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Deterioration of exposed buffer block: desiccation shrinkage and cracking

  • Yu Tan
  • Huyuan ZhangEmail author
  • Dongjin He
  • Guochao Zhang
Original Paper
  • 72 Downloads

Abstract

In high-level radioactive waste (HLW) repositories, buffer blocks are used for constructing engineering barrier to intercept radionuclides. Deterioration of exposed buffer blocks during their manufacture, storage, and transport may enlarge the hydraulic conductivity of an engineering barrier, reducing the barrier’s efficacy. It is not easy to monitor the shrinkage displacement by traditional tools because the shrinkage is less than 1 mm per day, while the monitoring length of the block is as large as 350 mm. Additionally, the cracks are often too narrow to allow for an accurate measurement of their depths. For this study, we used Gaomiaozi (GMZ) bentonite and quartz sand at a 7:3 mass ratio to compact fan-shape buffer blocks, and then exposed those blocks in an indoor environmental condition, which allowed desiccation of the blocks to occur. We monitored the overall and surface shrinkage of the blocks employing fixed dial indicators (FDIs) and digital image correlation (DIC), respectively. We excavated subsamples containing cracks from a desiccated block at various depths and estimated the depth of the cracks using Brazilian split tests. We also investigated the microstructure evolution of the blocks with mercury intrusion porosimetry (MIP) after exposure. Hierarchical evaporation of the block’s moisture was observed because the evaporating surface migrated inward rapidly, which led to the absence of initial evaporation stage. The shrinkage displacements of each measuring line were similar, while the longer measuring lines presented less shrinkage strain, indicating the uneven shrinkage. Moreover, the surface shrinkage of the blocks was greater than the overall shrinkage, revealing the interior of the blocks to be resistant to change during desiccation. Besides, the blocks’ inner pores showed less change, while the inter-aggregate pores on the block surface shrank visibly after exposure. The depth of the desiccated cracks was less than 26 mm, as estimated by the distribution of tensile strength. Because we found the varied deterioration levels between the block’s surface and interior, we determined that its structural integrity and efficacy were not as compromised as its surface seemed to indicate.

Keywords

Bentonite-sand mixture Buffer block Exposed deterioration Digital image correlation Hierarchical shrinkage Crack depth 

Notes

Acknowledgements

This work was supported by the National Nature Science Foundation of China (41672261) and Fundamental Research Funds for the Central Universities (lzujbky-2016-k15; lzujbky-2017-ct02); we are grateful for their financial support. And we gratefully acknowledge Mr. T.M. Luis for his language assistance.

Compliance with ethical standards

Conflict of interest

We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.

