Hydro-geo-mechanical properties for water flow prediction in tunneling

Tunnelling projects often face challenges related to water inflow leading to operational safety issues, destabilisation, and increased costs. Accurate prediction of water flow is therefore critical. This study aims to provide guidance on how to achieve this goal by examining hydro-geo-mechanics principles for predicting water flow in tunnelling and highlighting the role of geology in rock mass discontinuities data collection. This study discusses the role of geology in rock mass discontinuities data collection. Understanding the geological setting is crucial for collecting appropriate discontinuities data. We present an overview of different data collection techniques, including information gathered from discrete and confined outcrops, and those collected from more continuous outcrops. It discusses data collection from borehole, hydraulic tests (e.g., Drill Stem Tests), and tracer tests, for 1D and 2D data to derive the rock mass zone. Furthermore, discontinuities statistical distributions for different rock types, such as stratified and non-stratified rocks, are discussed. The next aspect discussed in this study is fracture network attributes such as connectivity, transmissivity, and permeability. Connectivity and transmissivity of discontinuities can be used to derive the permeability tensor from discontinuities data in rock masses. The study provides details on how to use the fracture network data to derive estimation of the permeability tensor from, including a comparison of different methods, In conclusion, this study provides insights into hydro-geo-mechanics principles for predicting water flow in tunnelling. The discussion on discontinuities data collection, statistical distribution, and permeability tensor derivation provides valuable information for tunnel engineers to accurately predict and control water flow during tunnel excavation. The study emphasises the importance of considering the hydro-geo-mechanical behaviour of the rock mass in predicting water flow and provides a comprehensive understanding of the various techniques used in the process.