Evaluation of Groundwater Leakage into a Drainage Tunnel in Jinping-I Arch Dam Foundation in Southwestern China: A Case Study

Abstract

The Jinping-I double-curvature arch dam, located in the middle reach of Yalong River and with a maximum height of 305 m, is the world's highest dam of this type that has been completed. Since the second stage of reservoir impounding, after which the reservoir water level was gradually raised by about 232 m, a significant amount of leakage was observed from the drainage holes drilled in the lowest drainage tunnel at the left bank abutment at an elevation of 1595 m a.s.l. (above sea level), with an observed maximum pressure of about 0.3 MPa. A number of investigations, including water quality analysis, digital borehole imaging, tunnel geological mapping, and in situ groundwater monitoring, were performed to examine the source of leaking, the groundwater flow paths, and the performance of the grouting curtains. By defining two objective functions using the in situ time series measurements of flow rate and hydraulic head, respectively, a multiobjective inverse modeling procedure was proposed to evaluate the permeability of the foundation rocks that was underestimated in the design stage. This procedure takes advantage of the orthogonal design, finite element forward modeling of the transient groundwater flow, artificial neural network, and non-dominated sorting genetic algorithm, hence significantly reducing the computational cost and improving the reliability of the inversed results. The geological structures that lead to the leakage were identified and the seepage flow behaviors in the dam foundation and the left bank abutment were assessed. Based on the field measurements and the inverse modeling results, the effects of the engineering treatments of the leakage event on the dam safety were analyzed. It has been demonstrated that the seepage control system is effective in lowering the groundwater level and limiting the amount of seepage in the dam foundation, and the leakage event does not pose a threat to the safety of the dam.

A Normal Cloud Model-Based Method for Risk Assessment of Water Inrush and Its Application in a Super-Long Tunnel Constructed by a Tunnel Boring Machine in the Arid Area of Northwest China

“…where w i is the weight of the ith assessment index, M is the judgment matrix, n is the dimension of judgment matrix M, and λ max is the maximum eigenvalue of M. Finally, to ensure the accuracy of the results, the consistency of judgment matrix M should be verified by Formula (9).…”

“…Water inrush in tunnels is affected by many factors, such as hydrology, geology, and construction, and it is complex, fuzzy, and random. In recent years, many researchers and engineers have made great efforts to assess the risk of tunnel water inrush, and have developed various methods of analysis, including the geological analysis method [6], the analytic hierarchy process (AHP) method [7,8], the neural network method [9,10], the geographic information system (GIS) method [11,12], and the fuzzy synthetic evaluation method [13,14]. Although these methods provide a theoretical basis to analyze the risk of water inrush, there still have some shortcomings.…”

Seepage Characteristics and Its Control Mechanism of Rock Mass in High-Steep Slopes

“…As shown in Figure 13 [59,60], a multi-objective and whole-process dynamic inverse solution for analyzing seepage flow field was proposed based on orthogonal design, forwarding analysis of transient seepage, the BP neural network, and the non-inferior sequencing genetic algorithm. As to this approach: The fine precise simulation of the large drainage hole-curtain system and Signorinitype parabolic variational inequality method for transit seepage analysis are taken as the mean; the dynamic evolution of permeability and hydrogeological boundary conditions are taken as the parameters to be inversed; The optimal approximation of measured time series of data such as seepage pressure, water level and flow rate are taken as the objectives as follows [69],…”

“…266 m. Figure 13. Flowchart for multi-objective, full process dynamic inverse analysis [68][69][70].…”

The Importance of Detailed Groundwater Monitoring for Underground Structure in Karst (Case Study: HPP Pirot, Southeastern Serbia)

“…Complex geologic/hydrogeologic conditions require a comprehensive research approach to the interaction of groundwater and the water transported by a pressurized tunnel. Most studies dealing with this subject matter consider the problem of rapid groundwater inflow into a tunnel [4][5][6][7][8][9] and issues of structural stability [10,11]. In geological terms, the tunnel was built through the contact of two regionally important tectonic units (Getic and Danubian), which are represented by a system of east-vergent thrusts.…”