References

  1. Albrecht BA, Benson CH (2001) Effect of desiccation on compacted natural clays. J Geotech Geoenviron 127(1):67–75.  https://doi.org/10.1061/(ASCE)1090-0241(2001)127:1(67) Google Scholar
  2. An N, Tang CS, Xu SK, Gong XP, Shi B, Inyang HI (2018) Effects of soil characteristics on moisture evaporation. Eng Geol 239:126–135.  https://doi.org/10.1016/j.enggeo.2018.03.028 Google Scholar
  3. ASTM D4404-18 (2018) Standard test method for determination of pore volume and pore volume distribution of soil and rock by mercury intrusion porosimetry. ASTM International: West Conshohocken, PA.  https://doi.org/10.1520/D4404-18
  4. Birle E, Heyer D, Vogt N (2008) Influence of the initial water content and dry density on the soil–water retention curve and the shrinkage behavior of a compacted clay. Acta Geotech 3(3):191–200.  https://doi.org/10.1007/s11440-008-0059-y Google Scholar
  5. Chen L, Liu YM, Wang J, Cao SF, Xie JL, Ma LK, Zhao XG, Li YW, Liu J (2014) Investigation of the thermal-hydro-mechanical (THM) behavior of GMZ bentonite in the China-mock-up test. Eng Geol 172:57–68.  https://doi.org/10.1016/j.enggeo.2014.01.008 Google Scholar
  6. Chen YG, Sun Z, Ye WM, Cui YJ (2017) Adsorptive removal of Eu (III) from simulated groundwater by GMZ bentonite on the repository conditions. J Radioanal Nucl Chem 311(3):1839–1847.  https://doi.org/10.1007/s10967-017-5173-6 Google Scholar
  7. Chijimatsu M, Sugita Y, Amemiya K (1999) A Study on Manufacturing and Construction Method of Buffer. JNC TN8400 99–035, JNC: JapanGoogle Scholar
  8. Costa S, Kodikara J, Barbour SL, Fredlund DG (2018) Theoretical analysis of desiccation crack spacing of a thin, long soil layer. Acta Geotech 13(1):39–49.  https://doi.org/10.1007/s11440-017-0602-9 Google Scholar
  9. Delage P, Marcial D, Cui YJ, Ruiz X (2006) Ageing effects in a compacted bentonite: a microstructure approach. Géotechnique 56(5):291–304.  https://doi.org/10.1680/geot.2006.56.5.291 Google Scholar
  10. Dixon D, Sandén T, Jonsson E, Hansen J (2011) Backfilling of deposition tunnels: Use of bentonite pellets. P-10-15, SKB, SwedenGoogle Scholar
  11. Eriksson P (2014) Basic engineering of buffer production system. P-14-11, SKB, SwedenGoogle Scholar
  12. Eriksson P (2016) Investigation of alternatives to the buffer protection. P-16-07, SKB, SwedenGoogle Scholar
  13. Gapak Y, Das G, Yerramshetty U, Bharat TV (2017) Laboratory determination of volumetric shrinkage behavior of bentonites: a critical appraisal. Appl Clay Sci 135:554–566.  https://doi.org/10.1016/j.clay.2016.10.038 Google Scholar
  14. Gómez-Espina R, Villar MV (2015) Effects of heat and humidity gradients on MX-80 bentonite geochemistry and mineralogy. Appl Clay Sci 109:39–48.  https://doi.org/10.1016/j.clay.2015.03.012 Google Scholar
  15. Gui Y, Zhao GF (2015) Modelling of laboratory soil desiccation cracking using DLSM with a two-phase bond model. Comput Geotech 69:578–587.  https://doi.org/10.1016/j.compgeo.2015.07.001 Google Scholar
  16. Gui YL, Zhao GF, Khalili N (2012) Experimental investigation of desiccation of clayey soils. In 22th Australasian conference on the mechanics of structure and materials (ASMSM22) Sydney: AustraliaGoogle Scholar
  17. Gui YL, Zhao ZY, Kodikara J, Bui HH, Yang SQ (2016) Numerical modelling of laboratory soil desiccation cracking using UDEC with a mix-mode cohesive fracture model. Eng Geol 202:14–23.  https://doi.org/10.1016/j.enggeo.2015.12.028 Google Scholar
  18. Hallett PD, Newson TA (2005) Describing soil crack formation using elastic–plastic fracture mechanics. Eur J Soil Sci 56(1):31–38.  https://doi.org/10.1111/j.1365-2389.2004.00652.x Google Scholar
  19. Hillel D (1982) Introduction to soil physics. Academic press, New YorkGoogle Scholar
