Discussion of “ Analysis of a Large Database of GCL - Geomembrane Interface

by Hoek et al. 2002 and which is related to blasting, caused damage and stress relief; it may also be considered in the estimate of rock mass modulus from intact rock modulus. The recommendations of “D” values for tunnel and slope applications were provided by Hoek et al. 2002 . Unfortunately, no guidelines were provided for deep foundation application. The discussers related the disturbance factor to weathering and degradation of rock during drilled shaft construction, which was not originally discussed by Hoek et al. 2002 . Slake may cause weathering of rock and separation of rock pieces away from rock mass during drilled shaft construction at I-85 site. However, it may not necessarily cause reduction of rock mass modulus since slake does not necessarily damage the rock mass, which still remains in place, or cause additional stress relief other than the stress relief due to excavation itself. It is certainly worthwhile to investigate the disturbance factor for drilled shaft installed in slake susceptible rock. 3. Thank you for pointing out the typographical error. A modulus value of 146 MPa was used for the I-40 short shaft at depth of 2.3 m.