Effectiveness of fracture sealing with bentonite grouting

Technical Report · Sat Jun 01 04:00:00 EDT 1991

OSTI ID:5720253

Ran, C; Daemen, J J.K. ^[1]

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1. Arizona Univ., Tucson, AZ (USA). Dept. of Mining and Geological Engineering

Bentonite is known to have an extremely low permeability and a self-healing ability. It has therefore been selected as a major sealing component in several repository concepts. Bentonite grouts have the following advantages, (1) small particle size, can be injected into small fractures or voids, (2) suitable water absorption properties, can produce gels at low concentrations, and (3) stable physical and chemical properties, may have considerable longevity. Bentonite fracture grouting tests are performed on a model made of circular acrylic plates with outer diameter of 30 cm and central injection hole of 2.5 cm diameter. Suspension with bentonite concentration of 15% to 31% have been injected into fractures with apertures of 9 to 90 microns under injection pressures less than 0.6 MPa. Grouting reduces the hydraulic conductivities of the fractures from the 10{sup {minus}1} to the 10{sup {minus}5} cm/s level. When the suspension is thin enough and the fracture is very small, channeling develops in the grouted fractures. Preliminary results indicate that the permeability of a grouted fracture does not increase with time in more than 125 days. The flow properties of bentonite suspensions, viscosity, shear stress, yield stress and gelation, are investigated. Water flow through ungrouted fractures and movement of water in bentonite grout are studies. The physical stability or bleeding capacity of bentonite suspensions is determined. 122 refs., 56 figs., 10 tabs.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (USA). Div. of Engineering; Arizona Univ., Tucson, AZ (USA). Dept. of Mining and Geological Engineering
• Sponsoring Organization: NRC; Nuclear Regulatory Commission, Washington, DC (USA)
• OSTI ID: 5720253
• Report Number(s): NUREG/CR-5686; ON: TI91014868
• Country of Publication: United States
• Language: English

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360603 -- Materials-- Properties
BENTONITE
CLAYS
CRYSTAL STRUCTURE
FAILURES
FRACTURES
GROUTING
HYDRAULIC CONDUCTIVITY
MECHANICAL PROPERTIES
MICROSTRUCTURE
PARTICLE SIZE
PERMEABILITY
SIZE
VISCOSITY