## 6 A Discussion of the Qualitative Aspects (Joint Conditions) of Existing GSI Charts  
For completeness, a discussion of the horizontal axis of the V-GSI chart is provided in this section of the paper given that this also formed of part of the general criticism of quantified GSI charts by [1], as discussed in the introduction. Descriptions or qualitative assessments for Q or RMR classification systems, and used in most GSI charts, including the V-GSI chart to assess discontinuity conditions, is not true quantification. With respect to GSI, this is because to date there has been no other easy way to improve or quantify discontinuity conditions on the horizontal axis. An assessment is nonetheless a necessity--descriptive or otherwise. In the context of GSI, none of the charts to date address the real quantification of the horizontal axis. It is implicit in the original graphical chart (Figure 3) that GSI ratings on the horizontal axis decrease as the surface quality decreases by around 15 points per surface quality descriptor, depending to a limited degree on which structure caricature is selected on the vertical axis. In GSI charts that use 1.5 [Cond89 [3,21] (see Figure 6), on the horizontal axis, ratings generally decrease by around 10 points for each rightward shift in surface quality descriptor for a given structure. [PERSON] and [PERSON] revised the GSI chart [1] (provided as Figure 8, pg. 14 in ref. [1]) chart, which essentially retains the same shift of around 10 points on the horizontal axis for each shift in the surface condition descriptors. there is a. As presented by the authors of [3], it is \"recommended that, where possible, discontinuity surface conditions should be established first independently using descriptors that fit the observed discontinuity conditions for a particular project or geological environment and that the central tendency or modal frequency of observation bins or measurements be established first\". This is because, if, for example, the JCond89 system alone is used, this can result in the misinterpretation of natural trends in rock masses--rather where possible, quantitative measurements and qualitative observation should be recorded and statistically characterized fist to determine representative joint conditions--per discontinuity set preferably for a given structural domain. Assessed and representative conditions can then be fitted into JCond89 bins (where possible), and an overall rating can be obtained for JCond89 as used in the V-GSI chart.\"  
An example of this type of characterization that can be undertaken to establish modal frequency or central tendencies for discontinuity observation and measurement is shown in Figure 10, noting that the parameters shown are not the only parameters that can or should be assessed. The next sections of this paper provide two case histories and some updates that demonstrate that the methods used to quantify the vertical axis on the V-GSI chart using joint spacing data and joint persistence data do provide reliable P30 and P32 estimates, which in turn can provide reasonable strength and deformability estimates for a rock mass. Canal Route in Rock, Italy: Comparisons of P32 Estimates Using a New Method by [PERSON] (2024) [29], DFN Modelling, and the V-GSI Method  
In a recent paper by [29], summary data were provided from an excavation in rock for a canal route. [PERSON] states that the data were collected over a stretch of about 50 m, where the rock mass was found to be fairly homogeneous--essentially in the same structural domain. According to [29], discontinuity data were sampled along 29 scanlines (16 longitudinal and 13 transverse to the canal axis), with lengths in the range 7-18 m. Table 2 (provided as Table 4 in ref. [29]) provides summary statistics from the field data that identifies four major discontinuity sets and includes the mean true spacings and associated standard deviations per set, and the mean size or diameters for each set, and the distribution type.