抄録
The deformation characteristics of rock-like materials with different porosities have been studied experimentally using the specimens of cement mortar and tuff under triaxial compression states. The stress and strain are dealt with respectively by dividing into their isostatic and deviatoric components, and the experimental results are considered from a point of view of continuum mechanics. The results are as follows:
(1) The deformation characteristics of the porous rock-like materials depend essentially upon the variation of form of microscopic structure with the stress history.
(2) The stress-strain relationships of these materials under the isostatic stress are represented approximately by a bi-linear curve and its bending point may be considered as the yield point for the hydrostatic pressure.
(3) In the state of normal compression, the amount of recoverable shearing strain γoct varies in proportion to τoct up to the yield point and its rate of variation does not depend on the mean stress σm.
(4) In the state of normal compression, the contractancy arises with the increase of shearing strain under the constant mean stress and its magnitude increases with the mean stress.
(5) In the state of over compression, the slope of τoct-γoct curve up to the yield point is steeper than one in the state of normal compression, and the slope does not depend upon the normal stress.
(6) In the state of over compression, the contactancy is smaller than one in the normal compression and the dilatancy arises when the mean stress is relatively small.
The deformation characteristics of rock-like materials mentioned above may be explained reasonably by assuming the end cap-shaped yield surface in hardening for the yield condition of materials.
