Effect of Existing Dams on Liquefaction Potential Analysis of Foundation Soils

In a typical seismic dam safety evaluation of an existing generally competent dam on potentially liquefiable foundation, SPT, CPT, BPT or Vs tests are often conducted in the vicinity of toes of dams to infer if any liquefiable soils may exist in the foundation of the dam footprint. In order to use the simplified procedure for liquefaction potential evaluation, the data from these field tests are normalized to a reference vertical overburden stress. In the current practice, "free-field" condition is generally assumed in the determination of normalized penetration resistance and shear wave velocity, neglecting rotation of principal stresses in soils in the vicinity of big structures. This paper attempts to incorporate these effects using a simple finite element model for a case of a generic earth dam. It is proposed that effective mean stresses be used while normalizing penetration resistances and Vs instead of vertical effective stresses based on free-field assumption. A simple finite element model can be used to estimate effective mean stresses under or in the vicinity of a structure.

Read More: http://ascelibrary.org/doi/abs/10.1061/40904(223)7