Tensile Tests of a Fluid-Filled Poroelastic Core Sample : Theoretical Consideration

Abstract

The literature shows that nonlinear stress-strain curves have been obtained in tensile tests of an epoxy-coated hourglass-shaped rock specimen under confining pressures and concludes that this nonlinearity is caused in part by plasticity and mainly by nonlinear elastic behavior. However, in addition to these causes, some contribution of pore-fluid diffusion in a specimen is expected to occur. The hourglass-shaped specimen was examined in a previous paper. For a noncoated cylindrical specimen (core sample), the present paper analyzes the contribution of radial pore-fluid diffusion to nonlinearity and yields the same conclusion as that in the previous paper; that is, this apparent nonlinearity is small but not negligible. A formula is also given to estimate the bend of the stress-strain curve due to diffusion. Furthermore, stress-strain hysteresis curves are given for the same purpose.