Key factors influencing analytical solutions for predicting groundwater inflows in rock tunnels

Abstract

Predicting groundwater inflow into tunnels is essential to ensure the safe accessibility and stability of underground excavations and to attenuate any associated risks. Such predictions have attracted much attention due to their tremendous importance and the challenge of determining them accurately. Over recent decades, based on diverse methods, researchers have developed many relevant analytical solutions. Considering these research efforts, this article identifies and describes the most critical key factors that strongly influence the accuracy of groundwater inflow predictions in rock tunnels. In addition, it presents a synthesis of the latest advances in analytical solutions developed for this purpose. These key factors are mainly time dependency of groundwater inflows, water-bearing structures, aquifer thickness, hydraulic head and groundwater drawdown, rock permeability and hydraulic conductivity, fracture aperture, and rainfall data. For instance, groundwater inflows into tunnels comprise two stages. However, the transition between the stages is not always rapid and, for tunnels located in faulted karst terrains and water-rich areas, groundwater inflows can exceed 1,000 L/min/m. Under high stress, rock permeability can increase up to three times near the inevitable excavation-damaged zones, and groundwater inflows into tunnels can be significantly affected. Despite the enormous amount of research already conducted, improvements in the accuracy of predicting groundwater inflows into rock tunnels are still needed and strongly suggested. HIGHLIGHTS The main factors influencing the accuracy of prediction of groundwater inflows into tunnels are comprehensively highlighted.; Accurate prediction of groundwater inflows into tunnels is not yet fully resolved.; The great need to continually improve the accuracy of these predictions is discussed.; The latest advances in analytical solutions for forecasting these inflows are presented.; A process for selecting an appropriate analytical solution to assess groundwater inflows in a given rock tunnel is proposed.;

Keywords

• accurate prediction of groundwater inflows
• groundwater inflows
• key factors
• long-term stability of tunnels
• rock behavior