Consolidation of water saturated shales at great depth under drained conditions

The principles of critical state mechanics appear to apply for shales. The isotropic consolidation behavior of four shales have been investigated experimentally at effective pressures of 1 to 65 MPa to evaluate some critical state parameters as a function of mineralogy and porosity. Sample volume change as a function of effective pressure was measured to determine the normal consolidation (NCL) and over consolidation (OCL) lines. The slopes of the NCL and OCL (λand κ) are distinct for the four shales. The slopes of the NCL correlate strongly with porosity and with the sum of porosity and swelling clay content, i.e. the water sources. The slopes of the OCL correlate with non-swelling minerals (clays and…