ABSTRACT
Inherent subjectivity in the most used rock mass classifications often causes accumulated inconsistencies between parameters mapped by different geologists which can lead to classification of the same rock mass into 3 different rock support classes. An alternative approach is to reduce the number of mapping parameters and focus on repeatability and geological consensus for rock mass classification. In this case study, scaled example pictures of the expected levels of blockiness and fracture condition were appended to the Geological Strength Index (GSI) chart. Direct comparison of these pictures to the rock mass determines the parameter values and reduces mapping time. Because the mapping process is quick, it can be repeated and verified more often. This pictorial GSI classification was tested on geologists and engineers and then used for rock support decisions on an open TBM. The resulting streamlined mapping process provided more consistency between all parties.
