Abstract

The fluctuation of water levels in large reservoirs has long been recognized as a critical external factor that affects the stability of bank slopes. However, there have been limited studies investigating the influence of reservoir water level (RWL) fluctuation on anti-dip layered rock slopes. In this study, we constructed a conceptual model by selecting the sandstone in the Three Gorges Reservoir Area (TRGA) as the strata and considering variations in strata thickness, strata dip angle, permeability coefficient, RWL fluctuation rate, and slope height. Through seepage-stress field coupled analysis, we obtained the seepage field and groundwater lines, and determined the factor of safety (FoS) using the improved cantilever beam limit equilibrium method. We then investigated the variations of the groundwater line and FoS throughout the entire process of RWL rising and drawdown. Our results indicate that the changes in groundwater levels in the slope clearly lag behind RWL fluctuations, with stability improving during the rising stage but deteriorating during the drawdown stage. Range analysis, using the maximum curvature (MaxCurve) of the groundwater level line as the reference, reveals that the permeability coefficient has the most significant impact on the lagging effect, followed by the fluctuation rate, thickness, and dip angle. Similarly, when considering the amplitude of variation in FoS during the entire process of RWL rising and drawdown as the reference, range analysis shows that the permeability coefficient has the greatest impact on stability variation, followed by the fluctuation rate, thickness, dip angle, and slope height.

Abstract

To address the issue of balancing complexity and accuracy in existing analytical solutions for seepage fields, this study considers the influence of lining thickness and employs the method of images to obtain analytical solutions for the seepage field in deeply buried underwater tunnels. The advantage of this solution lies in its simplicity and relatively high accuracy. Building upon this, the seepage field is applied to the equilibrium equation of the lining in the form of volume forces, and the stress solution for the lining is obtained using the stress function method. Furthermore, the validity of the analytical solution is established by examining tunnel engineering cases and comparing them with existing solutions. The study's findings highlight that enhancing the impermeability of the tunnel lining effectively reduces water infiltration but leads to increased external water pressure on the lining. Moreover, the relationship between water inflow and external water pressure shows approximate linearity with the burial depth of the tunnel. Furthermore, as the lining's permeability decreases and the burial depth increases, the radial normal stress within the lining intensifies. Particularly noteworthy is the observation that the circumferential normal stress experiences a more rapid increase over distance.