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An experimental study of the mechanism of failure of rocks under borehole jack loadingLaboratory and field tests with an experimental jack and an NX-borehole jack are reported. The following conclusions were made: Under borehole jack loading, a circular opening in a brittle solid fails by tensile fracturing when the bearing plate width is not too small. Two proposed contact stress distributions can explain the mechanism of tensile fracturing. The contact stress distribution factor is a material property which can be determined experimentally. The borehole tensile strength is larger than the rupture flexural strength. Knowing the magnitude and orientation of the in situ stress field, borehole jack test results can be used to determine the borehole tensile strength. Knowing the orientation of the in situ stress field and the flexural strength of the rock substance, the magnitude of the in situ stress components can be calculated. The detection of very small cracks is essential for the accurate determination of the failure loads which are used in the calculation of strengths and stress components.
Document ID
Document Type
Van, T. K. (California Univ. Berkeley, CA, United States)
Goodman, R. E. (California Univ. Berkeley, CA, United States)
Date Acquired
August 6, 2013
Publication Date
July 1, 1971
Publication Information
Publication: Lunar Surface Eng. Properties Expt. Definition, Vol. 3
Subject Category
Distribution Limits
Work of the US Gov. Public Use Permitted.

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