Bond strength of cementitious borehole plugs in welded tuff

Technical Report · Fri Feb 01 00:00:00 EST 1991

DOI:https://doi.org/10.2172/138038· OSTI ID:138038

Akgun, H; Daemen, J J.K. ^[1]

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

Axial loads on plugs or seals in an underground repository due to gas, water pressures and temperature changes induced subsequent to waste and plug emplacement lead to shear stresses at the plug/rock contact. Therefore, the bond between the plug and rock is a critical element for the design and effectiveness of plugs in boreholes, shafts or tunnels. This study includes a systematic investigation of the bond strength of cementitious borehole plugs in welded tuff. Analytical and numerical analysis of borehole plug-rock stress transfer mechanics is performed. The interface strength and deformation are studied as a function of Young`s modulus ratio of plug and rock, plug length and rock cylinder outside-to-inside radius ratio. The tensile stresses in and near an axially loaded plug are analyzed. The frictional interface strength of an axially loaded borehole plug, the effect of axial stress and lateral external stress, and thermal effects are also analyzed. Implications for plug design are discussed. The main conclusion is a strong recommendation to design friction plugs in shafts, drifts, tunnels or boreholes with a minimum length to diameter ratio of four. Such a geometrical design will reduce tensile stresses in the plug and in the host rock to a level which should minimize the risk of long-term deterioration caused by excessive tensile stresses. Push-out tests have been used to determine the bond strength by applying an axial load to cement plugs emplaced in boreholes in welded tuff cylinders. A total of 130 push-out tests have been performed as a function of borehole size, plug length, temperature, and degree of saturation of the host tuff. The use of four different borehole radii enables evaluation of size effects. 119 refs., 42 figs., 20 tabs.

• Research Organization: US Nuclear Regulatory Commission (NRC), Washington, DC (United States). Div. of Engineering; Arizona Univ., Tucson, AZ (United States). Dept. of Mining and Geological Engineering
• Sponsoring Organization: Nuclear Regulatory Commission, Washington, DC (USA)
• OSTI ID: 138038
• Report Number(s): NUREG/CR-4295; ON: TI91009035; TRN: 91:009460
• Resource Relation: Other Information: PBD: Feb 1991
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
SEALING MATERIALS
MECHANICAL PROPERTIES
TUFF
PLUGGING
BOREHOLES
RADIOACTIVE WASTE FACILITIES
SEALS
DESIGN
CEMENTS
MECHANICAL TESTS
MATHEMATICAL MODELS
STRESS ANALYSIS
UNDERGROUND STORAGE
UNDERGROUND DISPOSAL
GASES
WATER
TEMPERATURE GRADIENTS
STRESSES
SHEAR
CRACKS
PERMEABILITY
TENSILE PROPERTIES
INTERFACES
DEFORMATION
YOUNG MODULUS
DIMENSIONS
FRICTION FACTOR
TUNNELS
MINE SHAFTS
RESERVOIR ROCK
TEMPERATURE DEPENDENCE
SIZE
LENGTH
SATURATION
Yucca Mountain Project