Quantitative Assessment of Cut-off Wall Effects on Seepage and Leakage in Earth-Rockfill Dams
摘要
To address seepage control in earth-rockfill dams founded on deep overburden layers, an earth-rockfill dam on a deep overburden foundation in Yunnan Province was selected as the engineering case. Based on a finite-difference seepage calculation model, the effects of a cut-off wall on the spatial distribution of the seepage field and variations in leakage volume were systematically investigated. The reliability of the numerical model was verified using field monitoring data, and sensitivity analyses were conducted under different permeability coefficients and operating water levels. The results indicate that the cut-off wall significantly altered the spatial distribution of the seepage field and effectively suppressed seepage through the dam body and shallow overburden layer. However, its control effect on seepage through the deep overburden layer was relatively limited, and deep seepage remained an important contributor to the overall leakage. After the cut-off wall was installed, the total leakage volume was reduced from 149.16 × 104 to 82.69 × 104 m3/year, corresponding to a reduction of approximately 44.5%. The leakage volumes through the dam foundation, dam abutments, and dam body were reduced by 39.4%, 50.9%, and 52.4%, respectively. Good agreement was observed between the field monitoring results and the numerical simulation results, with relative errors of 6.5% and 3.3% for the total leakage volume and dam-body leakage volume, respectively. The sensitivity analysis results show that, under different permeability coefficients and stable operating water levels, the seepage-control pattern and leakage-reduction effect of the cut-off wall remained relatively stable. The findings can provide a reference for the optimization of seepage-control systems and seepage safety assessment of earth-rockfill dams founded on deep overburden layers.