How is soil liquefaction potential evaluated?

Liquefaction evaluation compares cyclic stress ratio (CSR) induced by earthquake to cyclic resistance ratio (CRR) of soil. CSR = 0.65*(amax/g)*(sigma_v/sigma'v)*rd, where amax = peak ground acceleration, rd = depth factor. CRR is determined from SPT N-values or CPT tip resistance using empirical correlations. Factor of safety = CRR/CSR; FOS < 1.0 indicates liquefaction likely. Susceptible soils are loose, saturated sands with low fines content. Mitigation includes densification, drainage, or ground improvement.