Mechanical characterization of densely welded Apache Leap tuff

Abstract

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Borehole stability in densely welded tuffs

“…sive strength of this block sample and is about four times larger than the uniaxial compressive strength obtained by using the ASTM (D2938) standard method (i.e. 73 MPa - Fuenkajorn and Daemen, 1991). A similar discrepancy has been observed in borehole breakout experiments on different rock types by Daemen and Fairhurst (1971) and by Guenot (1987Guenot ( , 1989).…”

“…this maximum applied stress, the elastic solution gives a tangential compressive stress, at the borehole wall, of 8 4 MPa. This compressive stress exceeds the average uniaxial compressive strength of the tuff, given by Fuenkajorn and Daemen (1991) as 73 MPa. The relationship between the applied stress and the resulting strain seems to be linear for all loading cycles.…”

“…Apache Leap tuff exhibits a nonlinear behavior near the peak stress or failure (Fuenkajorn and Daemen, 1991), and that the shape and size of the rock subjected to critical stresses in the breakout zones changes with stress ratio. The latter explanation relates to the effect of size and stress gradient on the rock strength (Jaeger and Cook, 1979, pp. This could be due to the fact that…”

“…After plug installation, the swelling pressure exerted by the plug could induce radial cracks or could open or widen preexisting cracks in the rock at the bottom of the breakouts where the tangential compressive stresses induced by the stressfield have been released by the breakout process. Finally, the effect of the high intrinsic variability of tuff properties (krenkajorn and Daemen, 1991) on the design of underground openings is of concern. Determination of the opening stability in such rock based upon one set of properties is questionable.…”

“…66-69) give the location near the Nevada Test Site where the Topopah Spring tuff samples have been obtained. Fuenkajorn and Daemen (1991) give the mechanical and petrographical properties of both tuffs and discuss similarities and differences between the rocks.…”