Experimental studies on compaction of quartz – smectite mixtures and the response of porosity, density, P-wave velocity

Monday, 15 December 2014
Xiaosong Yang1, Yu Yang2 and Jinyu Chen1, (1)Institute of Geology, China Earthquake Administration, Beijing, China, (2)High Pressure and Temperature Laboratory, Faculty of Geoscience, Utrecht University, Utrecht, Netherlands
The density (ρ), porosity (φ) and P-wave velocity (Vp) of quartz – smectite mixtures were systematically measured as a function of pressure from 10MPa to 450 MPa on oedometer at room temperature. A new approach was developed to determine total porosity of materials as function of loading. The total porosity can divided into two portions, compliant porosity (φc(P)) and framework one (φr(P)). The former is well fitted by exponential function and reaches zero at the pressure Pcp – “compliant pore closure pressure”, and the latter described by a linear function. An interesting and startling phenomenon is that framework pores can survive in specimens beyond 450 MPa, even higher than 1000MPa. ρ and Vp linearly increase with pressurization at pressures beyond Pcp, however, the pressure derivatives of density (Dρ) and of velocity (Dv) are at least one order of magnitude higher than the counterparts of crystallized rocks. We attribute these higher values (Dρ and Dv) to the existence of pores within specimens even when pressure reaches 450 MPa.