This document details Datarock’s product Geotechnical Strength Index (GSI) Proxy.
The literature, "Quantification of the Geological Strength Index Chart," introduces a structured approach to quantifying the Geological Strength Index (GSI), transforming the traditional qualitative assessment into a more standardised quantitative evaluationGeological Strength Index (GSI) was introduced in the early 1990s as a means to quantify and characterise the strength and deformability of rock masses for engineering and geotechnical applications. It was identified there was a need for a standardised index that could reliably assess the rock mass behaviour and provide valuable insights for construction and excavation projects. GSI takes into account various geological parameters such as rock structure, weathering, and joint conditions, assigning a numerical value to represent the overall strength and deformability of the rock mass.
Datarock has developed this product to extract as much information as possible from the core image, however it is named GSI Proxy for two key reasons:
Recognition of the fact that it is pushing the limits of what is achievable from a core photograph; and
It is not possible to reliably determine joint infill rating from a core photo.
Contents
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The Roughness Rating is determined using Datarock’s Joint Roughness Coefficient as its basis (see JRC product description for details).
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The JRC values are converted to a 0-6 scale using the following polynomial function (established by fitting a polyline to empirical data):
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GSI Calculation from the Quantified Chart
The GSI value is determined by digitising the GSI plot on the surfer and obtaining the surface equation (a quadratic-second order surface). With the calculated x (SCR) and y (SR) coordinates on the GSI chart, these values are plugged into the surface equation to yield the GSI value, providing a quantified measure of the rock mass quality.
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This method provides a systematic approach to quantifying the GSI by integrating various rock mass characteristics, as detailed in the paper. The use of empirical relationships and polynomial functions allows for a more objective and quantifiable assessment of the GSI, contributing to a standardised evaluation of rock mass conditions.
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