Abstract
During the review of the published technical literature regarding the uses and limitations of the GSI index (Hoek, 1994; Hoek et al., 1995) for the geomechanical characterization of rock masses, it has been observed that some recommendations regarding the reduction or adjustment of the GSI for scale effects have already been indicated in previous studies.
The most notable is by Hoek et al. (2013), who, referring to the GSI chart, stated: "This chart applies to tunnels approximately 10 m in span and slopes less than <20 m in height. For larger caverns and slopes, consider reducing the GSI to account for the decrease in block interlocking." On the other hand, Sonmez et al. (2021) indicated that: "When the engineering dimension (slope height or tunnel span) increases, a decrease in the GSI should be expected," and that "the GSI is a scale-dependent parameter." However, since these publications do not suggest how to perform the mentioned GSI adjustment, it is generally not applied in geotechnical analyses.
Considering this issue, in recent years, some practical criteria have been published to simply include the effects of GSI adjustment based on the scale of analysis, such as the "Equivalent GSI" (Pozo, 2022) and the "Equivalent Dimension GSI" (Sonmez et al., 2024), which modify the GSI based on the characteristics and dimensions of the excavations. These criteria consider in their formulation geometric parameters (slope height, etc.) and/or geomechanical parameters of the rock mass (fracturing, strength, joint condition, etc.).
Consequently, the objective of this research is to review and compare the results of the application of both mentioned approaches, studying their scope of application, as well as the parameters involved in their formulation, the reduction from the perspective of the rock mass structure, and the joint condition. For this purpose, 8 real slopes located in Peru, Turkey, and Mexico have been analyzed, calculating the adjusted GSI values in each case using a proprietary web application (beta version).
Date: Friday, December 6, 04:30 - 04:50 PM, Session 4
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