Mechanical properties of siliceous rocks around Horonobe URL from triaxial compression and isotropic consolidation tests

Sanada, Hiroyuki; Matsui, Hiroya ; Fujii, Yoshiaki*

This paper shows the results obtained from triaxial and isotropic consolidation test to select mechanical behavior of Horonobe siliceous rocks. The consolidated undrained and drained triaxial compression tests showed different behaviors of strain-softening, pore pressure and dilatancy between diatomaceous and siliceous mudstones. Stress-strain behavior changed from strain-softening to ductile behavior under high confining pressure and pore pressure increased gradually even after peak strength for diatomaceous mudstone. Diatomaceous mudstone yielded under hydrostatic pressure of 10 MPa in isotropic consolidation test. This yielding was regarded as pore collapse based on the variation of hydraulic conductivity which was estimated from variation of volumetric strain in isotropic consolidation test, effective porosity and microscopic observation before and after the yielding.