Physicochemical controls on initiation and evolution of desiccation cracks in sand-bentonite mixtures: X-ray CT imaging and stochastic modeling

Thomas Gebrenegus, Teamrat A. Ghezzehei, Markus Tuller

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

The shrink-swell behavior of active clays in response to changes in physicochemical conditions creates great challenges for construction of geotechnical barriers for hazardous waste isolation, and is of significant importance for management of agricultural and natural resources. Initiation and evolution of desiccation cracks in active clays are strongly dependent on physicochemical initial and boundary conditions. To investigate effects of bentonite content (20, 40, 60%), pore fluid chemistry (0.05 and 0.5 M NaCl) and drying rates (40 and 60 °C) on cracking behavior, well-controlled dehydration experiments were conducted and X-ray Computed Tomography (CT) was applied to visualize and quantify geometrical features of evolving crack networks. A stochastic model based on the Fokker-Plank equation was adopted to describe the evolution of crack aperture distributions (CAD) and to assess the impact of physicochemical factors on cracking behavior. Analyses of crack porosity and crack specific surface area showed that both clay content and temperature had larger impact on cracking than pore fluid concentration. More cracks formed at high bentonite contents (40 and 60%) and at high drying rate (60 °C). The drift, diffusion and source terms derived from stochastic analysis indicated that evaporative demand had greater influence on the dynamics of the CAD than solution chemistry.

Original languageEnglish (US)
Pages (from-to)100-112
Number of pages13
JournalJournal of Contaminant Hydrology
Volume126
Issue number1-2
DOIs
StatePublished - Sep 25 2011

Keywords

  • Bentonite barriers
  • Desiccation cracks
  • Fokker-Plank equation
  • Physicochemical conditions
  • Stochastic modeling
  • X-ray computed tomography

ASJC Scopus subject areas

  • Environmental Chemistry
  • Water Science and Technology

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