A study on groundwater inflow during tunnel excavation in hard rock

Abstract

This paper mainly studies the phenomenon of groundwater inflow into deep tunnels. First, we analyzed the key and difficult points of hydrogeological problems in underground tunnel engineering, and discussed the methods for predicting groundwater inflow at different scenarios, including analytical methods, empirical methods, numerical methods, and some lately emerging machine learning methods. It compared the advantages and disadvantages of each method and proposed that the best method for groundwater prediction is to use different methods in the early, middle and late stages of tunnel excavation. Then, this paper discussed different methods for controlling groundwater, including concrete lining structures, pre-excavation grouting (PEG), and post-excavation grouting, with focus on the increasingly popular method of PEG covering its principles, processes, material selection and parameter design, and monitoring methods of PEG. Finally, an example of a completed deep sewage tunnel project in Hong Kong, the Harbour Area Treatment Scheme Stage 2A (HATS 2A), is used to illustrate that PEG is currently one of the most effective methods for controlling groundwater influx. Finally, we summarized the methods for groundwater prediction and control, and proposed new prospects, such as using new low-carbon, green and environmentally friendly materials for grouting, using new AI technology to monitor the grouting process, so as to ensure both economics and safety, as well as sharing international standard technologies and parameters, and conducting extensive economic exchanges.