Temperature effect on the thermal and hydraulic conductivity of Korean bentonite buffer material

Nanoscale Prediction of the Thermal, Mechanical, and Transport Properties of Hydrated Clay on 106- and 1015-Fold Larger Length and Time Scales

“…For example, suction is slightly higher for unconfined samples that can swell freely than for those kept at a constant volume, 76 and bentonite with a large fraction of Ca exchangeable cations generally has a smaller suction than bentonite with predominantly Na ions. 58,77 Results obtained in this study show that suction can be slightly negative at low dry densities (less than 1000 kg m −3 ), in agreement with the known cohesive nature of clayey media 79 and with previous MD simulation results. 42,80,81 Possible origins of these negative suctions include configurational entropy effects and specific coulomb interactions in the compressed electrical double layer (EDL) between charged clay surfaces.…”

“…Experimental results obtained for bentonites that contain significant levels of divalent exchangeable cations (e.g., Ca 2+ and Mg 2+ ) are not presented in Figure 8, as these ions inhibit clay swelling and hence promote the persistence of clay aggregates and larger pores. 58,77 Depending on divalent cation abundance, hydraulic conductivities measured for bentonite with predominantly divalent exchangeable cations are 0.5 to 2 orders of magnitude larger than for Na-bentonite, as demonstrated in Figure A12 in the Supporting Information.…”

“…12,66,69 We also note that thermal strain is effective-stress dependent, and in particular, the thermal volumetric strain under high confining stress may occur as contractive rather than expansive because of the mechanical weakening of contacts. 13 Finally, we note that our simulations evaluate the thermal strain in undrained conditions and that additional processes related to osmotic 15,22,54,56,58,59,63,64 Experiments were performed using Kyeongju bentonite, 15 GMZ07 bentonite, 54 Kunigel V1 bentonite, 22 Gyeongju bentonite, 58 and MX-80 bentonite. 56,59,63,65 Figure 4.…”

“…Experimental studies on the hydraulic conductivity of bentonite have been extensively performed in the literature, but predominantly at high dry densities (ρ d > 1300 kg•m −3 ). 58,74,78,100,110 85,101−105 Results are normalized to the values in bulk liquid water, which eliminates most of the temperature dependence. Simulation predictions are reported in directions parallel or normal to the preferred orientation of the clay particles (squares and rhombi) and as a geometric average of diffusion in all directions (upward facing triangles).…”

The Effect of Porosity Change in Bentonite Caused by Decay Heat on Radionuclide Transport through Buffer Material

“…In the past decades, numerous research projects and studies have been conducted worldwide to understand the complex behavior of bentonite as a buffer material more widely and deeply, in geological radioactive waste disposal. A wide range of aspects related to the thermal-hydraulic-mechanical-chemical processes of bentonite have been studied, including high temperature influences on bentonite performance [9][10][11][12], groundwater/gas flow characteristics within bentonite [13][14][15][16][17], swelling pressure and mechanical properties [18][19][20][21][22][23][24][25], and the mineral chemical evolution of bentonite [26][27][28]. Moreover, experimental analysis and numerical simulation have been employed to study the performance evaluation of bentonite in the thermal-hydraulic-mechanical-chemical coupling process under environmental evolution conditions [29][30][31].…”