Pore pressure as calculated by pressureDependMultiYield

[mlw]

Hi all,

I have been working on verifying the OpenSees materal (pressureDependMultiYield) against time histories of shear strain and excess pore pressure ratio of experimental data. So far I have examined 2 shaking table experiments (one dry and the other saturated and liquefiable), and a centrifuge experiment (saturated liquefiable).

What I am finding is that the OpenSees results are always an excellent match to the experimental exess pore pressure time history. However the shear strain response is usually always wrong! How can this be? The pressureDependMultiYield model (Yang, Z., Elgamal, A.-W. M., & Parra, E. (2003). A computational model for cyclic mobility and associated shear deformation. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 129(12), 1119-1127.) developed for OpenSees calculates changes in pore water pressure from the volume of dilation or contraction i.e. from the volume of shear strain. So how can OpenSees calculate the correct excess pore pressure from an incorrect strain?

Thank you for your time,

mlw