Enhancing Tunnel and Cavern Designs through Seismic Tomography and Numerical Ground Information Modelling (GIM) of Rock Mass Quality Data

Abstract

A robust site investigation is pivotal in the design of tunnel and caverns, and collected data often defines the characterization and parameterization of rock mass quality, interpretation of geological features, and understanding of constraints of deep weathering profiles and fault zones. Conventional geotechnical site investigations (SI) for such projects typically rely on intrusive methods, such as drillholes, which provide localized samples and data. However, the isolated nature of these drillhole locations necessitates the extrapolation of geological surfaces, often leading to challenges in accurately estimating the extent, trend, and impact of geological features on adjacent rock mass quality. To address these challenges, this study discusses how non-intrusive cross-hole seismic tomography can be used to enhance site investigations and as an input for developing integrated numerical modelling applications. This approach allows for more spatially complete evaluation of the lateral and vertical variability of rock mass quality at proposed tunnel and cavern sites. A notable aspect of this work is the exploration of correlations between seismic wave velocities and Rock Mass Quality Q-System as outlined by Grimstad and Barton (1993) and updated by Barton (2002). Additionally, the paper introduces methods for developing confidence intervals and Ground Information Models (GIM) of digital data trends. The paper also provides a review of the benefits and limitations of these methods, along with suggestions for enhancing the geostatistical prediction of rock mass quality.