Modeling Coupled Evaporation and Seepage in Ventilated Cavities (original) (raw)

2004, Vadose Zone Journal

Abstract

conditions that trigger seepage into various idealized cavity geometries excavated in homogeneous forma-Cavities excavated in unsaturated geological formations are importions. Detailed numerical models have been used to tant to activities such as nuclear waste disposal and mining. Such study unsaturated flow in heterogeneous fractured mecavities provide a unique setting for simultaneous occurrence of seepdia and seepage into cavities of various geometries unage and evaporation. Previously, inverse numerical modeling of field der transient conditions (e.g., Birkholzer et al., 1999; liquid-release tests and associated seepage into cavities were used to provide seepage-related large-scale formation properties, ignoring the Finsterle, 2000; Finsterle and Trautz, 2001; Li and Tsang, impact of evaporation. The applicability of such models was limited 2003). Site-specific seepage models for the proposed to the narrow range of ventilation conditions under which the models nuclear waste repository at YM were developed by caliwere calibrated. The objective of this study was to alleviate this limitabrating the effective seepage-related parameters against tion by incorporating evaporation into the seepage models. We modfield seepage test data (Finsterle et al., 2003). eled evaporation as an isothermal vapor diffusion process. The semi-Most of the previous numerical models assumed that physical model accounts for the relative humidity (RH), temperature, liquid water leaking into a cavity drips (seeps) immediand ventilation conditions of the cavities. The evaporation boundary ately from the place of entry. The potential for evaporalayer thickness (BLT) over which diffusion occurs was estimated by tion to compete with seepage has been generally igcalibration against free-water evaporation data collected inside the nored, and its effect was lumped with the effective flow experimental cavities. The estimated values of BLT were 5 to 7 mm parameters of the unsaturated medium (Finsterle et al., for the open underground drifts and 20 mm for niches closed off by 2003). In calibration of the analytical model of Philip bulkheads. Compared with previous models that neglected the effect et al. (1989b) against field seepage data, Trautz and of evaporation, this new approach showed significant improvement Wang (2002) accounted for the effect of evaporation by in capturing seepage fluctuations into open cavities of low RH. At adjusting the field seepage data for evaporation. Behigh relative-humidity values (ΟΎ85%), the effect of evaporation on cause the data were obtained from tests conducted in seepage was very small.

Loading...

Loading Preview

Sorry, preview is currently unavailable. You can download the paper by clicking the button above.

References (19)

  1. Res. 25:1447-1448.
  2. Bear, J. 1972. Dynamics of fluids in porous media. Elsevier, New York. Philip, J.R., J.H. Knight, and R.T. Waechter. 1989a. The seepage Birkholzer, J., G.M. Li, C.F. Tsang, and Y. Tsang. 1999. Modeling exclusion problem for parabolic and paraboloidal cavities. Water studies and analysis of seepage into drifts at Yucca Mountain. J. Resour. Res. 25:605-618.
  3. Contam. Hydrol. 38:349-384.
  4. Philip, J.R., J.H. Knight, and R.T. Waechter. 1989b. Unsaturated Bodvarsson, G.S., W. Boyle, R. Patterson, and D. Williams. 1999. seepage and subterranean holes-Conspectus, and exclusion prob- Overview of scientific investigations at Yucca Mountain-The po- lem for circular cylindrical cavities. Water Resour. Res. 25:16-28. tential repository for high-level nuclear waste. J. Contam. Hy- Pruess, K., C. Oldenburg, and G. Moridis. 1999. TOUGH2 user's drol. 38:3-24. guide. Version 2.0. LBNL-43134. Lawrence Berkeley Natl. Lab., Deutsch, C.V., and A.G. Journel. 1992. GSLIB: Geostatistical soft- Berkeley, CA.
  5. ware library and user's guide. Oxford University Press, New York. Rohsenow, W.M., and H. Choi. 1961. Heat, mass and momentum Finsterle, S. 1999. iTOUGH2 user 's guide. Rep. LBNL-40040. Law- transfer. Prentice Hall, Englewood Cliffs, NJ.
  6. Trautz, R.C., and J.S.Y. Wang. 2001. Evaluation of seepage into an
  7. Finsterle, S. 2000. Using the continuum approach to model unsatu- underground opening using small-scale field experiments, Yucca rated flow in fractured rock. Water Resour. Res. 36:2055-2066. Mountain, Nevada. Min. Eng. 53:41-44.
  8. Finsterle, S., C.F. Ahlers, R.C. Trautz, and P.J. Cook. 2003. Inverse Trautz, R.C., and J.S.Y. Wang. 2002. Seepage into an underground and predictive modeling of seepage into underground openings. J. opening constructed in unsaturated fractured rock under evapora- Contam. Hydrol. 62-63:89-109. tive conditions. Water Resour. Res. 38:(10)1188. doi:10.1029/2001
  9. Fujimaki, H., and M. Inoue. 2003. A transient evaporation method WR000690. for determining soil hydraulic properties at low pressure. Available van Genuchten, M.Th. 1980. A closed-form equation for predicting at www.vadosezonejournal.org. Vadose Zone J. 2:400-408. the hydraulic conductivity of unsaturated soils. Soil Sci. Soc. Am.
  10. Finsterle, S., and R.C. Trautz. 2001. Numerical modeling of seepage J. 44:892-898.
  11. into underground openings. Min. Eng. 53:52-56.
  12. Vargaftik, N.B. 1975. Tables on the thermophysical properties of
  13. Ho, C.K. 1997. Evaporation of pendant water droplets in fractures. liquids and gases. 2nd ed. John Wiley & Sons, New York.
  14. Water Resour. Res. 33:2665-2671.
  15. Wang, J.S.Y., R.C. Trautz, P.J. Cook, S. Finsterle, A.L. James, and Knight, J.H., J.R. Philip, and R.T. Waechter. 1989. The seepage exclu- J. Birkholzer. 1999. Field tests and model analyses of seepage into sion problem for spherical cavities. Water Resour. Res. 25:29-37. drift. J. Contam. Hydrol. 38:323-347.
  16. LeCain, G.D. 1995. Pneumatic testing in 45-degree-inclined boreholes Zhang, J.T., and B.X. Wang. 2002. Effect of capillarity at liquid-vapor in ash-flow tuff near Superior, Arizona. USGS Water Resour. interface on phase change without surfactant. Int. J. Heat Mass Invest. Rep. 95-4073. USGS, Denver, CO. Transfer 45:2689-2694.
  17. Li, G.M., and C.-F. Tsang. 2003. Seepage into drifts with mechanical Zhang, J.T., B.X. Wang, and X.F. Peng. 2001. Thermodynamic aspect degradation. J. Contam. Hydrol. 62:157-172. of the shift of concave liquid-vapor interfacial phase equilibrium
  18. Murray, F.W. 1966. On the computation of saturation vapor pressure. temperature and its effect on bubble formation. Int. J. Heat Mass Transfer 44:1681-1686.
  19. J. Appl. Meteorol. 6:204.