Effect of roughness on the peak shear strength of clay infilled joints under constant normal stiffness

Asadul Haque, Buddhima Indraratna

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The shear behaviour of infilled joints produced from ordinary gypsum plaster (gyprock) and bentonite was investigated in the laboratory under Constant Normal Stiffness (CNS) conditions. Shear tests were performed on saw-tooth profiles having Joint Roughness Coefficients (JRC) of 4.75 and 9.25 under an initial normal stress (sno) of 0.30 to 1.10 MPa, and at a normal stiffness (kn) of 8.5 kN/mm. Test data under the same sno and infill thickness to asperity height ratio (t/a) were analysed for two different sets of JRC. The peak shear stress plotted against the t/a ratio under constant sno revealed an increase in peak shear stress with the increase in JRC, up to a t/a ratio of about unity. The effect of roughness on the peak shear stress was observed to be minimal when the t/a ratio exceeded 1.40. A mathematical model for the prediction of peak shear stress due to the increased infill thickness has been developed based on a hyperbolic stress-strain relationship and energy balance principles. The model predictions are in good agreement with the laboratory observations.

Original languageEnglish
Title of host publicationISRM 2003 - Technology roadmap for rock mechanics
EditorsM Handley, D Stacey
Place of PublicationJohannesburg South Africa
PublisherThe South African Institute of Mining and Metallurgy
Number of pages5
ISBN (Print)1919783520
Publication statusPublished - 1 Jan 2003
EventInternational Society of Rock Mechanics Series of Symposia and Conferences 2003 - Johannesburg South Africa, Sandton, South Africa
Duration: 1 Jan 200312 Sept 2003
Conference number: 10th


ConferenceInternational Society of Rock Mechanics Series of Symposia and Conferences 2003
Abbreviated titleISRM 2003
Country/TerritorySouth Africa
OtherInternational Congress on Rock Mechanics (ISRM 2003)

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