Search Results (2)

Filters serve as critical facilities for ensuring the seepage stability of earth-rock dams and tailings dams; their failure poses severe threats to dam safety. Traditional filter design criteria are constrained by the diversity of soil types and fail to account for the influence of pore characteristics (e.g., constriction size) on the soil retention and hydraulic conductivity of filters. Design methods recommended in design codes only provide gradation envelope boundaries without specifying exact gradation curves. This paper proposes a filter design approach based on the natural clogging concept. Using Terzaghi’s interlayer coefficient as the initial parameter, this method induces stable clogging layers of base soil within the filter through sediment-laden seepage, adopting the post-clogging gradation as the design gradation. Experimental results demonstrate that: (1) when the initial interlayer coefficient α of the filter is ≤10.4, the base soil retention rate exceeds 97% (soil loss < 3%), surpassing the conservative limit of α < 4 in Terzaghi’s criterion; (2) the final interlayer coefficient α of filters ZS-2 to ZS-5 ranges between 1.15 and 2.48, with i_b/i_f values between 6.26 and 23.68, simultaneously satisfying Terzaghi’s requirements for soil retention and hydraulic conductivity; (3) this method explicitly defines the specific gradation curve of the filter, with the final gradation curve of ZS-5 largely falling within the envelope recommended by design codes. The proposed method integrates Terzaghi’s interlayer coefficient criterion with the influence of pore characteristics on filter performance, offering a new design strategy for tailings dam filters with fine-grained base soils, preliminarily validated under laboratory conditions. Full article

Against the backdrop of global water scarcity, utilizing sediment-laden river water for agricultural irrigation is a critical strategy for ensuring food security. However, the associated water and nitrogen transport processes are influenced by the coupled effects of multiple factors, and the governing mechanisms are not yet fully understood. To investigate the coupled effects of muddy water sediment concentration (ρ), physical clay content (d_0.01), applied nitrogen concentration (N), and pressure head (H) on infiltration characteristics during film hole irrigation, this study conducted an indoor soil-box experiment using an orthogonal design to analyze soil water and nitrogen transport dynamics. Results indicated that sediment properties were the dominant factors governing infiltration, with their relative influence on cumulative infiltration following the order ρ > d_0.01 > H > N. ρ and d_0.01 strongly inhibited infiltration; for instance, an increase in ρ from 3% to 9% reduced the initial infiltration rate by as much as 49.3%. Conversely, H and N exhibited a slight promoting effect. High muddy water sediment concentration and physical clay content significantly restricted water and nitrogen transport, causing substantial amounts of ammonium nitrogen (NH₄⁺-N) to be retained within the surface soil layer adjacent to the irrigation hole. Paradoxically, the same factors that reduced infiltration (ρ and d_0.01) led to a significant increase in the average change in volumetric water content (Δθ) within the wetted soil volume. Based on these findings, multivariate power function models were developed to predict key parameters. The models demonstrated high predictive accuracy, with coefficients of determination (R²) of 0.9715 for cumulative infiltration, 0.94 for wetting front migration, and 0.9758 for Δθ, and validation errors were within acceptable limits. In conclusion, the film hole irrigation process is predominantly governed by physical clogging from sediment particles, a mechanism that decisively controls the spatial distribution of water and nitrogen. Furthermore, the slight enhancement of infiltration by nitrogen fertilizer suggests a potential physicochemical mechanism, possibly involving ion-induced flocculation of clay particles. The models developed in this study provide a quantitative basis for precision fertigation management in China’s Yellow River irrigation district and other regions with similar conditions. Full article