Constitutive relation for compressive loading in Nugget sandstone
Stress-strain data for Nugget sandstone (a quartz arenite with 4.1 percent porosity) over a variety of compressive stress states were examined by curve-fitting techniques. Purpose was to determine the existence and a form of a simple constitutive relation describing dilatant strain. The dilatant volume strain can be described by epsilon/sub v//sup e/ = a/sub 0/ + a/sub 1/ J/sub 2//sup /sup 1///sub 2// + b/sub 0/ exp (b/sub 1/J/sub 2//sup /sup 1///sub 2//), where epsilon/sub v//sup e/ is the difference between the measured volume strain and the hydrostatic volume strain at the same mean stress and the regression coefficients a/sub i/, b/sub i/ are functions of the first stress invariant. The increase in the dilatant strain with J/sub 2/, the second invariant of the stress deviator, is believed to be related to two mechanisms: (1) a ''differential crack closure,'' which involves the response of each crack with respect to orientation to the principal stresses, and (2) an exponentially divergent region due to the propagation of existing cracks. The boundary between nondilatant and dilatant behavior for a variety of loading paths is described fairly well by the curve in mean stress-shear stress space for uniaxial strain. The fracture surface is found to be independent of loading path. 8 fig.
- Research Organization:
- California Univ., Livermore (USA). Lawrence Livermore Lab.
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 7267001
- Report Number(s):
- UCRL-52036
- Country of Publication:
- United States
- Language:
- English
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