Liquefaction Evaluation Spreadsheet

 

This spreadsheet identifies possible zones of liquefaction in a soil profile. It compares the anticipated cyclic shear stresses induced by an earthquake to the esitmated cyclic strength of the soil. Zones where the induced stress is greater than the cyclic strength are deemed zones of liquefaction.

The methodology involves two distinct processes:
1. Compute the equivalent cyclic shear stress induced by an earthquake vs. depth
2. Compute the cyclic shear strength of the soil profile

Step (1) can be accomplished in many ways, however the simplest is the method developed by Seed and Idriss (1971) where induced stresses are determined by earthquake magnitudes and depth of the soil deposit. Other methods include field correlations by authors on site-specific earthquakes, or 1-D wave propagation analysis by computer (Shake, MocEQ1).

Step (2) is most-easily done by correlating cyclic strength to corrected SPT blow count. Alternatively, CPT data, laboratory data, and other measures of soil cyclic strength can be used.

 

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