CSIRO Triaxial Stress Measurement Cell

Measurement-related uncertainties in overcoring data at the Äspö HRL, Sweden. Part 2: Biaxial tests of CSIRO HI overcore samples

“…[32]). The 9-gauge cell is supplied with two axial ð z Þ, three tangential ð y Þ, and four from the axial direction inclined 7451 strain gauges ð 45 and 135 Þ.…”

“…where y is the orientation of the strain gauges in the borehole according to the chosen coordinate system; E is the Young's modulus; n is the Poisson's ratio (E and n are determined from biaxial tests); and K 1 -K 4 are correction factors [32][33][34][35] representing the situation that the strain gauges are not in direct contact with the rock surface, and for the deformation resistance of the CSIRO HI cell [32,33]. The correction factors are generally close to one and do not significantly affect the calculated stresses [32].…”

Stress Field of the Earth’s Crust

“…7 and 8 assume elastic, isotropic, homogeneous rock material. There is uncertainty, however, when the analysis breaks down for anisotropic rocks in terms of the modulus ratio (Worotnicki 1993;Amadei 1996;Hakala et al 2007). Dight and Dyskin (2008) determined anisotropic rock moduli by testing small subcores drilled in different directions (cf.…”

Three-dimensional finite element modelling of stress relaxation tests in anisotropic clayey medium: direct problem and back analysis

“…According to Worotnicki (1993), it consists in choosing an axial distance before and after the cell of at least 2D, where D is the diameter of the access borehole. In the simulations, this distance depends on the geometry of the test considered, but the condition is always verified.…”

“…One can find analytical solutions in Duncan-Fama and Pender (1980) and Worotnicki (1993). Nevertheless, a rock mass is hardly an elastic medium and exhibits non linear phenomena, such as plasticity or damage.…”