechanics and Mining Sciences, 38(1):129-142.

[15]Rutqvist, J., Chijimatsu, M., Jing, L., Millard, A., Nguyen, T.S., Rejeb, A., 2005. Numerical study of the THM effects on the near-field safety of a hypothetical nuclear waste repository-BMT1 of the DECOVALEX III project. Part 3: Effect of THM coupling in sparsely fractured rocks. International Journal of Rock Mechanics and Mining Sciences, 42(5-6):745-755.

[16]Schulz, R., 1987. Analytical model calculations for heat exchange in a confined aquifer. Journal of Geophysics, 61:12-20.

[17]Tao, W., 2003. Numerical Heat Transfer (2nd Edition). Xi’An Jiaotong University Press, China (in Chinese).

[18]Tsang, C.F., Jing, L., Stephansson, O., Kautsky, F., 2005. The DECOVALEX III project: a summary of activities and lessons learned. International Journal of Rock Mechanics and Mining Sciences, 42(5-6):593-610.

[19]Tsang, C.F., Stephansson, O., Jing, L., Kautsky, F., 2009. DECOVALEX project: from 1992 to 2007. Environmental Geology, 57(6):1221-1237.

[20]Wilcock, P., 1996. Generic Study of Coupled T-H-M Processes in the Near Field (BMT3). In: Stephansson, O., Jing, L., Tsang, C.F. (Eds.), Coupled Thermo-Hydro- Mechanical Processes of Fractured Media: Mathematical and Experimental Studies, 79:311-340.

[21]Xiang, Y.Y., Guo, J.Q., 2011. A Laplace transform and Green function method for calculation of water flow and heat transfer in fractured rocks. Rock and Soil Mechanics, 32(2):333-340 (in Chinese).

[22]Xiang, Y.Y., Zhang, Y., 2012. Two-dimensional integral equation solution of advective-conductive heat transfer in sparsely fractured water-saturated rocks with heat source. International Journal of Geomechanics, 12(2):168-175.