  20. IAEA (2013) Characterization of Swelling Clays as Components of the Engineered Barrier System for Geological Repositories. IAEA-TECDOC-1718, IAEA, AustriaGoogle Scholar
  21. Juvankoski M (2010) Description of basic Design for Buffer (working report). Technical Report. Eurajoki, Finland, pp 2009–2131Google Scholar
  22. Khan FS, Azam S (2017) Determination of the desiccation behavior of clay slurries. Int J Min Sci Technol 27(6):981–988.  https://doi.org/10.1016/j.ijmst.2017.06.010 Google Scholar
  23. Komine H (2008) Theoretical equations on hydraulic conductivities of bentonite-based buffer and backfill for underground disposal of radioactive wastes. J Geotech Geoenviron 134(4):497–508.  https://doi.org/10.1061/(ASCE)1090-0241(2008)134:4(497) Google Scholar
  24. Martin PL, Barcala JM (2005) Large scale buffer material test: mock-up experiment at CIEMAT. Eng Geol 81(3):298–316.  https://doi.org/10.1016/j.enggeo.2005.06.013 Google Scholar
  25. Nahlawi H, Kodikara JK (2006) Laboratory experiments on desiccation cracking of thin soil layers. Geotech Geol Eng 24(6):1641–1664.  https://doi.org/10.1007/s10706-005-4894-4 Google Scholar
  26. Nyblad B, Luterkort D, Lundqvist M (2014) Buffer protection for the installation phase: Design and testing. P-13-51, SKB, SwedenGoogle Scholar
  27. Pacovský J, Svoboda J, Zapletal L (2007) Saturation development in the bentonite barrier of the mock-up-CZ geotechnical experiment. Phys Chem Earth 32(8–14):767–779.  https://doi.org/10.1016/j.pce.2006.03.005 Google Scholar
  28. Peron H, Laloui L, Hueckel T, Hu LB (2009a) Desiccation cracking of soils. Eur J Environ Civ Eng 13(7–8):869–888.  https://doi.org/10.1080/19648189.2009.9693159 Google Scholar
  29. Peron H, Hueckel T, Laloui L, Hu L (2009b) Fundamentals of desiccation cracking of fine-grained soils: experimental characterisation and mechanisms identification. Can Geotech J 46(10):1177–1201.  https://doi.org/10.1139/T09-054 Google Scholar
  30. Peters WH, Ranson WF (1982) Digital imaging techniques in experimental stress analysis. Opt Eng 21(3):213427.  https://doi.org/10.1117/12.7972925 Google Scholar
  31. Prat PC, Ledesma A, Lakshmikantha MR (2006) Size effect in the cracking of drying soil. In Fracture of Nano and Engineering Materials and Structures (pp. 1373–1374). Springer, Dordrecht.  https://doi.org/10.1007/1-4020-4972-2_682
  32. Sima J, Jiang M, Zhou C (2014) Numerical simulation of desiccation cracking in a thin clay layer using 3D discrete element modeling. Comput Geotech 56:168–180.  https://doi.org/10.1016/j.compgeo.2013.12.003 Google Scholar
  33. SKB (2010) Design, production and initial state of the buffer. TR-10-15, SKB, SwedenGoogle Scholar
  34. Tang C, Shi B, Liu C, Zhao L, Wang B (2008) Influencing factors of geometrical structure of surface shrinkage cracks in clayey soils. Eng Geol 101(3–4):204–217.  https://doi.org/10.1016/j.enggeo.2008.05.005 Google Scholar
  35. Tang CS, Shi B, Cui YJ, Liu C, Gu K (2012) Desiccation cracking behavior of polypropylene fiber–reinforced clayey soil. Can Geotech J 49(9):1088–1101.  https://doi.org/10.1139/t2012-067 Google Scholar
  36. Villar MV, Iglesias RJ, Gutiérrez-Álvarez C, Carbonell B (2018) Hydraulic and mechanical properties of compacted bentonite after 18 years in barrier conditions. Appl Clay Sci 160:49–57.  https://doi.org/10.1016/j.clay.2017.12.045 Google Scholar
  37. Wan Y, Xue Q, Liu L (2014) Study on the permeability evolution law and the micro-mechanism of CCL in a landfill final cover under the dry-wet cycle. Bull Eng Geol Environ 73(4):1089–1103.  https://doi.org/10.1007/s10064-014-0604-x Google Scholar
  38. Wang J, Su R, Chen WM, Guo YH, Jin YX, Wen ZJ, Liu YM (2006) Deep geological disposal of high-level radioactive wastes in China. Chin J Rock Mech Eng 25(4):649–658Google Scholar
