Above-mentioned authors derived an equation for determination of rock mass modulus based on back-analyses (among other investigations) of tunnel excavations. Does this mean that Erm is unloading modulus?
Kind regards,
Zoran
Zoran! Good question but I do not think it matters much as the two equations connected to these authors have 'the freedom of D' so almost any desired result can be obtained for the higher GSI values. See very recent review '40 years of GSI' or very similar title, and a keynote I just delivered also in RG. In both you will see the unhelpful modulus predictions related with GSI. Another problem is that the depth or stress dependence is ignored in the two equations.
I fully agree with Nick. The GSI is a manipulative number which has no good base on the rock mass. In addition, one can-not use this equation which was based on a single case in Tiwan to estimate Erm in all projects around the world where completely different engineering geological conditions prevail.
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