Compression index Cc

[ypyenpham]

Hi, everyone

In consolidation test, the same depth sample but compression index Cc before and after improved by PREFABRICATED VERTICAL DRAINS (PVD)is little change or no change. Although after improved by PVD, water content decrease and unit weight increase.

Everyone can explain to me. Why do compression index Cc no change?

Thanks!

 

[geoman110]

I assume you preloaded the site with PVD. All PVD does speed up the drainage. The stress condition before and after application of soil improvement (preload) moves along the virgin compression line. Therefore, if you take a sample before and after preload and test it the Cc should be the same order of magnitude (not necessary the exact same). On the other hand, if you remove the preload and sample the clay for consolidation test, the post soil improvement sample should show you a different pre-consolidation pressure.