I am modeling tailing dams in plaxis and i need to obtain the CRR or CSR value to plot it versus the N1,60 value and generate the CRR or CSR V/S N1,60 value.
Thanks and regards to all
Dear Sebastián,
The concepts of cyclic stress ratio (CSR) and cyclic resistance ratio (CRR) are used by semi-empirical procedures (e.g. Seed and Idriss, 1971; Youd et al., 2001; Idriss and Boulanger, 2014), aiming at estimating a factor of safety (FS) against soil liquefaction: FS = CRR / CSR.
The CSR involves the transformation of given earthquake-induced stresses into an “equivalent” series of shear stress cycles with uniform amplitude. According to the semi-empirical procedures, CSR can be computed at a given level of the deposit as: CSR = 0.65 tau-max / sigma’v0, where tau_max is the maximum earthquake-induced shear stress and sigmav’0 is initial vertical effective stress. Providing that the shear stress time-history at a given level is obtained, it is possible to determine tau_max and, given the initial vertical effective stress, to compute CSR.
Dear Stefanos,
I read your answer. But there is one point I don't understand. How can I specify tau-max. I used PM4Sand in analysis. When I examined the analysis results, I could not obtain the tau-max you mentioned.
You will need to select some stress points at the start of the calculation. Plaxis will calculate the shear stress during the event and keep track of it at the points. When the analysis is completed you can use the curves to plot the shear stress at that point and get the maximum.
Martin
Thank you for your answer.
How can transform the pore water pressure ratio into Factor of Safety for that specific layer. My intention is to calculate Liquefaction Severity Number /Liquefaction Potential Index of a borehole