Discussion on “Empirical methods for determining shaft bearing capacity of semi-deep foundations socketed in rocks” [J Rock Mech Geotech Eng 6 (2017) 1140-151]

A new comprehensive set of data (n = 178) is compiled by adding a data set (n = 72) collected by Arioglu et al. (2007) to the data set (n = 106) presented in Rezazadeh and Eslami (2017). Then, the compiled data set is evaluated regardless of the variation in lithology/strength. The proposed empirical equation in this study comprises a wider range of uniaxial compressive strength (UCS) (0.15 MPa < σrc < 156 MPa) and various rock types. Rock mass cuttability index (RMCI) is correlated with shaft resistance (rs) to predict the shaft resistance of rock-socketed piles. The prediction capacity of the RMCI versus rs equation is also found to be in a fair good agreement with the presented data in Rezazadeh and Eslami (2017). Since the RMCI is a promising parameter in the prediction of shaft resistance, the researchers in the rock-socketed pile design area should consider this parameter in the further investigations.