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Tunnel excavation in mountainous region frequently encounters high local inflows as a consequence of hydraulic head and multiple faults geology, which may adversely affect the serviceability of tunnel structures. Previous researches, however, paid very little attention to the seepage field of rocks around deep buried tunnels adjacent to water-beari...
Citations
... Numerous researchers have studied how tunnel construction affects the groundwater environment [2][3][4][5][6][7][8][9][10]. Underground engineering and construction disturb the groundwater environment and lead to decreases in the water resources across wide geographical areas and over considerable time periods; in some cases, the effects are irreversible and the groundwater does not recover [11][12][13][14][15]. ...
The tailwater tunnel of the Wuyue pumped storage power station is located in bedrock and extends to depths between tens and hundreds of meters. It is impossible to analyze and evaluate the whole engineering area from geological exploration data, and the hydrogeological conditions are complicated. In the early stages of the tailwater tunnel’s construction, the drinking water wells in four villages dried up. This paper reports the results from a field investigation, in situ tests, laboratory tests, and numerical simulation carried out to determine how the groundwater was affected when the tunnel was excavated. A hydrogeological model of the region was established from the inverted regional natural flow field parameters. The model was validated, and an analysis of the errors showed that there was an average error of 1.98% between the natural flow field and the hydrogeological survey flow field. The model was then used to simulate the three-dimensional transient seepage fields under normal seepage conditions and limited seepage conditions, as far as was practical. The results showed that, as the excavation of the tailwater tunnel advanced, the water inflow to the tunnel also increased. When the water inflow increased from 1000 to 5000 m3/d, the water level at a distance of 100 m from the axis of the tunnel dropped from −0.956 to −1.604 m. We then analyzed how the water level changed as the water inflow varied and proposed a formula for calculating the extent of the influence on the groundwater. We studied how the water level changed at different well points to ascertain how a groundwater well became depleted and determined the factors that influenced seepage in the regional flow field. The water level in different areas of the project area was simulated and analyzed, and the extent of the groundwater area affected by the tunnel construction was clarified. We then studied how the groundwater in different areas of, and distances from, the project area was influenced by normal seepage conditions and limited seepage conditions and proposed a formula for calculating the extent of the influence on groundwater for different water inflows. We constructed a ‘smart site’ for visualizing data, sharing information, and managing the project. Time–frequency domain analysis was applied to explore the extent of the impacts and range of the vibration effects on residential housing at different distances from the project area caused by the different methods for excavating the tailwater tunnel. The results from this analysis will provide useful insights into how the excavation of this tailwater tunnel will impact the local residents and living areas.
... Considering each position of a tunnel located in water-rich fault zones, Zhang et al. (2021) propose the following relationship between groundwater inflows (Q) and hydraulic head (H): ...
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.
