Strain energy based evaluation of liquefaction and residual pore water pressure in sands using cyclic torsional shear experiments

• Published in: Soil dynamics and earthquake engineering (1984) 2012-04, Vol.35, p.13-28
• Main Authors: Jafarian, Y., Towhata, I., Baziar, M.H., Noorzad, A., Bahmanpour, A.
• Format: Article
• Language: English
• ISSN: 0267-7261; 1879-341X
• DOI: 10.1016/j.soildyn.2011.11.006

In this study, cyclic hollow cylinder torsional tests were conducted on the reconstituted specimens of Toyoura sand in a practical range of initial density and stress states. The results were employed to evaluate the liquefaction resistance and residual pore water pressure of sand using the strain energy concept. A simple pore water pressure (PWP) model with two calibration parameters was developed for the prediction of residual pore pressure as a function of cumulative strain energy density and the capacity energy of sand. Capacity energy is defined as the cumulative strain energy that is required for liquefaction onset. Based on the results of the tests, an equation is then presented for the estimation of capacity energy in terms of relative density and initial effective confining pressure of sand. This equation is shown to work well as a state boundary curve, which can discriminate between the liquefied and non-liquefied field case histories. Several extra tests were also performed to investigate the effect of initial static shear stress on the proposed PWP model and capacity energy. The results show that initial shear stress has a minor effect on the trend of the proposed PWP model; however, it definitely affects the capacity energy. The final part of the paper aims to confirm reasonable performance of the proposed PWP model by the available observations of seismically induced pore water pressure in shaking table, centrifuge, and real site conditions. ► We present a lab-based model to evaluate seismic pore pressure in soils via strain energy concept. ► The developed model is shown to be independent of the variations of initial shear stress. ► Investigation is carried out on capacity energy, which is the most important calibration parameter of the model. ► A lab-based capacity boundary is presented as a discriminator between liquefaction and no-liquefaction conditions. ► The proposed model is validated using centrifuge, shaking table, and field observations.