The Geological Strength Index (GSI) system, proposed in 1994 by Evert Hoek, is used for the estimation of the rock mass strength and the rock mass deformation modulus. The GSI system concentrates on the description of two factors, rock structure and block surface conditions. The guidelines given by the GSI system are for the estimation of the peak strength parameters of jointed rock masses. There are no guidelines given by the GSI, or by any other system, for the estimation of the rock mass’ residual strength that yield consistent results. Another method is that defined in the work of Cole & Stroud whereby the basic strength, in

Newtons The newton (symbol: N) is the unit of force in the International System of Units (SI). Expressed in terms of SI base units, it is 1 kg⋅m/s2, the force that accelerates a mass of one kilogram at one metre per second squared. The unit i ...

, and the shear strength in Kg/cm2, can be estimated

empirically In philosophy, empiricism is an Epistemology, epistemological view which holds that true knowledge or justification comes only or primarily from Sense, sensory experience and empirical evidence. It is one of several competing views within ...

by varied responses to hammer, knife & finger nail.https://gndec.ac.in/~igs/ldh/conf/2009/articles/T11_08.pdf

References

Hoek, E. (1994) "Strengths of rock and rock masses" ISRM News Journal, 2(2): 4–16.

References

Further reading