Numerical simulation for influences of pressure solution on T-H-M coupling in aggregate rock

Abstract

The pressure solution model of granular aggregates was introduced into a FEM code which was developed for the analysis of thermo-hydro-mechanical (T-H-M) coupling in porous medium. Aimed at creating a hypothetical model of nuclear waste disposal in unsaturated quartz aggregate rock mass with laboratory scale, two 4-year computation cases were designed: 1) The porosity and permeability of rock mass are functions of the pressure solution; 2) The porosity and the permeability are constants. Calculation results show that the magnitude and distribution of stresses in the rock mass of these two calculation cases are roughly the same. And, the porosity and the permeability decrease to 43%–54% and 4.4%–9.1% of their original values after case 1 being accomplished; but the negative pore water pressures in cases 1 and 2 are respectively 1.0–1.25 and 1.0–1.1 times of their initial values under the action of nuclear waste. Case 1 exhibits the obvious effect of pressure solution.

Keywords

pressure solution / aggregate rock / thermo-hydro-mechanical (T-H-M) coupling / numerical simulation

References

[1] YasuharaH, ElsworthD, PolakA. A mechanistic model for compaction of granular aggregates moderated by pressure solution [J]. Journal of Geophysical Research, 2003, 108(B11): 2530

[2] TenthoreyE, CoxS F, ToddH F. Evolution of strength recovery and permeability during fluid-rock reaction in experimental fault zones [J]. Earth and Planetary Science Letters, 2003, 206(1/2): 161-172

[3] MooreD E, LocknerD A, ByerleeJ D. Reduction of permeability in granite at elevated temperatures [J]. Science, 1994, 265(5178): 1558-1561

[4] LinW, RobertsJ, GlassleyW, RuddleDFracture and matrix permeability at elevated temperatures [R], 1997, San Francisco, Workshop on Significant Issues and Available Data, Near-Field/Altered-Zone Coupled Effects Expert Elicitation Project

[5] Geophysical Research Letters, 2003, 30(20

[6] DurhamW B, BourcierW L, BurtonE A. Direct observation of reactive flow in a single fracture [J]. Water Resources Research, 2001, 371): 1-12

[7] YasuharaH, ElsworthD. Evolution of permeability in a natural fracture: Significant role of pressure solution [J]. Journal of Geophysical Research, 2004, 109(B3): B03204

[8] TaronJ, ElsworthD. Thermal-hydrologic-mechanical-chemical processes in the evolution of engineered geothermal reservoirs [J]. International Journal of Rock Mechanics and Mining Sciences, 2009, 46(5): 855-864

[9] TaronJ, ElsworthD. Coupled mechanical and chemical processes in engineered geothermal reservoirs with dynamic permeability [J]. International Journal of Rock Mechanics and Mining Sciences, 2010, 47(8): 1339-1348

[10] TaronJ, ElsworthD. Constraints on compaction rate and equilibrium in the pressure solution creep of quartz aggregates and fractures: Controls of aqueous concentration [J]. Journal of Geophysical Research, 2010, 115(B7): B07211

[11] ZhengB, ElsworthD. Evolution of permeability in heterogeneous granular aggregates during chemical compaction: Granular mechanics models [J]. Journal of Geophysical Research, 2012, 117(B3): B03206

[12] ZhengB, ElsworthD. Strength evolution in heterogeneous granular aggregates during chemo-mechanical compaction [J]. International Journal of Rock Mechanics and Mining Sciences, 2013, 60: 217-226

[13] LeeD S, ElsworthD, YasuharaH, WeaverJ D, RickmanR. Experiment and modeling to evaluate the effects of proppant-pack diagenesis on fracture treatments [J]. Journal of Petroleum Science and Engineering, 2006, 74(1/2): 67-76

[14] ZhangY-j, YangC-shuai. FEM analyses for influences of stress-chemical solution on THM coupling in dual-porosity rock mass [J]. Journal of Central South University, 2012, 19(4): 1138-1147

[15] ZhangY-j, ZhangW-qing. 2D FEM analysis for coupled thermo-hydro-mechanical-migratory processes in near field of hypothetical nuclear waste repository [J]. Journal of Central South University of Technology, 2010, 17(3): 612-620

[16] ZhangY-j, ZhangW-qing. 3D thermo-hydro-mechanical-migratory coupling model and FEM analyses for dual-porosity medium [J]. SCIENCE CHINA, Technological Sciences, 2010, 53(8): 2172-2182

[17] RutqvistJ, ChijimatsuM, JingL, MillardA, NguyenT S, RejebA, SuffjaY, TsangC F. A numerical study of THM effects on the near-field safety of a hypothetical nuclear waste repository-BMT1 of the DECOVALEX III project. Part 3: Effects of THM coupling in sparsely fractured rocks [J]. International Journal of Rock Mechanics and Mining Sciences, 2005, 42(5/6): 745-755

[18] ChijimatsuM, KurikamiH, ItoA, SugitaY. Implication of THM coupling on the near-field of a nuclear waste repository in a homogeneous rock mass [R]. DECOVALES III-Task 3-Bench Mark Test 1 (BMT1)-Subtask BMT1-B, 2002