Rock Physics Modeling of Dynamic and Static Youngfs Moduli of Soft Sedimentary Rocks
Toru TAKAHASHI and Soichi TANAKA
Abstract:To interpret dynamic and static Youngfs moduli of soft sedimentary rocks, the Dvorkin-Gutierrez silty shale model, one of granular models is applied to the measured Youngfs moduli obtained from velocity logging data for the dynamic modulus and from laboratory mechanical test data for the static modulus. The Youngfs modulus for the rock is calculated by the Hashin-Strikman lower bound, Hertz-Mindlin contact model and Gassmannfs equation. For modeling static Youngfs modulus, in the Hertz-Mindlin contact model, the shear modulus is calculated by incorporating the mixture of frictional and frictionless grain contacts into the model. The calculated dynamic and static Youngfs moduli are well consistent with the measured data for three different soft sedimentary rocks in Japan. This result demonstrates that the rock physics model can be used to predict the static moduli required in civil engineering applications from dynamic ones obtained from seismic velocities. Key Words:Rock physics, Geophysics, Dynamic and static youngfs moduli, Soft sedimentary rock, Dvorkin-gutierrez silty shale model, Granular model