Constitutive Equations for Rocks, Based on Radial Stiffness Decrease

Yoshiaki FUJII and Yoji ISHIJIMA

Division of Structural and Geotechnical Engineering, Graduate School of Engineering, Hokkaido University, Kita-ku, Sapporo 060

J. of MMIJ, Vol.114, No.3, p.169-174 (1998)

A linear equation between axial strain, circumferential strain and axial stress was found while performing compression tests on several kinds of rock. This equation means that in such laboratory tests the trace of axial strain, circumferential strain and axial stress is located on a plane in the three-dimensional space defined by these quantities. New constitutive equations were derived combining the above-mentioned equation with another equation which derived assuming that the stiffness in the radial direction decreases with radial expansion. Using the set of the newly-deduced constitutive equations, the effect of confining pressure on strength and strain-softening behavior including Class II can be simulated. Numerical results also show the decrease in radial stiffness due to crack existence.

KEY WORDS: Rock, Constitutive Equations, Radial Direction, Stiffness

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