  39. Wang Q, Tang AM, Cui YJ, Delage P, Gatmiri B (2012) Experimental study on the swelling behaviour of bentonite/claystone mixture. Eng Geol 124:59–66.  https://doi.org/10.1016/j.enggeo.2011.10.003 Google Scholar
  40. Wang Q, Tang AM, Cui YJ, Delage P, Barnichon JD, Ye WM (2013) The effects of technological voids on the hydro-mechanical behaviour of compacted bentonite–sand mixture. Soils Found 53(2):232–245.  https://doi.org/10.1016/j.sandf.2013.02.004 Google Scholar
  41. Wang LL, Zhang GQ, Hallais S, Tanguy A, Yang DS (2017) Swelling of shales: a multiscale experimental investigation. Energy Fuel 31(10):10442–10451.  https://doi.org/10.1021/acs.energyfuels.7b01223 Google Scholar
  42. Wang LL, Tang CS, Shi B, Cui YJ, Zhang GQ, Hilary I (2018a) Nucleation and propagation mechanisms of soil desiccation cracks. Eng Geol 238:27–35.  https://doi.org/10.1016/j.enggeo.2018.03.004 Google Scholar
  43. Wang J, Chen L, Su R, Zhao XG (2018b) The Beishan underground research laboratory for geological disposal of high-level radioactive waste in China: planning, site selection, site characterization and in situ tests. J Rock Mech Geotech Eng 10(3):411–435.  https://doi.org/10.1016/j.jrmge.2018.03.002 Google Scholar
  44. Wimelius H, Pusch R (2008) Buffer protection in the installation phase. R-08-137, SKB, SwedenGoogle Scholar
  45. Xu L, Ye WM, Chen B, Chen YG, Cui YJ (2016) Experimental investigations on thermo-hydro-mechanical properties of compacted GMZ01 bentonite-sand mixture using as buffer materials. Eng Geol 213:46–54.  https://doi.org/10.1016/j.enggeo.2016.08.015 Google Scholar
  46. Yamaguchi I (1981) A laser-speckle strain gauge. Journal of Physics E: Scientific Instruments 14(11):1270–1273Google Scholar
  47. Zhang M, Zhang HY, Jia LY, Cui SL (2012) Salt content impact on the unsaturated property of bentonite–sand buffer backfilling materials. Nucl Eng Des 250:35–41.  https://doi.org/10.1016/j.nucengdes.2012.05.012 Google Scholar
  48. Zhang Y, Ye WM, Chen B, Chen YG, Ye B (2016) Desiccation of NaCl-contaminated soil of earthen heritages in the site of Yar City, Northwest China. Appl Clay Sci 124:1–10.  https://doi.org/10.1016/j.clay.2016.01.047 Google Scholar
  49. Zhao XG, Wang J, Chen F, Li PF, Ma KL, Xie JL, Liu YM (2016) Experimental investigations on the thermal conductivity characteristics of Beishan granitic rocks for China’s HLW disposal. Tectonophysics 683:124–137.  https://doi.org/10.1016/j.tecto.2016.06.021 Google Scholar
  50. Zhao NF, Ye WM, Chen YG, Chen B, Cui YJ (2017) Investigation on swelling-shrinkage behavior of unsaturated compacted GMZ bentonite on wetting-drying cycles. Bull Eng Geol Environ:1–11.  https://doi.org/10.1007/s10064-017-1095-3
  51. Zhou L, Zhang HY, Yan M, Chen H, Zhang M (2013) Laboratory determination of migration of Eu (III) in compacted bentonite–sand mixtures as buffer/backfill material for high-level waste disposal. Appl Radiat Isot 82:139–144.  https://doi.org/10.1016/j.apradiso.2013.07.004 Google Scholar
  52. Zhu LP, Zhang HY, Tan Y, Yuan W, Liu P (2018) The determination of the optimal bentonite-sand ration based on fuzzy integrated evaluation. Journal of Lanzhou University (Natural Sciences) 54(3):310–316 (In Chinese)Google Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Yu Tan
    • 1
  • Huyuan Zhang
    • 1
    • 2
    Email author
  • Dongjin He
    • 1
  • Guochao Zhang
    • 1
  1. 1.School of Civil Engineering and MechanicsLanzhou UniversityLanzhouChina
  2. 2.Key Laboratory of Mechanics on Disaster and Environment in Western ChinaLanzhou University, Ministry of EducationLanzhouChina

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