Regression Analysis of Q- Value Data for Shale Rock in Tunnels: Implications for Support System Design

Abstract:

The Q-system, developed by Barton et al. (1974), is a widely used rock mass classification system that provides a quantitative measure of rock mass quality. The Q-value, which ranges from 0.001 to 1000, is calculated based on six parameters: rock quality designation (RQD), joint set number (Jn), joint roughness number (Jr), joint alteration number (Ja), joint water reduction factor (Jw), and stress reduction factor (SRF). These parameters collectively capture the rock mass's geological and geotechnical characteristics, enabling a comprehensive assessment of its stability.The Q-value serves as a reliable indicator of rock mass quality, allowing engineers to predict potential stability issues and design appropriate support systems. A higher Q-value indicates better rock mass quality, while a lower Q-value suggests poorer quality and increased support requirements. By using the Q-system, engineers can optimize tunnel design and construction, reducing the risk of instability and associated costs.The predictive model developed in this study further enhances the utility of the Q-system by enabling the estimation of Q-values based on shale properties which allows engineers to anticipate rock mass behaviour and design support systems, accordingly, streamlining the tunnel construction process. The model's accuracy and reliability make it a valuable tool for tunnel designers and engineers working in weak shale formations. By leveraging the Q-system and predictive model, engineers can improve tunnel stability, reduce construction costs, and enhance overall safety.

• Periodical: Engineering Headway (Volume 34)
• Pages: 73-90
• DOI: https://doi.org/10.4028/p-2LxUeK
• Online since: February 2026
• Authors: Mahananda Dutta*, Sanket Tirpude, Sandeep Potnis
• Keywords: Construction, Q-System, Regression Analysis, Rock Mass Classification, Tunnel Design, Tunnelling, Weak Shale Rock

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